Happy new year! Good performance from the mixergy cylinder. Our 250lt megaflo and system gas boiler supplied for 5 days four adults and four teenage girls. Usually we had the two shower rooms running at the same time and it was impossible to empty the cylinder (setting was continuously on). I recon we used at least 25kwh of gas per day for the hot water.
Thankfully we didn't need that much hot water, I suspect we would have struggled under that load. Although we only used about 3.4 kWh of electricity each day to heat the cylinder. Probably equivalent to about 10 kWh of gas, give or take.
Tim, a most interesting topic and one I'd been thinking about. We're on the road to replacing our LPG boiler but to use less gas (there's no price cap on LPG) we heat our hot water exclusively with our 200 ltr tanks immersion via its myenergi eddi during the intelligent octopus period and an average 4.5 kWh per night that's less than £120 pa or < £10 per month, very happy with that. We don't solar divert since we started exporting at 15p. This works brilliantly for two but come Christmas with 6-9 predominantly younger people in the house, cold showers have occurred. So this year I've allowed gas to do it's thing for two days. It's good to see that a heat pump can cope in such situations and the boost characteristics of the mixergy are interesting. We'll install our A2W HP with the required HW tank replacement but note to self, make sure we can use the immersion in an emergency. Again, a very interesting topic with an excellent level of detail, keep it up and Happy New Year.
Thanks! You should find with a regular A2W system that your water cylinder should reheat a fair bit faster than our iHP as the heat pump is more powerful. Maybe 1-2 hrs rather than 4-5 for us.
Happy new year. Been running a MixErgy 210l (none heat pump) with a Ecodan heat pump for a year and a mixergy tank for 2 years. We let the software handle the levels of the tank and we have yet to run the tank out of hot water. We mainly have baths running, which will of course run through more water than a shower. We occasionally boast the tank but we have figured out it normally not needed at all. We still find how the tank works is impressive and the fact we always have hot water mean one less thing to worry any more. We have find the best combo is solar + battery with a mixergy and let the software look after the tank levels. Assuming the battery is big enough, any boasts would be handled by the battery, assuming you need any boasts ! The solar diverter isn't that helpful in our experience.
Generally we leave the cylinder to it, we only needed to do a bit of active management on these two days because we had so many more people in the house than we usually do. Otherwise we're pretty hands-off with the iHP. The boosting we had to do on 25th and 26th did actually come entirely from the battery so it all worked out pretty well in the end.
I had an 80lt mini store fitted with the heat pump. This gives a couple of showers. As it only takes about 15 mins to recharge I reckon you could have people showering and drying one after each other.
Happy New Year. You mentioned rainshower heads, you could consider fitting an aerator to these (if not already aerating), or using the isolation valve to adjust flow rate. If you search for ‘AECB Water standards’ you should find free guidance on design of hot water systems to prioritise energy efficiency, and also reduce consumption at the same time. You can test flow rates (l/min) by putting a bucket under a shower with say a 10L line marked, then turn it on and time how long it takes to reach the line.
We have actually done the bucket test and these showers use quite a bit more than a normal head. It is quite nice, mind, so I'm not in a hurry to change them. I tend to just not turn them on all the way so that they use a bit less.
@ You could perhaps consider trying an aerating fitting as they are usually a few quid and still ‘feel’ nice with the tiny bubbles! We have one in our rainshower which runs at 6 l/min on full.
If you had the immersion on, it'd probably only heat from the bottom or middle, so it wouldn't be usable straight away. Best use for the immersion would be to carry on heating upto 90c in the off peak, but if it takes over 5hrs to get to 100%, you could only get a cost benefit it on agile or intelligent go. Great advantage of having the iHP as a separate unit was that you didn't loose any house heating whilst heating the water.
Yes, that's actually a very good point I didn't cover in the video; if we'd had a normal cylinder powered by an A2W heat pump system the space heating would have had to pause while the cylinder got reheated. Although, as it happens, we actually needed almost no space heating on Christmas or Boxing Day as the higher number of people in the house, plus all the cooking meant the house stayed pretty warm without it, amazingly.
Happy New Year Tim! A very interesting video and answers a question I'd been mulling over about how the Mixergy would cope. I'm wondering why you wouldn't set the overnight heating to start a little later, to coincide with the end of the Octopus overnight cheaper tarrif, meaning less effect due to the natural decline in temp with time? The beauty of the heat pump is being able to reheat the water during the day with much less power use than just using immersion.
