This video is rich with insights into living with an A2A system. Thanks for sharing! Perhaps as more people move to heat pump systems in whatever form that takes, we will all begin to adopt this approach of heating always on instead of the on/off mentality we've all been raised with which does seem to be a hangover from gas and oil boilers. For reference an A2W heat pump would probably never modulate down to that low 300W. My 7kW Vaillant modulates down to ~600W. Some of the smaller A2W heat pumps will modulate down to ~450W. Another win for the A2A system. Keep up the great work!
Thanks! I think the 5-way split would probably go to a minimum somewhere in the 500W range, so not dissimilar to your Vaillant. I just wish it would do longer cycles rather than switching on and off every 10 mins! It's probably due to the lower thermal capacity of the refrigerant compared to the water running through a load of radiators. I'm tempted next year to adopt a 24hr on strategy with setback temperatures instead, but I'll keep going on this strategy for the rest of this winter to get a proper set of data for comparison.
I think this video is something @heatgeek would like, with its information on A2A in real-life use? They are fairly sceptical about A2A, but this shows someone happily living with it. Also, is there not an anti cycling setting?
Hi, I have a 5 way Toshiba unit with 4 indoor hinari units and a spare way if required, mainly because of your very informative videos. I run my system fairly similar to the way you run yours but I set it back to 19’C overnight and back to 22’C on two rooms during the day and are quite happy with the power usage. One very important thing to note with the 24hr running on older houses like mine (1960’s build fairly large detached bungalow) is you do not have any condensation problems or cold spots in the house. Before I installed the AtoA I put a temp/humidity monitoring system in every room and a power measuring system on the AtoA outdoor unit (all sonoff equipment) which was quite inexpensive but gave me an excellent centralized overview of what exactly was happening in my property. After a few different running scenarios like you I quickly came to the realization that fairly constant running produced a far more comfortable ambience for very little extra power cost with a far greater reduction in humidity/condensation throughout the house due to fairly steady temps. I don’t have a battery but do flex my Octopus Intelligence Go charging to keep my power cost as low as possible but will probably fit a battery at a later date due to the prices dropping. I still have gas water heating and was thinking about a thermal store but over the last few weeks have read that you will soon be able to request a gas supply with no standing charge but a very small additional price per Kwh use so that heat store is on hold to see how this pans out. Love the videos and the info but some of your more complicated spread sheets addle my brain😂 Thanks for all the valuable info.
That's great to hear, I'm really pleased it's working so well for you. I've been watching battery prices with interest recently and if they come down much further I'm very tempted to add a few more kWh. Just a little bit lower and I'll pounce.
@@TimAndKatsGreenWalk A possible good idea for a vid could be condition based monitoring of the outdoor unit using the phone apps for measuring vibration. These days nearly all phones have an accelerometer which can show you deterioration of rotating equipment bearings over time, it's good to see a problem long before it arrives as a critical problem in the middle of the heating season.
Over the last year since installing A2A we have been running it on demand which clearly was working the system hard to heat the house in the evenings, so the indoor units tend to run at higher fan speeds (which is very noticeable in the background) and the house was not that comfortable. Frankly, had been quite disappointed with the system. Since watching, have switched to running overnight at 21 degree C during Intelligent Octopus hours then running during the day at 18 degrees C. The house is obviously noticeably warmer and much more comfortable and the indoor units are running quieter. Most impressively, we are only using a bit more power and mostly during off peak hours. Thank you!
No problem, I'm glad that strategy is helping. I've been surprised so far that we've not used much more energy than before but it's been cheaper because more of it has been at off-peak rates. It feels like cheating somehow!
Hi Tim, more good information on your system energy usage. We have a similar Panasonic 5 way multi-split system which we have had for about two years, after much testing and monitoring we made a decision to add two electric storage heaters in the core living areas, this enables us to charge these units overnight on the 7pence tariff and allows the home batteries to run the A2A system in the evenings when the storage heaters have discharged most of their heat, therefore minimising our grid use of the peak rate energy. This additional capital expense we feel was money well spent and has enabled us to reduce our annual cost (although consumption on off peak is up) and reduce our reliance on the grid when demand is greatest.
I'm not sure what the relative benefit of using storage heaters charged overnight is vs using a heat pump at peak times. Given the heat pump should be 3-4x more efficient than the storage heaters it should work out roughly cost neutral, I'd have thought. Although I take your point about using less peak power to help the grid out. I'll have to do some analysis on that one to see what the carbon impact is too. An interesting strategy!
This is my 1st winter with A2A and i found that just leaving it at a set temp all the time 24/7 is the best as when i turn it up or down i can see the energy going up and then takes a long time to get to a comfortable temp for me , i have the blades pointing down and the fan on 1 , When the house is warm i find im using less power . last monts Bill was just over £30 something so im pleased with it and i think that next year i might try to keep the house even warmer. im just fed up with no sun at all the weather pattern is definitely changing . Where are the sunny frosty days that i have always found it to be warmer than a dark windy day.
A little bit of sun makes a huge difference to our heating, as we've got such large windows. The battery can last all day even if it's cold when there's a bit of sun to help with both the solar gain and keeping the batteries topped up.
@@TimAndKatsGreenWalk Definitely when the sun is out all day until sundown i use so much less when its recharged at 00.30 . And im sure i have that SAD illness
Very good advice to go low and slow for A2A. We have a Mitsubishi mini split in our lounger for summer cooling (using solar energy) and part time heating. It is much more energy efficient when I step up the room temperature gradually, typically a target temperature 2-3 degrees above room temp. And then repeat if necessary. Your off peak heating is helping to balance the grid as well as lowering your cost, so a Win Win. 🙂
I really appreciate your sharing of these details. I also have a Toshiba Multi-split; 1 pump and four wall units. It's capacity is way more than we need to keep the house warm unless it's really cold. Ours seems to run happily using the "silent2" and power "50" settings. Max power draw like this is about 750 Watts. This might help you with the "cycling", because it does dampen everything down, making changes slower and less erratic, and it reduces noise and wear on the pump. I'm on intelligent flux atm, but I'm going to try octopus go next. Thanks again.
Hmm, I don't seem to have the power 50 setting. Is that the one labelled POWER-SEL in the app with a bar below broken into three chunks? I'll have to do some more experimenting.
@@TimAndKatsGreenWalk Yes, that's the one. Important: you need to set these settings (P50 and silent2) for ALL your wall units on the mulri-split pump you want to try. Similar to they all need to be cooling or heating. silent2 on my phone app requires you tap the house like symbol twice, 1st tap gives silent1 and symbol lights up, second tap gives silent2 symbol still lit, third tap symbol goes out and your back at "normal". Good luck :) p.s., maybe try it on your AC front first
Power 50 will reduce the maximum power the outdoor unit will use, but it doesn't cut the typical power use in half. It's intended if it's installed it on a circuit breaker that doesn't meet the recommended amp requirement. It can somewhat help with a low and slow strategy if your firing up from cold often and prepared to wait for longer heat. Silent 2 actually reduces the power the inverter uses in normal operation by limiting the fan speed of the outdoor unit. I tried them all and found running in Auto gets to that low consumption position anyway, eventually once all rooms are warm.
Hi Tim, another great video and obviously very interesting for me as I have the same system but with 8 units in total spread over 2 external fans (2 x 4.5 indoor and 6 x 2.5 indoor). This is my second winter with this setup and I'm still adapting and trying to get it to a comfortable balance. I use a lot of energy but the cosy tariff is great for loading my batteries and then using that cheap power during the peak. My Cheap rate versus normal day rate is in the high 60% and the Peak rate has only been 1.2% over the year. The bottom line for me was that my old Oil boiler that heated the house and a how water tank was costing me between £1400 and £1600 per year which also had the worry of ensuring I didn't run out of oil in the middle of winter ! and the Oil companies only do minimum drops so its was approximately £700 for each tank top up. My average cost over the year for all electric was 0.19p my electric heating (A2A) was 3765 kWh over the year at a cost of £715 and my hot water was 777 kWh at a cost of 147.63 so a total of £862.98 for all heating and hot water compared to previous years of circa £1400. The Hot water is my Edal all in one ASHP 270ltr Water tank which has done really well. The house is a large 5 bedroom, with 5 rooms downstairs, 2 adults that work from home each day and 2 teenage girls that think electricity grows on trees and everything must be turned on at all times and doors must always be left open !! lol the change from Oil to A2A has been a positive one for me and I think my weather up here in the Scottish highlands is probably a tad cooler than down south ! and the house is not great for insulation but Im increasing that room by room as I renovate.
That's very impressive, Bob, it just goes to show what can be achieved. I suspect I've got a few more experiments left to try out but I'll complete this winter using the current strategy and maybe try something different next winter, we shall see. I've got to say that with our gas boiler previously we were never as comfortable as we are now, so I'm really glad we went down this route.
Would love to see a video relating to planning if more than one unit is fitted. Was thinking about having a small air to air unit after installation of an air to water.
Well, if these proposals are to be believed you will be able to have two heat pumps, if you're in a detected home. When the full details are published I'll do an update.
Great video again, thanks for sharing. Might be worth setting a higher temperature overnight for the downstairs rooms in colder periods. An option in order to try and get better COP might be to set it at 21 at 12:30, then 22 at 1am or later, maybe even try a ramp up over the night like an A2W water cycle?
I'm not sure I have that many schedule slots to play with, I'll have to check. So far 21 has been ok, but we've not had a really prolonged period of cold yet so we'll see how it goes.
Yup, I just checked and there are only those four slots, so we couldn't set up a ramp in that way, unfortunately. I've no idea why it's limited to only four slots.
