I've made an addition to the spreadsheet to include savings from removing the gas standing charge. I've also assumed half the savings can be associated with the iHP while the other half are associated with the replacement heating system (e.g. A2A heat pump) for fairness, but there is a cell you can change to vary that proportion. It shaves off a few years from the payback, for sure.
That’s a positive then. I never had a gas charge due to not having gas in the remote Scottish highlands but I am now completely off oil and all electric now 😃
Excellent work as usual Tim, the detail you put into these spreadsheets is really commendable, as is making them available for all of us to make better informed decisions relating to our own situations. Bravo.
Thank you, and no problem. I think I might have missed a couple of factors that might be worth considering so I'll probably do a quick update to this video soon. The spreadsheet has already been updated.
Another outstanding presentation. With anything relating to 'renewable energy', there is a preoccupation with ROI. Sometimes it's about lifestyle and personal choice, as with many other things in life. Love the spreadsheet, clear and well thought out. Cheers.
Thank you. Yes, I agree, I'd rather these sort of videos weren't necessary but I know if I didn't do them people would be asking about the payback all the time! I'll be covering a lot more about the iHP soon, in particular all the benefits you get over a normal cylinder, such as the level of control, and the app/web portal, which is all super helpful.
Been waiting for this one also! Thanks for all the effort Tim. Think this was picked up in another comment but I agree if you add in the cost of replacing the boiler then it puts a stronger argument towards an iHP solution. We are mostly covered by A2A in our house now, and our storage combi would be £4-5k to replace at the end of its life. Definitely lining up to drop the boiler and move to an iHP or similar in a few years once we have the last pieces of A2A in place.
Yes, I think I should include that in the calculation so I've updated the spreadsheet accordingly and will do a quick update video next week. It does make quite a difference. Great to hear your A2A is working well for you. I've got to say it was the best decision we made when we decided to go that route.
@@TimAndKatsGreenWalk great, thank you! Good that the A2A is working out at your end also. Only downside I’ve seen is the power consumption seems to increase quite a lot when it’s below freezing in UK, but rest of the time it’s relatively cheap to run. About to start a rip out of the bathroom also, and will go electric on the towel radiators with a Shelly smart relay :)
Great analysis Tim, thanks for your work to pull that all together. Sorry if I missed you mentioning it, but I think it’s possibly important to the people looking at pay back as a motivator that the heat pump is only guaranteed for a short time, whereas the cylinder is much longer. So there is a possible high cost to replacing the heat pump. This, and the higher risk of it going wrong due to complex moving parts is why I decided to just go immersion at off peak (likely green power) times despite the lower efficiency. In the grand scheme of things my water consumption and therefore environmental impact is low. It would also be interesting to know the environmental impact of the heat pump manufacturing vs an immersion heater.
You're right, there is the possibility you'd need to replace the heat pump sooner than an immersion, say. I didn't cover that, no. The warranty is 5 years for the heat pump part of the iHP but it should last longer than that with any luck. As for the environmental cost of the manufacturing I did find an analysis on the Mixergy website where they show the carbon footprint of the manufacture of the heat pump and cylinder and compared to a regular cylinder. I stumbled on it while researching the iHP but not sure if I could find it again now, but if I recall correctly the carbon payback was only a couple of years, which reassured me that it was worth doing on an environmental basis. Using an immersion overnight is also way better than using gas, so I'd say your choice was also totally valid and it's what we've been doing for the past two years.
Thanks Tim, yes 5 years is what I recall. The benefit of the iHP being that it can be replaced and you retain the cylinder, unlike some other heat pump cylinders which have a single warranty for the heat pump and cylinder as they are integrally linked. Given some of the payback periods you mention stretching into decades, then it seems likely a new heat pump might be needed in that time and should be factored in by those that care about payback. Mixergy couldn’t tell me at the time I looked into it what a replacement heat pump unit would cost. Good to hear some form of LCA data is available. I’ll see if I can find it. A couple of years carbon payback isn’t much but perhaps an important factor for some vs other options. The stainless steel cylinder means that component should last a very long time indeed, and be more likely to be recycled at the end of life. Thanks again. Excellent video as always!