Generally I have no idea ahead of time how long the reheat will take, so rather than risk it going into the day rate (and thus using battery that I would rather save for the space heating) I start at 00:30 so that it's more than likely finished before 05:30. Sometimes when it's really cold it does take longer than 5 hours, so starting as soon as the off-peak period starts is the best overall strategy. The temperature decline is really very slow, so it's still plenty hot enough by the end of the day even if it's finished heating by 04:00, say.
Happy new year to you. I know you have this working to your liking and it does manage you well but if you had your time again would you do things differently? You have separate air to air and a separate hot water heater. Also I think you have electric towel rails. Would an all in one air to water heat pump doing the whole house and water be better? I have neither so genuinely interested.
It's an excellent question. As it happens I'd do more or less the same for our house as we have such huge windows that we really do need the cooling in the summer, so A2A was the sensible option for us. There are now a few systems that do A2A plus hot water (and even a Samsung system that does A2A, A2W and DHW all in one, which is amazing) , but they are still few and far between so getting hold of such a system back then was basically impossible and still pretty hard now. Although if I was doing it again I'd look into that option in more detail to see if it would be viable. As it happens this subject has been on my list of videos to do for a while now so I do intend to cover this in a lot more detail in due course. For most people (without such huge windows) an A2W system is probably the more sensible option, but with summers getting hotter in the UK I can see the demand for A2A increasing over the coming years.
@@TimAndKatsGreenWalk good point about the cooling in the summer. I get that. I wonder about the running cost though. All your systems running separately I wonder if that is more costly than one pump doing it all! Who knows. I’ll look out for your video on a comparison.
@CC_FPV running cost is likely to be similar as the COP of the various parts will be comparable. Install costs for A2A tend to be cheaper than A2W but then the BUS grant isn't currently available for A2A, so that skews it back in favour of A2W. Although combining an iHP with A2A makes install costs comparable to an A2W system (ignoring the BUS), so it gets quite complicated to compare!
Kat is very upset with me that I can now prove that she uses more hot water than me in the shower. I don't think she'd be too impressed if I started sharing that data on TH-cam!
6.84 kWh for both days combined. You can actually see the individual consumption on the charts I showed in the top right corner. Usually it's about 2 kWh per day for just Kat and I at this time of year.
I'm sure there would of been loads of people who had "hot water anxiety"😀 over Xmas.with loads of guests, Even on gas, unless you have a Combi or your boiler is set up for PDHW, lots of people would of run out of hot water. You managed it well with your Mixergy Air to air water heater. I'm surprised as you that you can't boost with the immersion as well! Unless I read it wrong? The figs you showed, even with the immersion on, you are still below 13 amp, and with both working at max, less than my kettle at home.
Yup, currently you can only use the immersion heater if the heat pump is broken. I will be mentioning this to Mixergy to see if there is any way to gain control of the immersion by default, just in case you need it. But you're absolutely right, I suspect there were a lot of other people boosting their hot water tanks, even with gas! At least now I know what to expect for the next time we have that many guests at the same time.
How many litres is your cylinder again? If you had one long continuous hot shower, how long would the hot water last? Or to put it another way, what's the longest hot shower you could have with your system? Thanks.
Crikey, I'm not sure how long it would last but it's a 180L cylinder and we use about 20% for a typical shower, so could get just about five in before it runs out totally. Four to be safe.
@@TimAndKatsGreenWalk I like to have a long, hot shower in the evening (for mental health and sleep reasons), which would be a minimum of 15 minutes, and possibly longer, so I'm wondering if a Mixergy cylinder would last long enough, and therefore would be suitable for my use-case. Thanks.
@prwilson101 it would definitely last 15 mins. You can also get bigger cylinders than ours. If you could work out how many litres per minute your showers usually use then you could find an appropriate sized cylinder, I'm sure.
I'm guessing it's because 2 kW + 1.5 kW is 3.5 kW which is more than the 3.1 kW you can get out of a 13A mains plug or fused spur. I know you can go over 13A for some things, so maybe the reason they don't allow both is because of some UK electrical certification thing? If so, they could split it into two 1.5 kW elements so you can have one and the heat pump, or both immersion elements under the 3 kW limit? I'm guessing that would increase costs though, with an extra welded boss, element, control power circuitry, and programming.
1.5 kW is the heat output of the heat pump not the electrical input. The electrical input maxes out at 0.85 kW, although I've never seen it above 0.55 kW, so combined with a 2 kW immersion it's less than 13A.