@@TimAndKatsGreenWalkit's a large investment of time so probably not worth it on its own but I control our system with Home Assistant instead of the Toshiba app now; you can control it with a widget that looks like a standard thermostat, but it also means you can have as many timer slots as you like, and you can turn on and off different timers really easily if you're doing different things like going away. You can also use timers to change different aspects individually like changing the speed setting without changing the temperature, things like that.
That's a really good idea; I just have set my MHI unit downstairs to auto fan @ 21 over the Economy 7 period, and the fan does ramp up quite high, so your suggestion may help and maybe just set the fan to a middle setting (I'm not bothered about the noise but just want the optimum efficiency.
I am having my A2A system installed next week. I have gone for Mitsubishi Heavy Industries units. I have noticed that the smaller units have a better COP. The installer has recommended 2 outdoor units, each running 2 indoor units. The 2 south facing units are together. He said in Winter when the sun was out we probably would mainly need the north facing units and in Summer we would only need to cool the south facing ones. Hopefully that will work in practice.
That's interesting. We have ours split East and West, which is the direction our house faces, so we get a morning/afternoon difference when it's sunny. It's a shame we can't try the two different methods without significant cost, I'd have liked to do a direct comparison between one 5-way split and two 3-ways.
I've been using an A2A unit to heat my office and also noticed some short cycling. I found that when the fan was on auto, it would run at low power when the unit was at low power. That sounds sensible, but it lead to the unit just heating the air on that side of the room and then shutting off. Then 10 minutes later the air would mix, the unit would detect colder air and switch on again. Setting the fan to run at medium speed mixed up the air more, and allowed the unit to run for longer, and then stay off for longer because the whole room was warm. What would be nice is several remote temperature sensors, or an IR camera in the unit, so it can measure the temperature of the whole room, not just the air where it is. That said, it's much more comfortable than when the old 25kW combi boiler would cycle on and off, blasting masses of heat for a while and then waiting until it got really cold.
Yeah, I think you can get external thermistors to help with the modulation, but it's more cost and complexity, of course. Perhaps I should look into that though. I totally agree that it's significantly more comfortable than the gas boiler was, for sure.
One thing to consider to combat short cycling is the use of a ‘follow me’ function. Usually the indoor unit uses a combination of an internal thermometer and heat compensation settings meaning it’ll overshoot by a few degrees on the assumption it’ll be cooler lower down in the room. I found it cycles more frequently using this default setting. When I set the ‘follow me’ feature it feeds in the temperature from the remote so you get longer but less frequent top ups of heat.
@@TimAndKatsGreenWalk You will probably have a P-SEL on your remote which will let you temporarily de-rate the outdoor unit which will limit the maximum current (100%-75%-50%) the unit can take if you feel it oversized and cycling for the duty in particular circumstances.
@@MrKenenglish1 I have actually found that setting and turned it on to 50% to see if it helps. Although that only limits the top end, it doesn't really help with the minimum output levels, but we shall see.
hey Tim, trust all is well, i initiated my EnerPhit project but liked this video as was keen to see what the usage is. my AC is setup: a 10kW outdoor unit and 4x windfree-one way units (3x2.6kW and 1x3.5kW), second winter now and best (at least for me) solution is just to leave them on 24/7 without schedule. we have it set to 21/22 degrees, no shortcycling etc, 2 upstairs dont even turn on as 2 downstairs provide sufficient heat as it rises. Fan mode is always auto (i’d stay away from low etc settings), let the inverter do the job, after 30mins or so goes to lowest speed anyway and maintains that going forward…consumption wise: if weather outside between 6-12 degrees roughly 10kW for 24hrshrs, 0-6 around 20kW or so, heating comes on cca 4 times a day for 2-3 hours (again this all for 21/22 degrees for B epc rated 3 year new build) decided to go enerphit though: mvhr, insulation, airtightness, new windows/doors…keeping the ac setup
I'm tempted to try the 24/7 strategy but I'll probably do that next winter so that I've got a full winter using the current strategy. We seem to have similar energy consumption per day (currently about 19-20 kWh per day with temp about 6 deg outside). I'm curious to see how your EnerPhit project works out, that's something I'd like to do too one day.
@@robert_minarik ironically I don't do LinkedIn! I suspect it'll be a couple of years before I get around to looking into EnerPhit any further but I'll bear your offer in mind, thank you.
We have the same system as you have. But we have a 1:5 multi-split with a single outdoor unit. The main problem I have for this is when you are running only 1 unit, it does lead to short cycling, especially when cooling. So I’ve always wondered if I should have specified 2 smaller outdoor units. Problem is the smallest single outdoor unit with enough ports for 5 indoor units is 10Kw. Really interesting that you’ve had the opposite inclination. I will say though, our system is very efficient in heating mode. It’s just cooling, especially of smaller rooms, it will cycle as it’s too powerful.
We primarily use ours for heating, with all five indoor units being on most of the time, so that was my main reason for thinking a single 5-way split would probably have been better. It's an interesting compromise, I wonder if there's a better way to do both!
@@TimAndKatsGreenWalk I'm not sure it is better to have more indoor units on one outdoor unit. I have 4 units upstairs on one 2.9kw outdoor unit, and 1 downstairs on a 2 kw outdoor unit. The upstairs units all cycle every 10 to 15 minutes, because at least 1 of the 4 has drifted below the set point. The downstairs unit is more or less constantly running on 300 to 400w. I imagine this impacts efficiency. By the numbers, my upstairs unit uses twice as much energy, though the floorspace it is heating is only slightly larger than the downstairs unit.
@@aluminumfalcun I'd love to do a proper test with this but it would require replacing our existing two 3-way outdoor units with one 5-way and then seeing how it compares. If I could get Toshiba to sponsor that test then I'd absolutely do it! I really would like to know what the best option would be, as without a proper comparison I'd just be guessing.
Hi Tim, I agree with so many of your conclusions, but a couple of points I'd like to add... I have 7 internal Daikin a2a units (+1 in garden building), mainly fuelled right now (mid December), during peak times, by a 20Kwh MyEnergi Libbi. A Sunamp thermal battery heats the water, topping up, like the Libbi, using the Octopus Intelligent Go 6hr time window. Everything links (including Zappi etc) together in the Myenergi eco system. But I don't experience the 'cycling' problem you describe with the Daikin Stylish units I have throughout. Crazily, for a slightly rambling 5 bed house, I have 4 external units (2 single splits & 2 multisplits), because I built it all up gradually without a master plan! If I started again I'd probably have just 2 multisplits. But none of the internal units seem to 'cycle'like you describe. Maybe that's just not a characteristic of the Daikin units. Or perhaps it's because, if I leave them on a low fan setting, I can use a feature called 'Demand Control' that moderates the energy usage of the external unit. I think, if you are able to hide them from view (in alleyways, on flat roof rear extensions etc) it's not really a problem having more than one outside unit. Because: 1) A/c engineers generally price servicing costs per inside unit regardless of how many outside units you have. 2) If you match internal units well to the external (taking into consideration how much & when you use them etc), you may not often be using more than one condenser at any one time. 3) Here's a big one - resilience. If one condenser goes down you've still got at least one other operating. So best to make sure, for example, if you have 2 living rooms, they are on separate condensers. You can't enjoy thst benefit with a big a2w system. 4) As you know, depending on house size and/or layout, the pipe runs can become impractical, if not impossible, using a single mutisplit condenser.
Oh, absolutely, there are pros and cons to having multiple external units, for sure. The resiliency benefit is a big one, but I'm pretty sure it would have been cheaper to install if we'd had just the one 5-way multi split. Even so, it's working pretty well for us, so I can't complain, I'd just be curious to know how it would have compared doing it the other way, for my own curiosity as much as anything else.
Simon, thanks for sharin, I'd love to know more about your sunlamp as it was one of the solutions that I looked at before I settled for the water cylinder all in one with ASHP on top. My worry was that how much power would it use to heat up the eqivalent of a large water tank to accommodate 2 teenage daughters and a the other half as she likes a bath every so often ! me Im 5 mins in and out of the shower and Im done !! lol (ex army. Do you have stats for usage and what the cycle is like when you run it. Thank you
I'm afraid I have no stats yet because the Sunamp only went in a fortnight ago (& the boiler + rads are now taken out). However, it seems to complement an a2a solution well, & it delivers quicker than the old Worcester combi (when I ran the latter in 'eco' mode). As for running out (I remember what Saturday nights were like when my daughters still lived at home!) of hot water, I don't think there'd be any difference from a cylinder (or from a Mixergy, that was the alternative I was considering). The Sunamps are sized to match common cylinder sizes. Beyond the small size the clincher for me was: 1) the heat loss on Sunamps is much lower than a cylinder. That's important if there are irregular, sometimes long gaps, between your running hot water. The house here is often empty. 2) Claimed as completely maintenance free. 3) Will last me out The stats on the last 2 points will take a decade or so to produce! There was little or no difference on purchase/installation cost, for me at least, between the Mixergy & the Sunamp+Eddi.
A random thought about having two outdoor units. What about a multisplit A2A for most rooms where it's nice to have the option of variable temperatures or cooling and a small A2W for hot water and rooms where A2A isn't suitable (eg bathrooms). I suspect it would be much more expensive to buy/install but could get around the issue of needing some sort of resistive heating in bathrooms and where to site a hot water cylinder with an integrated heat pump. Although my garage is attached to the house its average temperature over the last 30 days has been 4.2, with a couple of drops below freezing so not really comparable to your cosy garage! The A2W could also be working almost exclusively overnight in winter or middle of day in summer with solar.