Excellent article! The gas calculations look quite high compared to our actual figures though. Our daily usage (2 of us) is roughly the same as yours, apart from a Sunday when we indulge in a large bath. In an average month* we use around 89.6kWh for gas hot water, circa 3kWh per day. If we removed the indulgence of the bath it would equate to 2.16kWh per day. We achieve a genuine 91.5% net efficiency on our gas boiler, which helps slightly, we also use a 250L cylinder designed for a heat pump (so a big coil), which probably helps more and have a slightly lower hot water temp set (47ºC) with a tweaked hysteresis. Still, even with the unusually efficient system we have there is still quite a delta from the calculations above. * As an aside, with our old and inefficient gas storage combi boiler we used an average of 900kWh for monthly hot water - it goes to show how bad some real-world gas figures can be. Ripping it out and starting again with the best that Vaillant and a Heat Geek could provide dropped our like-for-like usage by an order of magnitude. With the system occasionally skipping a daily recharge every so often it confuses the Octopus Tracker billing system - it assumes the gas meter has failed and averages it out. It also means our gas bill is now dominated by the daily 27.47p standing charge.
Thanks! Although I'm not sure what you mean by the calculation looking high compared to your usage. I put in the "fraction of cylinder used" as a way for you to change the calculation to better match your actual usage. It sounds like you use less than 50% of the cylinder each day so you'd need to change the value in one of those cells. The gas calculation matches what we used to use pretty closely, so I reckon you're using less hot water than us. The calculation is based on actual physics so it's just a matter of using the appropriate input parameters. If you use less gas then my calculation suggests it means your input parameters aren't correct (note that I use 15 deg for the average input water temperature, it'll be 20 in the Summer and 10 in the Winter so use whatever is appropriate for the time of year). It's super impressive you were able to drop your usage by a factor of 10, that's incredible.
A very timely video for me as we're currently specifying the heating and cooling for our self build passive house. We were given an indication of £7-7.5k installed for a Dimplex Edel (which is a cheaper unit than the Mixergy), so a massive install cost fsctored in. I need to speak with them to understand why as I don't mind a long(ish) payback period over an immersion, but that would be crazy. Thanks for the in depth video!
Wow, that does sound a lot for an Edel install. I'm glad this video could help give you a comparison. In your situation I guess the payback could be considered a fair bit quicker as you'd not need a gas boiler in the first place, so that equivalent cost could be offset against the Edel and heating/cooling system (although I guess you don't need much heating for a passive house!). Good luck with the project, that's something we'd like to do one day.
@@TimAndKatsGreenWalk we're very lucky to be able to attempt a self build. Our heating & cooling is going to be A2A via our MVHR system (Zhender Comfoclime). It's a low output system, but that is all we should need. My current comparison is £2-2.5k on a cylinder + immersion vs. £7-7.5k on an Edel, but I think I need to find another quote for the Edel!
It occurred to me, does the Edel install cost include all the hot water pipes as well? Although I guess if you're comparing against a cylinder with immersion then that would include those pipes too. Hmm, it is curious.
We have had a mixergy installed for almost 2 years and our key learning has been it is cheaper to run and we also have hot water available. We have yet to run the tank out of hot water.
That's good to hear. The main benefit of the standard Mixergy cylinder is the reduced standing losses, assuming you don't need to heat your whole cylinder up all the way. The iHP works a little differently in that you always fully heat it up, as that's the way to get the most efficiency out of the heat pump. Still, in either case it leads to lower energy use, which is what we're all after!
Very detailed - thanks Tim. I think gas is only going up in price in the long run. Gas is being used up quicker than new gas is being generated, and it will have be transported longer distances. The Social Cost of Carbon will only increase as well, and that should ideally be added on to the cost of gas. In the short run the cost would go down if, for instance, the Ukraine war ended.
Yes, indeed, if the price of gas rises the payback of this sort of thing will become shorter, of course. I'm hoping that the current subsidies given to gas for being "green" will get moved over to electricity now that the grid is greener, on average, than gas.
No problem. I think having an idea of possible options well ahead of time is never a bad thing, even if you don't plan on doing anything with that information for a while.
Very interesting, thanks. I’m hoping to get an ihp this year, if I can find an installer (that’s the hard bit). I did look into the SAHP thing, but it seems too good to be true. I don’t see how a passive device can pull in enough energy from the environment.
Interesting, I hadn't heard of SAHP before. I guess it could work if you have a large enough panel, but then you'd probably be better off using the roof space for solar PV. By the way, I did a follow-up to this video covering another scenario that I thought was worth mentioning.