@@TimAndKatsGreenWalk Do you have a way to measure the inrush power when starting the compressor in the heat pump? I wonder if it's as simple as avoiding poor customer experience by having an (even small) chance of blowing the 13A fuse on the fused spur due to current spikes, if the immersion was running at the same time. Either way, thanks for sharing your experience. Seems to have been entirely unremarkable, in the best possible way!
@andrewcoles4271 the charts I showed have the heat pump power as a green line, but only measure at 1 minute intervals, so it's possible it's briefly higher than the 0.35 kW it typically starts at.
tankless combi boiler (tankless) would be the only way to get through this, no need to think about hot water, open the tap, hot water there all day long non stop, so much more efficient too as you only burn what you use, as you aint holding hot water in a tank all day
@@TimAndKatsGreenWalk many modern system boilers with high capacity coils can deliver effectively endless hot water for the sort of demand a combi can deal with.
@@edc1569 fair enough. The Heat Geek Mini Store cylinder comes pretty close to operating like a combi-boiler too, with the added benefit of it being heat pump driven.
A bit of a cheek stipulating when guests should have showers “in case we run out of hot water”. No wonder they left it so late! I’d want a reliable on demand system. You probably have fewer guests next Christmas!
So you'd rather just let your guests use all the hot water so that some of them had a cold shower? That seems pretty cruel to me. I never stipulated when guests should shower, only that they spread them out a bit for the benefit of everyone else, which they were all perfectly happy to do. Seems like a perfectly sensible way to ensure everyone had a nice hot shower to me, and I'm sure plenty of gas powered homes with hot water tanks around the country had to do something similar too. I don't much appreciate your judgmental comment, tbh.
HAppy New Year Tim and Kat. Great to hear how well it worked for you and that everyone managed to get a hot shower!
Happy New Year to you too. I've got to admit I was a little worried before Christmas so I'm glad it worked out fine in the end!
Happy new year!
Good performance from the mixergy cylinder.
Our 250lt megaflo and system gas boiler supplied for 5 days four adults and four teenage girls. Usually we had the two shower rooms running at the same time and it was impossible to empty the cylinder (setting was continuously on). I recon we used at least 25kwh of gas per day for the hot water.
Thankfully we didn't need that much hot water, I suspect we would have struggled under that load. Although we only used about 3.4 kWh of electricity each day to heat the cylinder. Probably equivalent to about 10 kWh of gas, give or take.
Tim, a most interesting topic and one I'd been thinking about. We're on the road to replacing our LPG boiler but to use less gas (there's no price cap on LPG) we heat our hot water exclusively with our 200 ltr tanks immersion via its myenergi eddi during the intelligent octopus period and an average 4.5 kWh per night that's less than £120 pa or < £10 per month, very happy with that. We don't solar divert since we started exporting at 15p. This works brilliantly for two but come Christmas with 6-9 predominantly younger people in the house, cold showers have occurred. So this year I've allowed gas to do it's thing for two days.
It's good to see that a heat pump can cope in such situations and the boost characteristics of the mixergy are interesting.
We'll install our A2W HP with the required HW tank replacement but note to self, make sure we can use the immersion in an emergency.
Again, a very interesting topic with an excellent level of detail, keep it up and Happy New Year.
Thanks! You should find with a regular A2W system that your water cylinder should reheat a fair bit faster than our iHP as the heat pump is more powerful. Maybe 1-2 hrs rather than 4-5 for us.
Happy new year. Been running a MixErgy 210l (none heat pump) with a Ecodan heat pump for a year and a mixergy tank for 2 years. We let the software handle the levels of the tank and we have yet to run the tank out of hot water. We mainly have baths running, which will of course run through more water than a shower. We occasionally boast the tank but we have figured out it normally not needed at all. We still find how the tank works is impressive and the fact we always have hot water mean one less thing to worry any more. We have find the best combo is solar + battery with a mixergy and let the software look after the tank levels. Assuming the battery is big enough, any boasts would be handled by the battery, assuming you need any boasts ! The solar diverter isn't that helpful in our experience.
Generally we leave the cylinder to it, we only needed to do a bit of active management on these two days because we had so many more people in the house than we usually do. Otherwise we're pretty hands-off with the iHP. The boosting we had to do on 25th and 26th did actually come entirely from the battery so it all worked out pretty well in the end.
I had an 80lt mini store fitted with the heat pump. This gives a couple of showers. As it only takes about 15 mins to recharge I reckon you could have people showering and drying one after each other.
Very nice. That does look like a nifty piece of kit.