I did wonder about that at one point but as you say it would have been complicated and expensive to do. The towel rails are only on for an hour a day (and in fact we only use the one in our ensuite unless we have guests) so actually use very little energy, and it's all at off peak rates so costs even less. I think the absolute ideal combination would be A2W powered underfloor heating downstairs (and bathrooms) with a ducted A2A system upstairs.
On the point of whether to have a 1x5 multisplit rather than two 1x3 multisplits there's another thing I think may be worth considering. My 2nd multisplit (actually still in boxes, about to be installed) will serve the rooms I rarely use, ie spare rooms & hall. The other serves rooms often in concurrent use. My theory is that the latter will be operating more efficiently than the former. But the former is not used much. Maybe this is a good idea for configuring a 'double multisplit' system?
My main reason for thinking a single 5-way would have been better for us specifically is that we could definitely have configured it in that way and saved ourselves the cost of two external units. In some situations the pipe runs alone make a single unit impractical though, so there are definitely cases where more than one external unit would be necessary. But I think for us we could have managed with one.
The dehumidifiers are set to come on for a couple of hours overnight, but recently they've not been operating as the humidity has been lower than their set point, so they've not turned themselves on.
The issue I have with bumping up the indoor units is the issue of more points of failure, if you have an issue on one (like Nigel did with the - albeit external - condensate pump), it takes out the whole system. At least with multiple outdoor units you have some degree of redundancy. The 5-port unit also is less efficient overall, rated SCOP of 4.08 "A+", vs 4.44 "A++" of the units you have. The other option for your situation would have been smaller outdoor units. Going by your other video you have 2x7.5kW outdoor units, which you could have had 2x the 5.2kW outdoor units instead. There's also a potential gain there as well of (with strategic placement of indoor units), running the entire house heating off a single outdoor unit. The 2 port unit of the 5.2kW unit also has a lower minimum heat output of 1.3kW vs 1.9kW of the 3 port 5.2kW unit, so that could have been an option for optimisation as well. I can't remember if you've said how the units were spec'd, was it just to your requirements? or did the installer size it based on cooling?
I used the cooling rating of the indoor units to define the outdoor unit specs, with the indoor units being suggested by the installer. Had I known more about our heat loss at the time I would have specced lower. As you say, the redundancy of two outdoor units is handy but I think the single 5-way split would have worked out cheaper to install than two of the lower rated 3-way splits (or a 3 plus 2-way split), so despite the slightly lower SCOP I think we'd have been better off overall with the 5-way. With less cycling the 5-way would gain in efficiency in the milder months so perhaps would actually work out more efficient too, it's hard to tell for sure.
Good video it’s a shame that they’re no subsidy for A2A probably down to worries of running AC in summer. We really need fire and forget systems though for 90% of the population
I totally agree, it's daft that the BUS grant excludes A2A. I think you're right about the summer AC use being the reason, although once we all have solar we'll need something to soak up all the excess! I really think that A2A could fill a lot of gaps left by homes where A2W is impractical.
I believe there are plans to include A2A following the budget, under the warm homes plan. Also a few other changes such as removing the 1m from the boundary rule.
With regard to the cycling, I'm surprised that the units don't run a bit longer and then turn off a bit longer rather than the short cycling. Ideally, the on/off times would be programmable for individual customization. My A2W heat pump seems to cycle for periods of about an hour or even several hours when it can't get the output low enough, though I've seen other heat pumps where A2W fast cycles like yours. Certainly on an A2W in a house with high thermal inertia you don't notice any change, I'd assume your A2A would be reasonably comparable if the firmware enabled it.
It's the thermistors for return air, they are installed inside the chassis. One unit with a higher requirement, causes the others on the multisplit to overheat and cycle off, you can relocate them outside the chassis for more accurate sensing, this reduces the short cycling and allows for more consistent use. An amount of extra cable is coiled inside to allow this to happen. It takes about 10 mins to sort it per unit.
If I could then I would probably adopt the same strategy but my 10kWh battery can’t support my energy use for the remainder of the day, so I am on the Cosy tariff which works perfectly for me and negates the need to invest in more battery storage. However I shall have to reassess my optimum configuration when my EV arrives (on order). It’s such a shame that V2X is dragging its heals otherwise the solution would be simple (fill up everything overnight). Regarding A2A efficiency, do you know whether running at a lower output temperature to the house is more or less efficient? I don’t know the details of the inner workings of the units, but if the discharge pressure of the compressor is lower then the energy will be lower and the efficiency higher (would need to explain this via a P-H Mollier diagram). If however the units operate at a fixed discharge pressure then the efficiency would be more or less constant (some variation due to external conditions). 🤓
I believe they run more efficiently if you set a lower temperature, much like A2W systems. I've pointed my thermal camera at the indoor units and they do seem to run cooler when the indoor set point is lower too.
Hello Tim - I have the 5 way multi split system you desire installed 14 months ago, inspired by you and theevpuzzle. Does your energy monitor for total consumption per unit work in the application? Mine does but my outdoor unit is an updated model from yours that came out in October 2023. I love the system and wouldn't go back. Cycling when it gets to temp is annoying though, the min power draw in that state is 550w. I wish there was a way to automate the turn off once it reaches that behaviour without resorting to the home assistant automation that I still haven't found time to write.
No, the energy monitoring doesn't work for us in the app, annoyingly, I guess that was added to the updated model that you got. I'm really glad it's working well for you, that's very gratifying. The cycling is annoying, for sure, but not so much that I'd ever go back!
Question for you Tim, why is the lounge unit overshooting its setpoint of 19c? Unit should turn itself off and sit waiting for the temp to drop it shouldn't overheat the room. Have you also tried just heating to 19c 24/7. I have a 5 unit multi split by LG, yours ramps lower down than mine. You would be best just leaving them all set at an even temp all the time which may reduce cycling.
The room unit itself does shut off, but there is still hot refrigerant running though it as the other units are still running, so periodically the fan will come on for a few seconds and dump some heat into the room. I've no idea why it does it this way, I didn't design the system! But it's not a big deal as we actually want the room at 21, we just set to 19 because we know that will give us the temperature we want. I'm thinking I'll try 24/7 heating next winter as a comparison but I want a full winter of data using the current strategy so that the comparison is fair.
With the knowledge you have gained over the years be it from past mistakes or things you hadn’t thought of when starting out on your journey, putting all of that together what would you advise or not advise for a beginner in regards to starting out with their journey.
Oh, crikey, that's a big question. I might have to defer that to a whole video. It does sound like a good topic to cover that other folks could benefit from, I'll add it to my list!
@@TimAndKatsGreenWalk I only mentioned the naughty list with farther Christmas in mind because I must be the world’s longest member of being on the naughty list , bright side at least I didn’t get a present that was not wanted.
@@KavanOBrien you know, I always used to get quite stressed at Christmas with the thought of getting an unwanted present. So much so, in fact, that a number of years ago I insisted that I no longer wanted to receive presents for either Christmas or birthdays. It works very well!
An interesting aspect of heat pumps is that they can heat up the house really effectively and efficiently when it is around 7C outside. Then when the cold spell hits let's say 0C for 3-4 days it makes a huge difference if the house was kept toasty going into a cold spell. So yea, I totally agree with your methods, it uses more night power, but to delay heating with a heat pump until there isn't any heat to pump is just not very smart. If you have historical gas data, have a look, I bet your gas consumption was lagging behind the cold spell by a couple of days. This behaviour really doesn't work well with heat pumps;)
I did some modelling for our first winter of heat pump use and found a definite correlation with the previous day's temperature as well as the current day's temperature when it came to heat pump energy consumption, so I totally agree that there is a time lag component to heating. That's true regardless of the heat source, as you say. Keeping the house thermal mass topped up certainly helps to smooth out the acute energy demands.
It's a good point mjp0815. My a2a units were struggling a bit when we had a really cold snap a year or so back: minus 5 on a few days. They stop periodically to go through a defrost cycle on the outside units. Now, though, I have more a2a units, & with adjoining rooms running off different outside units, I can open a door between the two rooms to help things along a bit. But there were maybe 3 or 4 days when I had to put on an electric fan heater in the living room. And I an electric blanket came in handy! There again, that happened occasionally with the wet system in the living room where I hadn't supersized the rads. Those days are very few here in the South though, 99% of the time my (Daikin) units manage fine, if running at well under 5 COP, I reckon, when the temperature is below 5 degrees. I'd be more doubtful in the Scottish Highlands. I also find I make good use of electrically heated tiled floors in the (very small) bathrooms. Some 'tactical' conventional (ie SCOP 1 rather than 5) electric heating in very small rooms is a good idea if, lile me, your house is not open plan, with a lot of (mostly small) rooms.
Hi, I understand that using a low fan speed is quite comfortable, but it actually increases electricity consumption significantly-up to 35% compared to high fan speed, as I have noticed. Here in CEE, nights are frequently below 0°C, and since this would activate the protective heating within the outdoor units (80-120W per hour for each outdoor unit), we heat the house up during the daytime when it's warmer outside and efficiency higher, and turn off and isolate the air conditioners from the grid during the night.
Thanks Tim another very helpful and informative video. I have a similar Toshiba system. Just wondering, do you find there is good correlation between energy use recorded on your GivEnergy smart plugs and the energy use provided on the Toshiba app? As the app is the only way I can gauge my energy use. Many thanks.
Annoyingly that energy monitoring doesn't seem to work on our system. It says "Selected AC model does not support energy data". I have no idea why. I think it's because it's a multi-split, although if you have a similar system and you're able to see that data perhaps they updated it after I had mine installed.