Hi Tim, Many thanks for this video ~ IMHO a solar diversion controller using excess solar PV generation "may" be a better option into an immersion heater, pre heating water to a combi might mean that you could switch off the gas boiler from April through to October and still get all the hot water you needed. Something for others to consider if they have gas. KR AndyT.
Solar divert is an odd one as it totally depends on the level of export tariff you can get. At the moment export tariffs are very high, so you're better off exporting excess solar to the grid than using it for heating hot water, or charging an EV, for example. And then doing your water heating/EV charging at cheaper overnight rates (15 p/kWh export rate vs. 7 p/kWh import rate for Intelligent Octopus Go, for example). But should export rates drop (which they might well do) then solar divert does become a more valuable thing to do, for sure. Just not at the moment, in my opinion.
Tim Will you do the cost saving comparison calculation using evacuated tubes for heating water with existing cylinder and the solar panel diversion for resistive immersion calculation also.
A factor in lifetime ownership calculations is servicing/repair costs. A heat pump is much more complex than an immersion element, is more likely to go wrong, and when it does go wrong it is going to be more expensive to repair. I use a - very arbitrary! - sum of £50 p.a. as the heat pump cylinder's average service/repair cost above and beyond a direct immersion cylinder's in a 15-year lifetime cost analysis. As you say, a combined heat pump cylinder installation does theoretically qualify for the VENSAV zero-rating of VAT (on purchase, ancillary and labour costs). As the consumer cannot claim-back VAT already paid on such an installation, you have to find an installer willing to quote for a VAT-free installation under this scheme. They seem to be rare (non-existent?) - so it would be interesting to know if any of your viewers have found such an installer.
Yes, I would hope these could be installed VAT free, it seems only fair! And I'd probably agree with your £50 p.a. extra maintenance cost, that sounds about right to me.
I did a comparison on my water cylinder of heating it through gas and then through immersion. The results for a tank came out at 12Kwh via gas and 9Kwh via immersion. I believe that taking this efficiency increase into account would change your outcome. Did you do something similar when opting previously to heat via immersion over gas?
You'll see that I include an efficiency for gas boilers (set to 85% in my spreadsheet by default but it can be changed) and immersion heaters (set to 100% by default), so that is already accounted for. In your example the gas boiler efficiency would be 75% or a CoP of 0.75. We found a similar improvement by going from gas to immersion as shown in this very early video on the channel: ruclips.net/video/890C2nSjetg/видео.html We had our gas disconnected and boiler removed, so we didn't have much choice but to use the immersion, really!
Great spreadsheet and video again. Might be one for the next video, but if you were doing it again, would you go for a normal heat pump? Or a normal heat pump and a few air con cooling only units? Or would you still go air to air and iHP.
We'd definitely still go A2A just because of the cooling. But if there was a viable option that did hot water too that would have been good. As it stands there weren't any such systems when we got our A2A installed but some are starting to appear on the UK market now, so I'd do more research into that option if I was doing it now.
Is solar thermal water heating very hard in the UK? I assume so since it's so cloudy but the newer selective solar collectors have really changed the game. Here in Greece we have "free" DHW from the sun for like 85% of the year. Total cost after installation for a 150 liter system around €700 - €1000 after install.
It's certainly an option in the UK, although given how cheap solar PV is now it's becoming less popular and less cost effective relative to PV installs.
Solar thermal is harder in the UK because we have to worry about water freezing if it's outside our insulation. Instead of a simple thermo-syphon system we have to pump glycol around. That makes everything more expensive. It's never really been economical, and now it's competing for roof space with PV.
the maintenance on these systems as they have to survive freezing temperatures make them uneconomical, they can still work in commercial applications, but PV is getting so cheap I'm not sure its going to stay that way.
@@TimAndKatsGreenWalkyes I've been there done that, solar tubes work very well but they only produce hot water! PV panels you can do what you want. Also there is quite a high maintenance cost with the tubes, none with pv. I stripped my tubes off in 2015, replaced with panels and now also get a FIT as well as free electricity
I mention that in the spreadsheet. You also have to service unvented cylinders every year, apparently (I honestly don't know how many people actually do this), so the servicing cost is similar.