Happy New Year. You mentioned rainshower heads, you could consider fitting an aerator to these (if not already aerating), or using the isolation valve to adjust flow rate. If you search for ‘AECB Water standards’ you should find free guidance on design of hot water systems to prioritise energy efficiency, and also reduce consumption at the same time. You can test flow rates (l/min) by putting a bucket under a shower with say a 10L line marked, then turn it on and time how long it takes to reach the line.
We have actually done the bucket test and these showers use quite a bit more than a normal head. It is quite nice, mind, so I'm not in a hurry to change them. I tend to just not turn them on all the way so that they use a bit less.
@ You could perhaps consider trying an aerating fitting as they are usually a few quid and still ‘feel’ nice with the tiny bubbles! We have one in our rainshower which runs at 6 l/min on full.
@danstewart9323 I'll certainly consider it.
If you had the immersion on, it'd probably only heat from the bottom or middle, so it wouldn't be usable straight away. Best use for the immersion would be to carry on heating upto 90c in the off peak, but if it takes over 5hrs to get to 100%, you could only get a cost benefit it on agile or intelligent go. Great advantage of having the iHP as a separate unit was that you didn't loose any house heating whilst heating the water.
Yes, that's actually a very good point I didn't cover in the video; if we'd had a normal cylinder powered by an A2W heat pump system the space heating would have had to pause while the cylinder got reheated. Although, as it happens, we actually needed almost no space heating on Christmas or Boxing Day as the higher number of people in the house, plus all the cooking meant the house stayed pretty warm without it, amazingly.
Happy New Year Tim! A very interesting video and answers a question I'd been mulling over about how the Mixergy would cope. I'm wondering why you wouldn't set the overnight heating to start a little later, to coincide with the end of the Octopus overnight cheaper tarrif, meaning less effect due to the natural decline in temp with time? The beauty of the heat pump is being able to reheat the water during the day with much less power use than just using immersion.
Generally I have no idea ahead of time how long the reheat will take, so rather than risk it going into the day rate (and thus using battery that I would rather save for the space heating) I start at 00:30 so that it's more than likely finished before 05:30. Sometimes when it's really cold it does take longer than 5 hours, so starting as soon as the off-peak period starts is the best overall strategy. The temperature decline is really very slow, so it's still plenty hot enough by the end of the day even if it's finished heating by 04:00, say.
@@TimAndKatsGreenWalk good to know
Happy new year to you.
I know you have this working to your liking and it does manage you well but if you had your time again would you do things differently?
You have separate air to air and a separate hot water heater. Also I think you have electric towel rails. Would an all in one air to water heat pump doing the whole house and water be better?
I have neither so genuinely interested.
It's an excellent question. As it happens I'd do more or less the same for our house as we have such huge windows that we really do need the cooling in the summer, so A2A was the sensible option for us. There are now a few systems that do A2A plus hot water (and even a Samsung system that does A2A, A2W and DHW all in one, which is amazing) , but they are still few and far between so getting hold of such a system back then was basically impossible and still pretty hard now. Although if I was doing it again I'd look into that option in more detail to see if it would be viable. As it happens this subject has been on my list of videos to do for a while now so I do intend to cover this in a lot more detail in due course. For most people (without such huge windows) an A2W system is probably the more sensible option, but with summers getting hotter in the UK I can see the demand for A2A increasing over the coming years.
@@TimAndKatsGreenWalk good point about the cooling in the summer. I get that.
I wonder about the running cost though. All your systems running separately I wonder if that is more costly than one pump doing it all! Who knows.
I’ll look out for your video on a comparison.
@CC_FPV running cost is likely to be similar as the COP of the various parts will be comparable. Install costs for A2A tend to be cheaper than A2W but then the BUS grant isn't currently available for A2A, so that skews it back in favour of A2W. Although combining an iHP with A2A makes install costs comparable to an A2W system (ignoring the BUS), so it gets quite complicated to compare!
Happy new year, slightly disappointed no spreadsheet on total shower time vs charging time 😂. Only joking lol
Kat is very upset with me that I can now prove that she uses more hot water than me in the shower. I don't think she'd be too impressed if I started sharing that data on TH-cam!
@TimAndKatsGreenWalk 😂
Hi Tim, happy new year. Just out of interest what was you total kwh usage on the mixergy for the 2 days?
6.84 kWh for both days combined. You can actually see the individual consumption on the charts I showed in the top right corner. Usually it's about 2 kWh per day for just Kat and I at this time of year.