@@TimAndKatsGreenWalk I don't think it's because it's a multisplit, my Daiseikais say the same, and they're 1:1 units. I wonder if it's a purchased addon.
@@TimAndKatsGreenWalk its not it only works for a single unit for our model as that is simple to show as its just the indoor unit and the external fan that is using the power. Ive thought about monitoring the electrical use at the indoor unit level but at that point it gets to what value is it giving me and just another bit of data to ponder over ! haha
Hello, nice video! What's the reason for not setting the fan speed to highest or second highest setting during the night? I found that it's much more efficient to have higher fan speeds. It seems to me that my unit is using slightly less electricity and the air temperature leaving the indoor unit is lower, meaning that we should get a better efficiency.
I don't think the actual refrigerant temperature is any cooler when the fan setting is higher, but I could be wrong. There is a small extra energy draw with the higher fan setting and a lot of extra noise, so I don't really want the fans on full blast overnight. I am experimenting with the auto fan overnight, however, to see how that goes.
Fans in higher speed will mean the room reaches temperature quicker and then cycle off... low and slow/constant is best. Unit will also ramp up if fan speeds are higher as more heat is being rejected into the room by the indoor unit.
@TimAndKatsGreenWalk Well from my laymen understanding it should be easier to evaporate the refrigerant if it already comes into the evaporator cooler, as we need to drop its temperature below ambient, otherwise we can't use it as a heat pump. This means that the compressor can run on a lower pressure gradient and uses less power. I also think that the input refrigerant temperature at the high side stays constant but with an overall higher efficiency. I haven't dug into the actual physics of it though and my explanation is no doubt oversimplified. I found that the auto setting is mostly tuned for comfort and I got significantly higher air temperatures blowing out of the unit than with a high fan setting, which definitely hurts efficiency.
@@richardc1983 But the unit will cycle anyways if the heat loss of the room is lower than its mimimal output power. Just that with a lower fan setting you are hurting the efficiency of the unit, rendering its minimal heating power a bit lower but with a lower efficiency. That's at least my understanding of it. It's really hard to measure these things properly.
I think the option to set a target heat then another lower target before turning back on would be a good idea for both a2a and a2w if system is at minimum output is causing cycling.
@@robertredpath4817 yep everything I've seen is cycling kills efficiency, would be good if these could have target temperatures. I currently run storage heaters and a fluctuation of a few degrees isn't actually an issue. You don't need to keep temp at like 0.5c accuracy to remain comfortable. Still not sure what I want to do on renovation a2w with underfloor heating or a2a mini split to also get AC, a2w higher cop but more complicated design and haven't seen any also do AC.
We have a ducted A2A system so we can't really zone in the same way. In the first year I tried a schedule with more conventional setbacks like gas heating. It worked but the system was working hard to make heat at 4am and outdoor temps of -10C, not ideal for COP. This year I set the heat to one temperature 24/7. So far it doesn't use a lot of power at peak times, so not expensive. If I understand your system vs. A2W, you don't have weather compensation?
A2A sort of does weather compensation by default, it'll provide less energy when it's milder outside. I'm thinking I'll try 24/7 heating next winter as a comparison, but will complete this winter using the current strategy to get a full set of data.
@@TimAndKatsGreenWalk It's not quite weather compensation. It's more like load compensation, where the system uses the outside temperature as a data point to adjust output based on the current load whilst also responding to factors such as room temperature. Weather compensation, on the other hand, adjusts output proactively based on the outside temperature to meet forecasted heat demand. Similar outcomes, but achieved differently.
I am thinking of installing a battery and solar system but not sure if I would need a backup system what do you have any help would be appreciated thanks (great video by the way)
You mean a backup heating system or power-cut backup for the batteries? We've never needed any additional heating even when it's super cold outside. But we have a couple of fan heaters from before when we used to have a gas boiler, which we've never used.
@@Lau-s6p gotcha. Well, we have this system: th-cam.com/video/HD5KqC7Mfv8/w-d-xo.html But nowadays you can get much better whole house backups by installing a GivEnergy All In One battery system, or Tesla Powerwall 3, for example, which come with "gateways" that automatically switch to battery power in the event of a power cut (there are other systems too but those are good ones to look into).
Another great video. Couple of questions. You talk about the set temperature over shooting? doesn't the room thermostat control this without you having to manually switch off? Also is there any control of the temperature of the warm air emitted from the units or is it only the fan speed that's adjustable? If the air temperature is fixed typically what is this? Thanks
You can't control the temperature of the air coming out of the units directly, only the fan speed, although by setting a lower room temperature the air coming out of the units does tend to be lower too, from about 40 at its maximum, down to 30 or so when not much heat is required. When I say overshooting I mean that if I set the temperature to 19 the room ends up at 20 or 21, for example. The units themselves have an internal thermistor, they don't have an external one (or at least ours don't, you can get ones with external thermistors), I use independent thermometers to see what the room temperatures are. The issue with multi-split systems is that the rooms can all be different temperatures, so if only one of them requires heat the external unit will be on, and so a trickle of heat is always getting provided to the other indoor units connected to the same outdoor unit, even if they are off themselves. Only if all the indoor units connected to a single outdoor unit are at or above temperature then that's when the outdoor unit turns off, or starts cycling.
@TimAndKatsGreenWalk Thanks Tim. So the control for the room temperature is within the unit which is usually at a high position close to ceiling? In that case it will be influenced by the air temperature at that point being at a higher temperature than where we sit or stand. Correct me if I'm wrong that doesn't appear sensible one would have to work out some sort of offset factor? Have I completely misunderstood 😕
@@jonnythompson2711 yup, that's pretty much it. You can get external thermistors we just don't have them for ours. Apparently you can remove the internal ones and site them away from the units, which can help. There a lot of other factors that can affect it like the size of the room etc. and some overshoot more than others, some don't overshoot at all in fact. It's also constantly pulling air in and blowing it out, bear in mind, so the air gets pretty well mixed in the room, although I'm sure it's not totally uniform. Generally it's not an issue as you just set the temperature controls to whatever results in the intended room temperature, so we set to 19 if we want 20-21, say, and that's fine. It's a lot easier than trying to tinker with radiator valves, that's for sure!
@TimAndKatsGreenWalk Thanks for explaining that and I'm sure one could adjust accordingly. Just one last thing you say there's no direct control on the temperature of the warm air being emitted? If that's the case is this one thing that a2a can't do and a2w can? I fully appreciate that it's not at all efficient but having that ability to raise the flow temperature if absolutely necessary could be reassuring.
Actually, out of interest I just used my IR thermometer to measure the temperature of the floor and ceiling in the office where I'm sat and it's 20.8 on the floor and 21.8 on the ceiling.
I do similar with our A2W system, but only on the lower floor, which has under-floor heating (eg a huge emitter) and it's working very well. What I'd like to try and work out is, although it's definitely cheaper to thermally charge the house at 7p/kWh versus 26.72p/kWh, I'd be curious to see the COP differential between say, running the ASHP at midnight vs midday (when, typically, it would be a few degrees warmer outside...)...do you have this data?
I don't have that data, sadly, no. It is a very interesting question though, and one I'd like to understand more about. There definitely will be a small difference in COP but I don't think it'd be enough to make the overnight heating strategy any less beneficial.
@@TimAndKatsGreenWalk agreed, I cannot concieve of it ever working out more expensive, seeing as the cost per unit is nearly a quarter of the price! I just want the stats!
It’s not THE most financially viable option, but I strongly advocate for getting batteries to cover your highest average daily usage without factoring in panels. Ignoring the 5-10 days a year it’s obscenely cold etc. Being independent and power cut proof, at least in my mind, was worth the extra cost. April - October, where solar is reasonably reliable, you can set up an export schedule to abuse the import tariff and offset the cost.
I think we've got just about the sweet spot of battery capacity for our needs, balancing battery cost with savings. I did a whole video about it, in fact: th-cam.com/video/_qysulne5g0/w-d-xo.html That's not to say I wouldn't love more capacity, but at the moment I can't really justify it. If battery prices halved then I would absolutely get another 5-10 kWh.
This video is rich with insights into living with an A2A system. Thanks for sharing!
Perhaps as more people move to heat pump systems in whatever form that takes, we will all begin to adopt this approach of heating always on instead of the on/off mentality we've all been raised with which does seem to be a hangover from gas and oil boilers.
For reference an A2W heat pump would probably never modulate down to that low 300W.
My 7kW Vaillant modulates down to ~600W. Some of the smaller A2W heat pumps will modulate down to ~450W.
Another win for the A2A system.
Keep up the great work!
Thanks! I think the 5-way split would probably go to a minimum somewhere in the 500W range, so not dissimilar to your Vaillant. I just wish it would do longer cycles rather than switching on and off every 10 mins! It's probably due to the lower thermal capacity of the refrigerant compared to the water running through a load of radiators. I'm tempted next year to adopt a 24hr on strategy with setback temperatures instead, but I'll keep going on this strategy for the rest of this winter to get a proper set of data for comparison.
I think this video is something @heatgeek would like, with its information on A2A in real-life use? They are fairly sceptical about A2A, but this shows someone happily living with it.
Also, is there not an anti cycling setting?
@Biggest-dh1vr I've not found an anti-cycling setting anywhere but I'll have another look.