@@TimAndKatsGreenWalk I didn’t see it on the video which is why I mentioned it. Still on gas with an old copper cylinder, can’t say it’s ever been serviced though the boiler itself is. It’s probably nasty in there 🤢
@@sentyuk5322 yeah, I didn't mention it in the video, it was already getting kinda long! I was actually quite surprised to find it was a requirement for cylinder warranties but I don't think I've ever had one serviced before.
@@sentyuk5322 thanks, I appreciate that. I never thought making spreadsheets on RUclips would ever be a thing people would want to see, but there you go!
Im waiting for someone to actually revolutionise home heating so I can heat my water from the heat I don't want in my room's this time of year, until then its open therm and closed-loop control gas heating for me.
I'm in the US and my HVAC system uses forced air, ducts everywhere, so I could maybe do this. I think a better idea is to pull hot air from a refrigerator or a hot attic.
There is solution for you. Exhaust heat pump. Like HP Mixergy but connected to the ventilation ducting where you "feed" your HP by exchanging warm air in the rooms where required (loft, south facing rooms, conservatory etc) for fresh one from outside. Like an Aircon but hot water is being produced at the same time and air is being replaced (aircon generally doesn't do that.
if you got rid of gas completely then you wouldnt need to pay the gas supply cost over the year so is that not another saving ?
That is true.
I've made an addition to the spreadsheet to include savings from removing the gas standing charge. I've also assumed half the savings can be associated with the iHP while the other half are associated with the replacement heating system (e.g. A2A heat pump) for fairness, but there is a cell you can change to vary that proportion. It shaves off a few years from the payback, for sure.
That’s a positive then. I never had a gas charge due to not having gas in the remote Scottish highlands but I am now completely off oil and all electric now 😃
@@bobbazley5376 it's a good feeling, isn't it?
Indeed it is but anything to reduce costs is good
Excellent work as usual Tim, the detail you put into these spreadsheets is really commendable, as is making them available for all of us to make better informed decisions relating to our own situations. Bravo.
Thank you, and no problem. I think I might have missed a couple of factors that might be worth considering so I'll probably do a quick update to this video soon. The spreadsheet has already been updated.
Another outstanding presentation. With anything relating to 'renewable energy', there is a preoccupation with ROI. Sometimes it's about lifestyle and personal choice, as with many other things in life. Love the spreadsheet, clear and well thought out. Cheers.
Thank you. Yes, I agree, I'd rather these sort of videos weren't necessary but I know if I didn't do them people would be asking about the payback all the time! I'll be covering a lot more about the iHP soon, in particular all the benefits you get over a normal cylinder, such as the level of control, and the app/web portal, which is all super helpful.
Been waiting for this one also! Thanks for all the effort Tim. Think this was picked up in another comment but I agree if you add in the cost of replacing the boiler then it puts a stronger argument towards an iHP solution.
We are mostly covered by A2A in our house now, and our storage combi would be £4-5k to replace at the end of its life.
Definitely lining up to drop the boiler and move to an iHP or similar in a few years once we have the last pieces of A2A in place.
Yes, I think I should include that in the calculation so I've updated the spreadsheet accordingly and will do a quick update video next week. It does make quite a difference. Great to hear your A2A is working well for you. I've got to say it was the best decision we made when we decided to go that route.
@@TimAndKatsGreenWalk great, thank you! Good that the A2A is working out at your end also. Only downside I’ve seen is the power consumption seems to increase quite a lot when it’s below freezing in UK, but rest of the time it’s relatively cheap to run.
About to start a rip out of the bathroom also, and will go electric on the towel radiators with a Shelly smart relay :)
@@chriswright2552 nice. I'm rapidly running out of things to do now, so not sure what I'll cover on the channel after the iHP videos are done!
Great analysis Tim, thanks for your work to pull that all together.
Sorry if I missed you mentioning it, but I think it’s possibly important to the people looking at pay back as a motivator that the heat pump is only guaranteed for a short time, whereas the cylinder is much longer. So there is a possible high cost to replacing the heat pump.
This, and the higher risk of it going wrong due to complex moving parts is why I decided to just go immersion at off peak (likely green power) times despite the lower efficiency. In the grand scheme of things my water consumption and therefore environmental impact is low. It would also be interesting to know the environmental impact of the heat pump manufacturing vs an immersion heater.