Aha that's really good going considering the usage!
Yeah, I was impressed. That was the whole point of getting this cylinder after all, so I'm glad it's working as intended.
I'm sure there would of been loads of people who had "hot water anxiety"😀 over Xmas.with loads of guests, Even on gas, unless you have a Combi or your boiler is set up for PDHW, lots of people would of run out of hot water.
You managed it well with your Mixergy Air to air water heater.
I'm surprised as you that you can't boost with the immersion as well! Unless I read it wrong?
The figs you showed, even with the immersion on, you are still below 13 amp, and with both working at max, less than my kettle at home.
Yup, currently you can only use the immersion heater if the heat pump is broken. I will be mentioning this to Mixergy to see if there is any way to gain control of the immersion by default, just in case you need it. But you're absolutely right, I suspect there were a lot of other people boosting their hot water tanks, even with gas! At least now I know what to expect for the next time we have that many guests at the same time.
How many litres is your cylinder again? If you had one long continuous hot shower, how long would the hot water last? Or to put it another way, what's the longest hot shower you could have with your system? Thanks.
Crikey, I'm not sure how long it would last but it's a 180L cylinder and we use about 20% for a typical shower, so could get just about five in before it runs out totally. Four to be safe.
@@TimAndKatsGreenWalk I like to have a long, hot shower in the evening (for mental health and sleep reasons), which would be a minimum of 15 minutes, and possibly longer, so I'm wondering if a Mixergy cylinder would last long enough, and therefore would be suitable for my use-case. Thanks.
@prwilson101 it would definitely last 15 mins. You can also get bigger cylinders than ours. If you could work out how many litres per minute your showers usually use then you could find an appropriate sized cylinder, I'm sure.
I'm guessing it's because 2 kW + 1.5 kW is 3.5 kW which is more than the 3.1 kW you can get out of a 13A mains plug or fused spur. I know you can go over 13A for some things, so maybe the reason they don't allow both is because of some UK electrical certification thing?
If so, they could split it into two 1.5 kW elements so you can have one and the heat pump, or both immersion elements under the 3 kW limit? I'm guessing that would increase costs though, with an extra welded boss, element, control power circuitry, and programming.
8:30 the max the heat pump will pull is 0.85kW, so total would be 2.85kW, so would be fine to run both on 13A.
1.5 kW is the heat output of the heat pump not the electrical input. The electrical input maxes out at 0.85 kW, although I've never seen it above 0.55 kW, so combined with a 2 kW immersion it's less than 13A.
@@TimAndKatsGreenWalk Do you have a way to measure the inrush power when starting the compressor in the heat pump? I wonder if it's as simple as avoiding poor customer experience by having an (even small) chance of blowing the 13A fuse on the fused spur due to current spikes, if the immersion was running at the same time.
Either way, thanks for sharing your experience. Seems to have been entirely unremarkable, in the best possible way!
@andrewcoles4271 the charts I showed have the heat pump power as a green line, but only measure at 1 minute intervals, so it's possible it's briefly higher than the 0.35 kW it typically starts at.
tankless combi boiler (tankless) would be the only way to get through this, no need to think about hot water, open the tap, hot water there all day long non stop, so much more efficient too as you only burn what you use, as you aint holding hot water in a tank all day
Not as efficient as a heat pump, mind ;) But yes, a combi boiler is the only way to guarantee a continuous supply of on-demand hot water.
@@TimAndKatsGreenWalk many modern system boilers with high capacity coils can deliver effectively endless hot water for the sort of demand a combi can deal with.
@@edc1569 fair enough. The Heat Geek Mini Store cylinder comes pretty close to operating like a combi-boiler too, with the added benefit of it being heat pump driven.
Not more efficient, especially if you're using the hot water within a day or two. A heat pump heated hot water cylinder will always be more efficient.
A bit of a cheek stipulating when guests should have showers “in case we run out of hot water”. No wonder they left it so late! I’d want a reliable on demand system. You probably have fewer guests next Christmas!
So you'd rather just let your guests use all the hot water so that some of them had a cold shower? That seems pretty cruel to me. I never stipulated when guests should shower, only that they spread them out a bit for the benefit of everyone else, which they were all perfectly happy to do. Seems like a perfectly sensible way to ensure everyone had a nice hot shower to me, and I'm sure plenty of gas powered homes with hot water tanks around the country had to do something similar too. I don't much appreciate your judgmental comment, tbh.
guess you've not been invited around many people's homes, I can't imagine why.