Hi, I have a 5 way Toshiba unit with 4 indoor hinari units and a spare way if required, mainly because of your very informative videos. I run my system fairly similar to the way you run yours but I set it back to 19’C overnight and back to 22’C on two rooms during the day and are quite happy with the power usage. One very important thing to note with the 24hr running on older houses like mine (1960’s build fairly large detached bungalow) is you do not have any condensation problems or cold spots in the house. Before I installed the AtoA I put a temp/humidity monitoring system in every room and a power measuring system on the AtoA outdoor unit (all sonoff equipment) which was quite inexpensive but gave me an excellent centralized overview of what exactly was happening in my property. After a few different running scenarios like you I quickly came to the realization that fairly constant running produced a far more comfortable ambience for very little extra power cost with a far greater reduction in humidity/condensation throughout the house due to fairly steady temps. I don’t have a battery but do flex my Octopus Intelligence Go charging to keep my power cost as low as possible but will probably fit a battery at a later date due to the prices dropping. I still have gas water heating and was thinking about a thermal store but over the last few weeks have read that you will soon be able to request a gas supply with no standing charge but a very small additional price per Kwh use so that heat store is on hold to see how this pans out. Love the videos and the info but some of your more complicated spread sheets addle my brain😂 Thanks for all the valuable info.
That's great to hear, I'm really pleased it's working so well for you. I've been watching battery prices with interest recently and if they come down much further I'm very tempted to add a few more kWh. Just a little bit lower and I'll pounce.
@@TimAndKatsGreenWalk A possible good idea for a vid could be condition based monitoring of the outdoor unit using the phone apps for measuring vibration. These days nearly all phones have an accelerometer which can show you deterioration of rotating equipment bearings over time, it's good to see a problem long before it arrives as a critical problem in the middle of the heating season.
I'll add it my list!
Over the last year since installing A2A we have been running it on demand which clearly was working the system hard to heat the house in the evenings, so the indoor units tend to run at higher fan speeds (which is very noticeable in the background) and the house was not that comfortable. Frankly, had been quite disappointed with the system.
Since watching, have switched to running overnight at 21 degree C during Intelligent Octopus hours then running during the day at 18 degrees C. The house is obviously noticeably warmer and much more comfortable and the indoor units are running quieter. Most impressively, we are only using a bit more power and mostly during off peak hours. Thank you!
No problem, I'm glad that strategy is helping. I've been surprised so far that we've not used much more energy than before but it's been cheaper because more of it has been at off-peak rates. It feels like cheating somehow!
Great information can not beat trial and error thanks Tim 👍👍👍
I will be experimenting until the day I die!
I know you will, and that’s why I will keep following your Vlogs 👍👍👍
@@Glyn001 glad to hear it.
Interesting video. That looks like my best way to go with A2A. Thanks for the info. Rob
No problem.
Hi Tim, more good information on your system energy usage. We have a similar Panasonic 5 way multi-split system which we have had for about two years, after much testing and monitoring we made a decision to add two electric storage heaters in the core living areas, this enables us to charge these units overnight on the 7pence tariff and allows the home batteries to run the A2A system in the evenings when the storage heaters have discharged most of their heat, therefore minimising our grid use of the peak rate energy. This additional capital expense we feel was money well spent and has enabled us to reduce our annual cost (although consumption on off peak is up) and reduce our reliance on the grid when demand is greatest.
I'm not sure what the relative benefit of using storage heaters charged overnight is vs using a heat pump at peak times. Given the heat pump should be 3-4x more efficient than the storage heaters it should work out roughly cost neutral, I'd have thought. Although I take your point about using less peak power to help the grid out. I'll have to do some analysis on that one to see what the carbon impact is too. An interesting strategy!
This is my 1st winter with A2A and i found that just leaving it at a set temp all the time 24/7 is the best as when i turn it up or down i can see the energy going up and then takes a long time to get to a comfortable temp for me , i have the blades pointing down and the fan on 1 , When the house is warm i find im using less power . last monts Bill was just over £30 something so im pleased with it and i think that next year i might try to keep the house even warmer. im just fed up with no sun at all the weather pattern is definitely changing . Where are the sunny frosty days that i have always found it to be warmer than a dark windy day.
A little bit of sun makes a huge difference to our heating, as we've got such large windows. The battery can last all day even if it's cold when there's a bit of sun to help with both the solar gain and keeping the batteries topped up.
@@TimAndKatsGreenWalk Definitely when the sun is out all day until sundown i use so much less when its recharged at 00.30 . And im sure i have that SAD illness
@@rodden1953try SAD lights by brands like Beurer (Lloyds Pharmacy do a rebrand), they can be bought for around £20 online (eBay etc.).
Very good advice to go low and slow for A2A. We have a Mitsubishi mini split in our lounger for summer cooling (using solar energy) and part time heating. It is much more energy efficient when I step up the room temperature gradually, typically a target temperature 2-3 degrees above room temp. And then repeat if necessary. Your off peak heating is helping to balance the grid as well as lowering your cost, so a Win Win. 🙂
Yes, indeed, it's working well. I'm looking forward to showing the full winter's worth of data in due course.
I really appreciate your sharing of these details. I also have a Toshiba Multi-split; 1 pump and four wall units. It's capacity is way more than we need to keep the house warm unless it's really cold. Ours seems to run happily using the "silent2" and power "50" settings. Max power draw like this is about 750 Watts. This might help you with the "cycling", because it does dampen everything down, making changes slower and less erratic, and it reduces noise and wear on the pump. I'm on intelligent flux atm, but I'm going to try octopus go next. Thanks again.
Hmm, I don't seem to have the power 50 setting. Is that the one labelled POWER-SEL in the app with a bar below broken into three chunks? I'll have to do some more experimenting.
Ah, yes, looking in the user manual I think it is the POWER-SEL setting. I'll give that a try!
@@TimAndKatsGreenWalk Yes, that's the one. Important: you need to set these settings (P50 and silent2) for ALL your wall units on the mulri-split pump you want to try. Similar to they all need to be cooling or heating. silent2 on my phone app requires you tap the house like symbol twice, 1st tap gives silent1 and symbol lights up, second tap gives silent2 symbol still lit, third tap symbol goes out and your back at "normal". Good luck :) p.s., maybe try it on your AC front first
@davidbrent3200 yup, I found the settings and am trying them out as you described. I'm interested to see if it helps!
Power 50 will reduce the maximum power the outdoor unit will use, but it doesn't cut the typical power use in half. It's intended if it's installed it on a circuit breaker that doesn't meet the recommended amp requirement. It can somewhat help with a low and slow strategy if your firing up from cold often and prepared to wait for longer heat. Silent 2 actually reduces the power the inverter uses in normal operation by limiting the fan speed of the outdoor unit. I tried them all and found running in Auto gets to that low consumption position anyway, eventually once all rooms are warm.
Great video as always, thanks for the info. Always very high quality. Thanks for sharing your hobby.
No problem. It saves Kat from listening to all my rambles!
Hi Tim, another great video and obviously very interesting for me as I have the same system but with 8 units in total spread over 2 external fans (2 x 4.5 indoor and 6 x 2.5 indoor). This is my second winter with this setup and I'm still adapting and trying to get it to a comfortable balance. I use a lot of energy but the cosy tariff is great for loading my batteries and then using that cheap power during the peak. My Cheap rate versus normal day rate is in the high 60% and the Peak rate has only been 1.2% over the year. The bottom line for me was that my old Oil boiler that heated the house and a how water tank was costing me between £1400 and £1600 per year which also had the worry of ensuring I didn't run out of oil in the middle of winter ! and the Oil companies only do minimum drops so its was approximately £700 for each tank top up.
My average cost over the year for all electric was 0.19p my electric heating (A2A) was 3765 kWh over the year at a cost of £715 and my hot water was 777 kWh at a cost of 147.63 so a total of £862.98 for all heating and hot water compared to previous years of circa £1400. The Hot water is my Edal all in one ASHP 270ltr Water tank which has done really well. The house is a large 5 bedroom, with 5 rooms downstairs, 2 adults that work from home each day and 2 teenage girls that think electricity grows on trees and everything must be turned on at all times and doors must always be left open !! lol the change from Oil to A2A has been a positive one for me and I think my weather up here in the Scottish highlands is probably a tad cooler than down south ! and the house is not great for insulation but Im increasing that room by room as I renovate.
That's very impressive, Bob, it just goes to show what can be achieved. I suspect I've got a few more experiments left to try out but I'll complete this winter using the current strategy and maybe try something different next winter, we shall see. I've got to say that with our gas boiler previously we were never as comfortable as we are now, so I'm really glad we went down this route.
Would love to see a video relating to planning if more than one unit is fitted.
Was thinking about having a small air to air unit after installation of an air to water.
Well, if these proposals are to be believed you will be able to have two heat pumps, if you're in a detected home. When the full details are published I'll do an update.
Great video again, thanks for sharing. Might be worth setting a higher temperature overnight for the downstairs rooms in colder periods. An option in order to try and get better COP might be to set it at 21 at 12:30, then 22 at 1am or later, maybe even try a ramp up over the night like an A2W water cycle?
I'm not sure I have that many schedule slots to play with, I'll have to check. So far 21 has been ok, but we've not had a really prolonged period of cold yet so we'll see how it goes.
Yup, I just checked and there are only those four slots, so we couldn't set up a ramp in that way, unfortunately. I've no idea why it's limited to only four slots.
Probably limited to 4 just to save on memory in the timer. Hopefully it doesn't get much colder.
@@TimAndKatsGreenWalkit's a large investment of time so probably not worth it on its own but I control our system with Home Assistant instead of the Toshiba app now; you can control it with a widget that looks like a standard thermostat, but it also means you can have as many timer slots as you like, and you can turn on and off different timers really easily if you're doing different things like going away. You can also use timers to change different aspects individually like changing the speed setting without changing the temperature, things like that.