You're right, there is the possibility you'd need to replace the heat pump sooner than an immersion, say. I didn't cover that, no. The warranty is 5 years for the heat pump part of the iHP but it should last longer than that with any luck. As for the environmental cost of the manufacturing I did find an analysis on the Mixergy website where they show the carbon footprint of the manufacture of the heat pump and cylinder and compared to a regular cylinder. I stumbled on it while researching the iHP but not sure if I could find it again now, but if I recall correctly the carbon payback was only a couple of years, which reassured me that it was worth doing on an environmental basis. Using an immersion overnight is also way better than using gas, so I'd say your choice was also totally valid and it's what we've been doing for the past two years.
Thanks Tim, yes 5 years is what I recall. The benefit of the iHP being that it can be replaced and you retain the cylinder, unlike some other heat pump cylinders which have a single warranty for the heat pump and cylinder as they are integrally linked.
Given some of the payback periods you mention stretching into decades, then it seems likely a new heat pump might be needed in that time and should be factored in by those that care about payback.
Mixergy couldn’t tell me at the time I looked into it what a replacement heat pump unit would cost.
Good to hear some form of LCA data is available. I’ll see if I can find it. A couple of years carbon payback isn’t much but perhaps an important factor for some vs other options. The stainless steel cylinder means that component should last a very long time indeed, and be more likely to be recycled at the end of life.
Thanks again. Excellent video as always!
Excellent article!
The gas calculations look quite high compared to our actual figures though. Our daily usage (2 of us) is roughly the same as yours, apart from a Sunday when we indulge in a large bath. In an average month* we use around 89.6kWh for gas hot water, circa 3kWh per day. If we removed the indulgence of the bath it would equate to 2.16kWh per day. We achieve a genuine 91.5% net efficiency on our gas boiler, which helps slightly, we also use a 250L cylinder designed for a heat pump (so a big coil), which probably helps more and have a slightly lower hot water temp set (47ºC) with a tweaked hysteresis. Still, even with the unusually efficient system we have there is still quite a delta from the calculations above.
* As an aside, with our old and inefficient gas storage combi boiler we used an average of 900kWh for monthly hot water - it goes to show how bad some real-world gas figures can be. Ripping it out and starting again with the best that Vaillant and a Heat Geek could provide dropped our like-for-like usage by an order of magnitude. With the system occasionally skipping a daily recharge every so often it confuses the Octopus Tracker billing system - it assumes the gas meter has failed and averages it out. It also means our gas bill is now dominated by the daily 27.47p standing charge.
Thanks! Although I'm not sure what you mean by the calculation looking high compared to your usage. I put in the "fraction of cylinder used" as a way for you to change the calculation to better match your actual usage. It sounds like you use less than 50% of the cylinder each day so you'd need to change the value in one of those cells. The gas calculation matches what we used to use pretty closely, so I reckon you're using less hot water than us. The calculation is based on actual physics so it's just a matter of using the appropriate input parameters. If you use less gas then my calculation suggests it means your input parameters aren't correct (note that I use 15 deg for the average input water temperature, it'll be 20 in the Summer and 10 in the Winter so use whatever is appropriate for the time of year). It's super impressive you were able to drop your usage by a factor of 10, that's incredible.
A very timely video for me as we're currently specifying the heating and cooling for our self build passive house. We were given an indication of £7-7.5k installed for a Dimplex Edel (which is a cheaper unit than the Mixergy), so a massive install cost fsctored in. I need to speak with them to understand why as I don't mind a long(ish) payback period over an immersion, but that would be crazy. Thanks for the in depth video!
Wow, that does sound a lot for an Edel install. I'm glad this video could help give you a comparison. In your situation I guess the payback could be considered a fair bit quicker as you'd not need a gas boiler in the first place, so that equivalent cost could be offset against the Edel and heating/cooling system (although I guess you don't need much heating for a passive house!). Good luck with the project, that's something we'd like to do one day.
@@TimAndKatsGreenWalk we're very lucky to be able to attempt a self build. Our heating & cooling is going to be A2A via our MVHR system (Zhender Comfoclime). It's a low output system, but that is all we should need. My current comparison is £2-2.5k on a cylinder + immersion vs. £7-7.5k on an Edel, but I think I need to find another quote for the Edel!
It occurred to me, does the Edel install cost include all the hot water pipes as well? Although I guess if you're comparing against a cylinder with immersion then that would include those pipes too. Hmm, it is curious.
Very well explained Tim thank you 👍👍👍
No problem
Interesting, the last time I used specific heat capacity was during O grade yes O grade physics . Thanks again
Gotta love a bit of physics.
1st here, good to see the update! How many years? wow
Well, it depends where gas prices go, really. If energy prices rise the payback time will fall a fair bit.
Good to see how different option such as the ihp cost to run.
Indeed. Obviously these are theoretical values, so should be taken with a pinch of salt, but should form a reasonable starting point.
We have had a mixergy installed for almost 2 years and our key learning has been it is cheaper to run and we also have hot water available. We have yet to run the tank out of hot water.
That's good to hear. The main benefit of the standard Mixergy cylinder is the reduced standing losses, assuming you don't need to heat your whole cylinder up all the way. The iHP works a little differently in that you always fully heat it up, as that's the way to get the most efficiency out of the heat pump. Still, in either case it leads to lower energy use, which is what we're all after!
Very detailed - thanks Tim.
I think gas is only going up in price in the long run. Gas is being used up quicker than new gas is being generated, and it will have be transported longer distances. The Social Cost of Carbon will only increase as well, and that should ideally be added on to the cost of gas.
In the short run the cost would go down if, for instance, the Ukraine war ended.
Yes, indeed, if the price of gas rises the payback of this sort of thing will become shorter, of course. I'm hoping that the current subsidies given to gas for being "green" will get moved over to electricity now that the grid is greener, on average, than gas.
Thanks for doing the work so we don't have to! Still interesting to some like me with a combi with lots of life left in it.
No problem. I think having an idea of possible options well ahead of time is never a bad thing, even if you don't plan on doing anything with that information for a while.
Very interesting, thanks. I’m hoping to get an ihp this year, if I can find an installer (that’s the hard bit). I did look into the SAHP thing, but it seems too good to be true. I don’t see how a passive device can pull in enough energy from the environment.
Interesting, I hadn't heard of SAHP before. I guess it could work if you have a large enough panel, but then you'd probably be better off using the roof space for solar PV. By the way, I did a follow-up to this video covering another scenario that I thought was worth mentioning.
Hi Tim, Many thanks for this video ~ IMHO a solar diversion controller using excess solar PV generation "may" be a better option into an immersion heater, pre heating water to a combi might mean that you could switch off the gas boiler from April through to October and still get all the hot water you needed. Something for others to consider if they have gas. KR AndyT.
Solar divert is an odd one as it totally depends on the level of export tariff you can get. At the moment export tariffs are very high, so you're better off exporting excess solar to the grid than using it for heating hot water, or charging an EV, for example. And then doing your water heating/EV charging at cheaper overnight rates (15 p/kWh export rate vs. 7 p/kWh import rate for Intelligent Octopus Go, for example). But should export rates drop (which they might well do) then solar divert does become a more valuable thing to do, for sure. Just not at the moment, in my opinion.
On most tariffs you are better off exporting the electricity and using gas for your water heating.
Tim Will you do the cost saving comparison calculation using evacuated tubes for heating water with existing cylinder and the solar panel diversion for resistive immersion calculation also.
No, that video was quite long enough already. The spreadsheet is available for you to do your own comparisons if you wish though.
@@TimAndKatsGreenWalk ahh Tim! . I don't have the time
@@alanc1406 neither do I, sadly! Too many videos to do.
A factor in lifetime ownership calculations is servicing/repair costs. A heat pump is much more complex than an immersion element, is more likely to go wrong, and when it does go wrong it is going to be more expensive to repair. I use a - very arbitrary! - sum of £50 p.a. as the heat pump cylinder's average service/repair cost above and beyond a direct immersion cylinder's in a 15-year lifetime cost analysis.
As you say, a combined heat pump cylinder installation does theoretically qualify for the VENSAV zero-rating of VAT (on purchase, ancillary and labour costs). As the consumer cannot claim-back VAT already paid on such an installation, you have to find an installer willing to quote for a VAT-free installation under this scheme. They seem to be rare (non-existent?) - so it would be interesting to know if any of your viewers have found such an installer.
Yes, I would hope these could be installed VAT free, it seems only fair! And I'd probably agree with your £50 p.a. extra maintenance cost, that sounds about right to me.
I did a comparison on my water cylinder of heating it through gas and then through immersion. The results for a tank came out at 12Kwh via gas and 9Kwh via immersion. I believe that taking this efficiency increase into account would change your outcome. Did you do something similar when opting previously to heat via immersion over gas?