That's a really good idea; I just have set my MHI unit downstairs to auto fan @ 21 over the Economy 7 period, and the fan does ramp up quite high, so your suggestion may help and maybe just set the fan to a middle setting (I'm not bothered about the noise but just want the optimum efficiency.
I am having my A2A system installed next week. I have gone for Mitsubishi Heavy Industries units. I have noticed that the smaller units have a better COP. The installer has recommended 2 outdoor units, each running 2 indoor units. The 2 south facing units are together. He said in Winter when the sun was out we probably would mainly need the north facing units and in Summer we would only need to cool the south facing ones. Hopefully that will work in practice.
I also found almost no difference in the price of 2 smaller units and 1 large unit.
That's interesting. We have ours split East and West, which is the direction our house faces, so we get a morning/afternoon difference when it's sunny. It's a shame we can't try the two different methods without significant cost, I'd have liked to do a direct comparison between one 5-way split and two 3-ways.
I've been using an A2A unit to heat my office and also noticed some short cycling. I found that when the fan was on auto, it would run at low power when the unit was at low power. That sounds sensible, but it lead to the unit just heating the air on that side of the room and then shutting off. Then 10 minutes later the air would mix, the unit would detect colder air and switch on again.
Setting the fan to run at medium speed mixed up the air more, and allowed the unit to run for longer, and then stay off for longer because the whole room was warm.
What would be nice is several remote temperature sensors, or an IR camera in the unit, so it can measure the temperature of the whole room, not just the air where it is.
That said, it's much more comfortable than when the old 25kW combi boiler would cycle on and off, blasting masses of heat for a while and then waiting until it got really cold.
Yeah, I think you can get external thermistors to help with the modulation, but it's more cost and complexity, of course. Perhaps I should look into that though. I totally agree that it's significantly more comfortable than the gas boiler was, for sure.
One thing to consider to combat short cycling is the use of a ‘follow me’ function. Usually the indoor unit uses a combination of an internal thermometer and heat compensation settings meaning it’ll overshoot by a few degrees on the assumption it’ll be cooler lower down in the room. I found it cycles more frequently using this default setting. When I set the ‘follow me’ feature it feeds in the temperature from the remote so you get longer but less frequent top ups of heat.
I'm not sure I've got that feature on my units, I'll have to check.
@@TimAndKatsGreenWalk You will probably have a P-SEL on your remote which will let you temporarily de-rate the outdoor unit which will limit the maximum current (100%-75%-50%) the unit can take if you feel it oversized and cycling for the duty in particular circumstances.
@@MrKenenglish1 I have actually found that setting and turned it on to 50% to see if it helps. Although that only limits the top end, it doesn't really help with the minimum output levels, but we shall see.
hey Tim, trust all is well, i initiated my EnerPhit project but liked this video as was keen to see what the usage is. my AC is setup: a 10kW outdoor unit and 4x windfree-one way units (3x2.6kW and 1x3.5kW), second winter now and best (at least for me) solution is just to leave them on 24/7 without schedule. we have it set to 21/22 degrees, no shortcycling etc, 2 upstairs dont even turn on as 2 downstairs provide sufficient heat as it rises. Fan mode is always auto (i’d stay away from low etc settings), let the inverter do the job, after 30mins or so goes to lowest speed anyway and maintains that going forward…consumption wise: if weather outside between 6-12 degrees roughly 10kW for 24hrshrs, 0-6 around 20kW or so, heating comes on cca 4 times a day for 2-3 hours (again this all for 21/22 degrees for B epc rated 3 year new build) decided to go enerphit though: mvhr, insulation, airtightness, new windows/doors…keeping the ac setup
I'm tempted to try the 24/7 strategy but I'll probably do that next winter so that I've got a full winter using the current strategy. We seem to have similar energy consumption per day (currently about 19-20 kWh per day with temp about 6 deg outside). I'm curious to see how your EnerPhit project works out, that's something I'd like to do too one day.
@@robert_minarik ironically I don't do LinkedIn! I suspect it'll be a couple of years before I get around to looking into EnerPhit any further but I'll bear your offer in mind, thank you.
Great video, thanks.
We have the same system as you have. But we have a 1:5 multi-split with a single outdoor unit.
The main problem I have for this is when you are running only 1 unit, it does lead to short cycling, especially when cooling. So I’ve always wondered if I should have specified 2 smaller outdoor units.
Problem is the smallest single outdoor unit with enough ports for 5 indoor units is 10Kw.
Really interesting that you’ve had the opposite inclination.
I will say though, our system is very efficient in heating mode. It’s just cooling, especially of smaller rooms, it will cycle as it’s too powerful.
We primarily use ours for heating, with all five indoor units being on most of the time, so that was my main reason for thinking a single 5-way split would probably have been better. It's an interesting compromise, I wonder if there's a better way to do both!
@@TimAndKatsGreenWalk I'm not sure it is better to have more indoor units on one outdoor unit. I have 4 units upstairs on one 2.9kw outdoor unit, and 1 downstairs on a 2 kw outdoor unit. The upstairs units all cycle every 10 to 15 minutes, because at least 1 of the 4 has drifted below the set point. The downstairs unit is more or less constantly running on 300 to 400w. I imagine this impacts efficiency. By the numbers, my upstairs unit uses twice as much energy, though the floorspace it is heating is only slightly larger than the downstairs unit.
@@aluminumfalcun I'd love to do a proper test with this but it would require replacing our existing two 3-way outdoor units with one 5-way and then seeing how it compares. If I could get Toshiba to sponsor that test then I'd absolutely do it! I really would like to know what the best option would be, as without a proper comparison I'd just be guessing.
Hi Tim, I agree with so many of your conclusions, but a couple of points I'd like to add...
I have 7 internal Daikin a2a units (+1 in garden building), mainly fuelled right now (mid December), during peak times, by a 20Kwh MyEnergi Libbi. A Sunamp thermal battery heats the water, topping up, like the Libbi, using the Octopus Intelligent Go 6hr time window. Everything links (including Zappi etc) together in the Myenergi eco system.
But I don't experience the 'cycling' problem you describe with the Daikin Stylish units I have throughout. Crazily, for a slightly rambling 5 bed house, I have 4 external units (2 single splits & 2 multisplits), because I built it all up gradually without a master plan! If I started again I'd probably have just 2 multisplits. But none of the internal units seem to 'cycle'like you describe. Maybe that's just not a characteristic of the Daikin units. Or perhaps it's because, if I leave them on a low fan setting, I can use a feature called 'Demand Control' that moderates the energy usage of the external unit.
I think, if you are able to hide them from view (in alleyways, on flat roof rear extensions etc) it's not really a problem having more than one outside unit. Because:
1) A/c engineers generally price servicing costs per inside unit regardless of how many outside units you have.
2) If you match internal units well to the external (taking into consideration how much & when you use them etc), you may not often be using more than one condenser at any one time.
3) Here's a big one - resilience. If one condenser goes down you've still got at least one other operating. So best to make sure, for example, if you have 2 living rooms, they are on separate condensers. You can't enjoy thst benefit with a big a2w system.
4) As you know, depending on house size and/or layout, the pipe runs can become impractical, if not impossible, using a single mutisplit condenser.
Oh, absolutely, there are pros and cons to having multiple external units, for sure. The resiliency benefit is a big one, but I'm pretty sure it would have been cheaper to install if we'd had just the one 5-way multi split. Even so, it's working pretty well for us, so I can't complain, I'd just be curious to know how it would have compared doing it the other way, for my own curiosity as much as anything else.
Simon, thanks for sharin, I'd love to know more about your sunlamp as it was one of the solutions that I looked at before I settled for the water cylinder all in one with ASHP on top. My worry was that how much power would it use to heat up the eqivalent of a large water tank to accommodate 2 teenage daughters and a the other half as she likes a bath every so often ! me Im 5 mins in and out of the shower and Im done !! lol (ex army. Do you have stats for usage and what the cycle is like when you run it. Thank you
I'm afraid I have no stats yet because the Sunamp only went in a fortnight ago (& the boiler + rads are now taken out).
However, it seems to complement an a2a solution well, & it delivers quicker than the old Worcester combi (when I ran the latter in 'eco' mode).
As for running out (I remember what Saturday nights were like when my daughters still lived at home!) of hot water, I don't think there'd be any difference from a cylinder (or from a Mixergy, that was the alternative I was considering). The Sunamps are sized to match common cylinder sizes.
Beyond the small size the clincher for me was:
1) the heat loss on Sunamps is much lower than a cylinder. That's important if there are irregular, sometimes long gaps, between your running hot water. The house here is often empty.
2) Claimed as completely maintenance free.
3) Will last me out
The stats on the last 2 points will take a decade or so to produce!
There was little or no difference on purchase/installation cost, for me at least, between the Mixergy & the Sunamp+Eddi.
A random thought about having two outdoor units. What about a multisplit A2A for most rooms where it's nice to have the option of variable temperatures or cooling and a small A2W for hot water and rooms where A2A isn't suitable (eg bathrooms).
I suspect it would be much more expensive to buy/install but could get around the issue of needing some sort of resistive heating in bathrooms and where to site a hot water cylinder with an integrated heat pump. Although my garage is attached to the house its average temperature over the last 30 days has been 4.2, with a couple of drops below freezing so not really comparable to your cosy garage! The A2W could also be working almost exclusively overnight in winter or middle of day in summer with solar.
I did wonder about that at one point but as you say it would have been complicated and expensive to do. The towel rails are only on for an hour a day (and in fact we only use the one in our ensuite unless we have guests) so actually use very little energy, and it's all at off peak rates so costs even less. I think the absolute ideal combination would be A2W powered underfloor heating downstairs (and bathrooms) with a ducted A2A system upstairs.
On the point of whether to have a 1x5 multisplit rather than two 1x3 multisplits there's another thing I think may be worth considering. My 2nd multisplit (actually still in boxes, about to be installed) will serve the rooms I rarely use, ie spare rooms & hall.
The other serves rooms often in concurrent use.
My theory is that the latter will be operating more efficiently than the former. But the former is not used much. Maybe this is a good idea for configuring a 'double multisplit' system?
My main reason for thinking a single 5-way would have been better for us specifically is that we could definitely have configured it in that way and saved ourselves the cost of two external units. In some situations the pipe runs alone make a single unit impractical though, so there are definitely cases where more than one external unit would be necessary. But I think for us we could have managed with one.
Thanks for sharing the nitty gritty Tim, how do you use your dehumidifiers?
The dehumidifiers are set to come on for a couple of hours overnight, but recently they've not been operating as the humidity has been lower than their set point, so they've not turned themselves on.
The issue I have with bumping up the indoor units is the issue of more points of failure, if you have an issue on one (like Nigel did with the - albeit external - condensate pump), it takes out the whole system. At least with multiple outdoor units you have some degree of redundancy. The 5-port unit also is less efficient overall, rated SCOP of 4.08 "A+", vs 4.44 "A++" of the units you have.
The other option for your situation would have been smaller outdoor units. Going by your other video you have 2x7.5kW outdoor units, which you could have had 2x the 5.2kW outdoor units instead. There's also a potential gain there as well of (with strategic placement of indoor units), running the entire house heating off a single outdoor unit.
The 2 port unit of the 5.2kW unit also has a lower minimum heat output of 1.3kW vs 1.9kW of the 3 port 5.2kW unit, so that could have been an option for optimisation as well.
I can't remember if you've said how the units were spec'd, was it just to your requirements? or did the installer size it based on cooling?
I used the cooling rating of the indoor units to define the outdoor unit specs, with the indoor units being suggested by the installer. Had I known more about our heat loss at the time I would have specced lower. As you say, the redundancy of two outdoor units is handy but I think the single 5-way split would have worked out cheaper to install than two of the lower rated 3-way splits (or a 3 plus 2-way split), so despite the slightly lower SCOP I think we'd have been better off overall with the 5-way. With less cycling the 5-way would gain in efficiency in the milder months so perhaps would actually work out more efficient too, it's hard to tell for sure.
Good video it’s a shame that they’re no subsidy for A2A probably down to worries of running AC in summer. We really need fire and forget systems though for 90% of the population
I totally agree, it's daft that the BUS grant excludes A2A. I think you're right about the summer AC use being the reason, although once we all have solar we'll need something to soak up all the excess! I really think that A2A could fill a lot of gaps left by homes where A2W is impractical.
@@TimAndKatsGreenWalk and as if we wouldn’t be using other AC units as we needed it.
@@sebaileyus8043 well, quite.
I believe there are plans to include A2A following the budget, under the warm homes plan. Also a few other changes such as removing the 1m from the boundary rule.
@@chrisdean5176 ooh, I knew about the 1m boundary change, I'd not heard about the A2A changes, that's very interesting.
Hi ,very interesting information. I would like to know how much cost yearly service for air to air. Thanks for video.
It's about £200 for our system, although it would be less if we only had a single outdoor unit.
With regard to the cycling, I'm surprised that the units don't run a bit longer and then turn off a bit longer rather than the short cycling. Ideally, the on/off times would be programmable for individual customization.
My A2W heat pump seems to cycle for periods of about an hour or even several hours when it can't get the output low enough, though I've seen other heat pumps where A2W fast cycles like yours. Certainly on an A2W in a house with high thermal inertia you don't notice any change, I'd assume your A2A would be reasonably comparable if the firmware enabled it.
Yeah, I was surprised by that too, I don't know why the cycling is so short. If I ever find a way to lengthen it I'd like to give it a try, for sure.
It's the thermistors for return air, they are installed inside the chassis. One unit with a higher requirement, causes the others on the multisplit to overheat and cycle off, you can relocate them outside the chassis for more accurate sensing, this reduces the short cycling and allows for more consistent use. An amount of extra cable is coiled inside to allow this to happen. It takes about 10 mins to sort it per unit.
If I could then I would probably adopt the same strategy but my 10kWh battery can’t support my energy use for the remainder of the day, so I am on the Cosy tariff which works perfectly for me and negates the need to invest in more battery storage. However I shall have to reassess my optimum configuration when my EV arrives (on order). It’s such a shame that V2X is dragging its heals otherwise the solution would be simple (fill up everything overnight). Regarding A2A efficiency, do you know whether running at a lower output temperature to the house is more or less efficient? I don’t know the details of the inner workings of the units, but if the discharge pressure of the compressor is lower then the energy will be lower and the efficiency higher (would need to explain this via a P-H Mollier diagram). If however the units operate at a fixed discharge pressure then the efficiency would be more or less constant (some variation due to external conditions). 🤓
I believe they run more efficiently if you set a lower temperature, much like A2W systems. I've pointed my thermal camera at the indoor units and they do seem to run cooler when the indoor set point is lower too.
Hello Tim - I have the 5 way multi split system you desire installed 14 months ago, inspired by you and theevpuzzle. Does your energy monitor for total consumption per unit work in the application? Mine does but my outdoor unit is an updated model from yours that came out in October 2023. I love the system and wouldn't go back. Cycling when it gets to temp is annoying though, the min power draw in that state is 550w. I wish there was a way to automate the turn off once it reaches that behaviour without resorting to the home assistant automation that I still haven't found time to write.
No, the energy monitoring doesn't work for us in the app, annoyingly, I guess that was added to the updated model that you got. I'm really glad it's working well for you, that's very gratifying. The cycling is annoying, for sure, but not so much that I'd ever go back!
Question for you Tim, why is the lounge unit overshooting its setpoint of 19c? Unit should turn itself off and sit waiting for the temp to drop it shouldn't overheat the room.
Have you also tried just heating to 19c 24/7.
I have a 5 unit multi split by LG, yours ramps lower down than mine. You would be best just leaving them all set at an even temp all the time which may reduce cycling.
The room unit itself does shut off, but there is still hot refrigerant running though it as the other units are still running, so periodically the fan will come on for a few seconds and dump some heat into the room. I've no idea why it does it this way, I didn't design the system! But it's not a big deal as we actually want the room at 21, we just set to 19 because we know that will give us the temperature we want. I'm thinking I'll try 24/7 heating next winter as a comparison but I want a full winter of data using the current strategy so that the comparison is fair.
With the knowledge you have gained over the years be it from past mistakes or things you hadn’t thought of when starting out on your journey, putting all of that together what would you advise or not advise for a beginner in regards to starting out with their journey.
Oh, crikey, that's a big question. I might have to defer that to a whole video. It does sound like a good topic to cover that other folks could benefit from, I'll add it to my list!
@@TimAndKatsGreenWalk hope it’s not the naughty list , you should be used to my bad humour by now ,
@@KavanOBrien my list of video ideas 😉. I'll leave it to you to decide how naughty that is!
@@TimAndKatsGreenWalk I only mentioned the naughty list with farther Christmas in mind because I must be the world’s longest member of being on the naughty list , bright side at least I didn’t get a present that was not wanted.
@@KavanOBrien you know, I always used to get quite stressed at Christmas with the thought of getting an unwanted present. So much so, in fact, that a number of years ago I insisted that I no longer wanted to receive presents for either Christmas or birthdays. It works very well!
An interesting aspect of heat pumps is that they can heat up the house really effectively and efficiently when it is around 7C outside. Then when the cold spell hits let's say 0C for 3-4 days it makes a huge difference if the house was kept toasty going into a cold spell. So yea, I totally agree with your methods, it uses more night power, but to delay heating with a heat pump until there isn't any heat to pump is just not very smart. If you have historical gas data, have a look, I bet your gas consumption was lagging behind the cold spell by a couple of days. This behaviour really doesn't work well with heat pumps;)
I did some modelling for our first winter of heat pump use and found a definite correlation with the previous day's temperature as well as the current day's temperature when it came to heat pump energy consumption, so I totally agree that there is a time lag component to heating. That's true regardless of the heat source, as you say. Keeping the house thermal mass topped up certainly helps to smooth out the acute energy demands.
It's a good point mjp0815. My a2a units were struggling a bit when we had a really cold snap a year or so back: minus 5 on a few days. They stop periodically to go through a defrost cycle on the outside units.
Now, though, I have more a2a units, & with adjoining rooms running off different outside units, I can open a door between the two rooms to help things along a bit.
But there were maybe 3 or 4 days when I had to put on an electric fan heater in the living room. And I an electric blanket came in handy! There again, that happened occasionally with the wet system in the living room where I hadn't supersized the rads.
Those days are very few here in the South though, 99% of the time my (Daikin) units manage fine, if running at well under 5 COP, I reckon, when the temperature is below 5 degrees. I'd be more doubtful in the Scottish Highlands.
I also find I make good use of electrically heated tiled floors in the (very small) bathrooms. Some 'tactical' conventional (ie SCOP 1 rather than 5) electric heating in very small rooms is a good idea if, lile me, your house is not open plan, with a lot of (mostly small) rooms.
Hi, I understand that using a low fan speed is quite comfortable, but it actually increases electricity consumption significantly-up to 35% compared to high fan speed, as I have noticed.