You'll see that I include an efficiency for gas boilers (set to 85% in my spreadsheet by default but it can be changed) and immersion heaters (set to 100% by default), so that is already accounted for. In your example the gas boiler efficiency would be 75% or a CoP of 0.75. We found a similar improvement by going from gas to immersion as shown in this very early video on the channel: ruclips.net/video/890C2nSjetg/видео.html
We had our gas disconnected and boiler removed, so we didn't have much choice but to use the immersion, really!
Great spreadsheet and video again. Might be one for the next video, but if you were doing it again, would you go for a normal heat pump? Or a normal heat pump and a few air con cooling only units? Or would you still go air to air and iHP.
We'd definitely still go A2A just because of the cooling. But if there was a viable option that did hot water too that would have been good. As it stands there weren't any such systems when we got our A2A installed but some are starting to appear on the UK market now, so I'd do more research into that option if I was doing it now.
I have a combi gas boiler and my water heating costs come out at approx £80 a year for a family size of 3 adults
Ok. That's pretty low usage compared to the average. That's about 20L per person per day, the average is about 45L per person per day.
@@TimAndKatsGreenWalk
So sleek telling them they don’t shower enough
😂
@@serraios1989 I'm guessing electric showers.
I think the summary is “too expensive”.
Is there an internal unit which could connect with your outside units and heat the water?
No, sadly not. There are systems that do though (although hard to find in the UK):
ruclips.net/video/9domQlKtbBQ/видео.htmlsi=nDgUJ2nXL7BLj8l4
Is solar thermal water heating very hard in the UK? I assume so since it's so cloudy but the newer selective solar collectors have really changed the game. Here in Greece we have "free" DHW from the sun for like 85% of the year. Total cost after installation for a 150 liter system around €700 - €1000 after install.
It's certainly an option in the UK, although given how cheap solar PV is now it's becoming less popular and less cost effective relative to PV installs.
Solar thermal is harder in the UK because we have to worry about water freezing if it's outside our insulation. Instead of a simple thermo-syphon system we have to pump glycol around. That makes everything more expensive. It's never really been economical, and now it's competing for roof space with PV.
the maintenance on these systems as they have to survive freezing temperatures make them uneconomical, they can still work in commercial applications, but PV is getting so cheap I'm not sure its going to stay that way.
Vacuum tubes for solar hot water, was all the rage a number of years back, surely this would be completely free 6 months a year. ?
It's a lot more expensive than you'd think and given how cheap solar PV is nowadays you're usually better off using the roof space for PV instead.
@@TimAndKatsGreenWalkyes I've been there done that, solar tubes work very well but they only produce hot water! PV panels you can do what you want. Also there is quite a high maintenance cost with the tubes, none with pv. I stripped my tubes off in 2015, replaced with panels and now also get a FIT as well as free electricity
Doesn’t the ihp tank need servicing each year or so, that would be another expense :(
I mention that in the spreadsheet. You also have to service unvented cylinders every year, apparently (I honestly don't know how many people actually do this), so the servicing cost is similar.
@@TimAndKatsGreenWalk I didn’t see it on the video which is why I mentioned it.
Still on gas with an old copper cylinder, can’t say it’s ever been serviced though the boiler itself is. It’s probably nasty in there 🤢
@@sentyuk5322 yeah, I didn't mention it in the video, it was already getting kinda long! I was actually quite surprised to find it was a requirement for cylinder warranties but I don't think I've ever had one serviced before.
@@TimAndKatsGreenWalk keep up the great work Tim, I love all the analysis you do on these things 👍
@@sentyuk5322 thanks, I appreciate that. I never thought making spreadsheets on RUclips would ever be a thing people would want to see, but there you go!
Im waiting for someone to actually revolutionise home heating so I can heat my water from the heat I don't want in my room's this time of year, until then its open therm and closed-loop control gas heating for me.
I'm in the US and my HVAC system uses forced air, ducts everywhere, so I could maybe do this. I think a better idea is to pull hot air from a refrigerator or a hot attic.
You can do that with some systems although the extra complexity and cost probably isn't worth it.
There is solution for you. Exhaust heat pump. Like HP Mixergy but connected to the ventilation ducting where you "feed" your HP by exchanging warm air in the rooms where required (loft, south facing rooms, conservatory etc) for fresh one from outside.
Like an Aircon but hot water is being produced at the same time and air is being replaced (aircon generally doesn't do that.