Here in CEE, nights are frequently below 0°C, and since this would activate the protective heating within the outdoor units (80-120W per hour for each outdoor unit), we heat the house up during the daytime when it's warmer outside and efficiency higher, and turn off and isolate the air conditioners from the grid during the night.
Thanks Tim another very helpful and informative video. I have a similar Toshiba system. Just wondering, do you find there is good correlation between energy use recorded on your GivEnergy smart plugs and the energy use provided on the Toshiba app? As the app is the only way I can gauge my energy use. Many thanks.
Annoyingly that energy monitoring doesn't seem to work on our system. It says "Selected AC model does not support energy data". I have no idea why. I think it's because it's a multi-split, although if you have a similar system and you're able to see that data perhaps they updated it after I had mine installed.
@@TimAndKatsGreenWalk I don't think it's because it's a multisplit, my Daiseikais say the same, and they're 1:1 units. I wonder if it's a purchased addon.
@@BenIsInSweden hmm, possibly, I don't recall that being an option when I had them installed, but I might have missed it.
@@TimAndKatsGreenWalk its not it only works for a single unit for our model as that is simple to show as its just the indoor unit and the external fan that is using the power. Ive thought about monitoring the electrical use at the indoor unit level but at that point it gets to what value is it giving me and just another bit of data to ponder over ! haha
the toshiba app energy works very close to givenergy on my system. Givenergy AOI and Toshiba 4-way multi-split.
Hello, nice video! What's the reason for not setting the fan speed to highest or second highest setting during the night? I found that it's much more efficient to have higher fan speeds. It seems to me that my unit is using slightly less electricity and the air temperature leaving the indoor unit is lower, meaning that we should get a better efficiency.
I don't think the actual refrigerant temperature is any cooler when the fan setting is higher, but I could be wrong. There is a small extra energy draw with the higher fan setting and a lot of extra noise, so I don't really want the fans on full blast overnight. I am experimenting with the auto fan overnight, however, to see how that goes.
Fans in higher speed will mean the room reaches temperature quicker and then cycle off... low and slow/constant is best. Unit will also ramp up if fan speeds are higher as more heat is being rejected into the room by the indoor unit.
@TimAndKatsGreenWalk Well from my laymen understanding it should be easier to evaporate the refrigerant if it already comes into the evaporator cooler, as we need to drop its temperature below ambient, otherwise we can't use it as a heat pump.
This means that the compressor can run on a lower pressure gradient and uses less power. I also think that the input refrigerant temperature at the high side stays constant but with an overall higher efficiency. I haven't dug into the actual physics of it though and my explanation is no doubt oversimplified.
I found that the auto setting is mostly tuned for comfort and I got significantly higher air temperatures blowing out of the unit than with a high fan setting, which definitely hurts efficiency.
@@richardc1983 But the unit will cycle anyways if the heat loss of the room is lower than its mimimal output power. Just that with a lower fan setting you are hurting the efficiency of the unit, rendering its minimal heating power a bit lower but with a lower efficiency. That's at least my understanding of it. It's really hard to measure these things properly.
That's given me an idea for another video, actually. I can measure this and see what happens.
Interesting video. Is there anyway to say set temp to 21 and then it turns off and doesn't turn back on until it say gets down to 18c.
No, it'll try to keep the room temperature pretty constant, which is actually more comfortable anyway, so that's fine by me.
I think the option to set a target heat then another lower target before turning back on would be a good idea for both a2a and a2w if system is at minimum output is causing cycling.
@@robertredpath4817 yep everything I've seen is cycling kills efficiency, would be good if these could have target temperatures. I currently run storage heaters and a fluctuation of a few degrees isn't actually an issue. You don't need to keep temp at like 0.5c accuracy to remain comfortable.
Still not sure what I want to do on renovation a2w with underfloor heating or a2a mini split to also get AC, a2w higher cop but more complicated design and haven't seen any also do AC.
We have a ducted A2A system so we can't really zone in the same way. In the first year I tried a schedule with more conventional setbacks like gas heating. It worked but the system was working hard to make heat at 4am and outdoor temps of -10C, not ideal for COP. This year I set the heat to one temperature 24/7. So far it doesn't use a lot of power at peak times, so not expensive.
If I understand your system vs. A2W, you don't have weather compensation?
Always best to run a2a, at a constant temp rather than trying to get it to work hard when it's been off.
A2A sort of does weather compensation by default, it'll provide less energy when it's milder outside. I'm thinking I'll try 24/7 heating next winter as a comparison, but will complete this winter using the current strategy to get a full set of data.
@@TimAndKatsGreenWalk It's not quite weather compensation. It's more like load compensation, where the system uses the outside temperature as a data point to adjust output based on the current load whilst also responding to factors such as room temperature. Weather compensation, on the other hand, adjusts output proactively based on the outside temperature to meet forecasted heat demand. Similar outcomes, but achieved differently.
I am thinking of installing a battery and solar system but not sure if I would need a backup system what do you have any help would be appreciated thanks (great video by the way)
You mean a backup heating system or power-cut backup for the batteries? We've never needed any additional heating even when it's super cold outside. But we have a couple of fan heaters from before when we used to have a gas boiler, which we've never used.
Sorry I mean power cut backup @@TimAndKatsGreenWalk
@@Lau-s6p gotcha. Well, we have this system: th-cam.com/video/HD5KqC7Mfv8/w-d-xo.html
But nowadays you can get much better whole house backups by installing a GivEnergy All In One battery system, or Tesla Powerwall 3, for example, which come with "gateways" that automatically switch to battery power in the event of a power cut (there are other systems too but those are good ones to look into).
Thanks very much that's a big help look forward to your next video@@TimAndKatsGreenWalk
Another great video. Couple of questions. You talk about the set temperature over shooting? doesn't the room thermostat control this without you having to manually switch off? Also is there any control of the temperature of the warm air emitted from the units or is it only the fan speed that's adjustable? If the air temperature is fixed typically what is this? Thanks
You can't control the temperature of the air coming out of the units directly, only the fan speed, although by setting a lower room temperature the air coming out of the units does tend to be lower too, from about 40 at its maximum, down to 30 or so when not much heat is required. When I say overshooting I mean that if I set the temperature to 19 the room ends up at 20 or 21, for example. The units themselves have an internal thermistor, they don't have an external one (or at least ours don't, you can get ones with external thermistors), I use independent thermometers to see what the room temperatures are. The issue with multi-split systems is that the rooms can all be different temperatures, so if only one of them requires heat the external unit will be on, and so a trickle of heat is always getting provided to the other indoor units connected to the same outdoor unit, even if they are off themselves. Only if all the indoor units connected to a single outdoor unit are at or above temperature then that's when the outdoor unit turns off, or starts cycling.
@TimAndKatsGreenWalk Thanks Tim. So the control for the room temperature is within the unit which is usually at a high position close to ceiling? In that case it will be influenced by the air temperature at that point being at a higher temperature than where we sit or stand. Correct me if I'm wrong that doesn't appear sensible one would have to work out some sort of offset factor? Have I completely misunderstood 😕
@@jonnythompson2711 yup, that's pretty much it. You can get external thermistors we just don't have them for ours. Apparently you can remove the internal ones and site them away from the units, which can help. There a lot of other factors that can affect it like the size of the room etc. and some overshoot more than others, some don't overshoot at all in fact. It's also constantly pulling air in and blowing it out, bear in mind, so the air gets pretty well mixed in the room, although I'm sure it's not totally uniform. Generally it's not an issue as you just set the temperature controls to whatever results in the intended room temperature, so we set to 19 if we want 20-21, say, and that's fine. It's a lot easier than trying to tinker with radiator valves, that's for sure!
@TimAndKatsGreenWalk Thanks for explaining that and I'm sure one could adjust accordingly. Just one last thing you say there's no direct control on the temperature of the warm air being emitted? If that's the case is this one thing that a2a can't do and a2w can? I fully appreciate that it's not at all efficient but having that ability to raise the flow temperature if absolutely necessary could be reassuring.
Actually, out of interest I just used my IR thermometer to measure the temperature of the floor and ceiling in the office where I'm sat and it's 20.8 on the floor and 21.8 on the ceiling.
I do similar with our A2W system, but only on the lower floor, which has under-floor heating (eg a huge emitter) and it's working very well. What I'd like to try and work out is, although it's definitely cheaper to thermally charge the house at 7p/kWh versus 26.72p/kWh, I'd be curious to see the COP differential between say, running the ASHP at midnight vs midday (when, typically, it would be a few degrees warmer outside...)...do you have this data?
I don't have that data, sadly, no. It is a very interesting question though, and one I'd like to understand more about. There definitely will be a small difference in COP but I don't think it'd be enough to make the overnight heating strategy any less beneficial.
@@TimAndKatsGreenWalk agreed, I cannot concieve of it ever working out more expensive, seeing as the cost per unit is nearly a quarter of the price! I just want the stats!
@@justinjoanknecht3475 I can relate.
It’s not THE most financially viable option, but I strongly advocate for getting batteries to cover your highest average daily usage without factoring in panels. Ignoring the 5-10 days a year it’s obscenely cold etc.
Being independent and power cut proof, at least in my mind, was worth the extra cost.
April - October, where solar is reasonably reliable, you can set up an export schedule to abuse the import tariff and offset the cost.
I think we've got just about the sweet spot of battery capacity for our needs, balancing battery cost with savings. I did a whole video about it, in fact: th-cam.com/video/_qysulne5g0/w-d-xo.html
That's not to say I wouldn't love more capacity, but at the moment I can't really justify it. If battery prices halved then I would absolutely get another 5-10 kWh.