Outstanding Video!!!! Well done you. High praise from a retired "Building Services Controls Engineer". Excellent details of the whole process. Will definitely be watching more of your videos, as this is the first I've seen, and may be questioning you in the future, although I think you may have covered everything already!!!!!🤫
A very informative and persuasive account of your experience of living with a heat pump one year on following installation. It's converted me. I'm now going to seek quotes for a heat pump for my house to replace my gas boiler.
Brilliant work gentlemen! This mirrors my experience in just about every way. I also have a 7kW Arotherm plus with microbore which I've documented extensively on my channel. Largest heat pump quote i got was for a 16kW unit!😮
It's difficult to explain how nice and warm our house is with a heat pump. Similar system 7kW Arotherm + with microbore on OEM too! Great video and detail - thanks for sharing.
5kW here and house (with 10mm plastic microbore) has never been toastier nor costing as little to heat, I absolutely love it. The heat is so much more even/pleasant too, I find. And yes, loving the OEM kit too, so much extra info (OEM is the OpenEnergyMonitoring system you use Hugh, to answer your question above).
Thanks James I agree I was persuaded to put 8.5 kw heat pump and I calculated a heat loss under 5KW . Thanks for pointing out other section of open energy monitor with the scatter graph which confirms a 5 kw would have done easily . As per usual very informative cheers Andrew
Good video as always James, when we were on the Cosy tarif we did the hot water in the 1pm slot but. We're now finding the Tracker tarif to be overall cheaper this last year and no stress having to load shift.
@@hughrattray9354 I don't have an up to date scop as we made another change recently (replaced towel rails with more k2s) but today with 8° outdoor and 21.5° indoor we have cop of 4.3
Very interesting regarding your experience on tariffs. Hugh my brother is hte presenter, I am the cameraman and audience. Really appreciate the fact you enjoy the videos.
Love watching your videos James, they were an inspiration for my own 5kw Vaillant install in the summer. My plastic 10mm microbore has been no barrier and the system is working happily since install. Only one issue I disagree with you on, Octopus energy. They used to be good and well recommended but no more. They arranged for my Gas meter to be removed and capped in May, it got removed fine but they are still billing me for the standing charge and estimated usage. I transferred over to E.ON EV tariff (7 hours at 6.9p at night and better solar payments) at the end of July, still no final bill from them. I've emailed several times, called and emailed complaints, each time it takes two days for a reply and promises it'll be fixed. It's not a one off either, my dad transferred electric and gas to a new provider, his transfer worked great and final bill came indicating they'd pay credit directly into account on a particular date. Three weeks later no credit, no helpful support. I think they've expanded too much and struggling.
It is good to hear your microbore system is working well. I think it helps to dispel the myth that you have to rip it all out. Sorry to hear of your bad experience with Octopus. it is also good to see that E.ON are offering good tariffs too
Thanks james for taking the time to provide an update - thorough as always! As you covered previously - worth downloading smart meter data for your current gas boiler as a good way to sanity check your heat loss calcs - not forgetting that most boilers will be running sub 90% efficiency! 7kw ashp should be good for most houses. Potential savings from octapus cosy looks very interesting. 👍
You might struggle to get Octopus to let you have a small heatpump. MCS rules are applied rigidly, and they point blank refused me an 8kw (which can modulate much lower than the 9kW monobloc). My calcs based on gas use the said we only needed 7kw max (90s detached 4-bed, fairly well insulated, also microbore). Only cost me £1750 after the grant though 😊.
Totally agree - I cannot see why historical gas usage wouldn't be the primary guide to how big a ASHP is required, especially if you were able to run the gas boiler with a nice low flow temp over a couple of winter months.
Another very informative video. Just wanted to point out that the calculation for the cosy tariff assumes 105% use 75+25+5 ! So the assumption could work a little cheaper still.
Brilliant video with lots of well thought out data. Really good to hear you talking about systems being oversized as it's a common theme I've seen on other owners videos. Realistically if the temperature is lower than design temperature for a day or two it will just cost a bit more to run. This laziness of installers will only hinder the uptake as the units are physically bigger and cost hundreds of pounds more.
I agree. I don't think the heat loss calculations are taken seriously enough. If they are done right they ensure you get the right sized heat pump. I suspect over sized gas boilers have been fitted for years too.
@@DomSta03 That is true but there are a few things, particularly air changes per hour, that have a massive impact and are largely guesses so I think you can influence the result by questioning the figure used. I also got the impression that many installers just guessed the heat loss by looking at the property and then followed with the heat loss calculations
@@hughrattray9354 Oversizing is guaranteed by the MCS regulations - heat loss calculations are one small part of the picture. They take no account of so many other factors like solar gain, household appliances, people or pets. The biggie is air changes per hour based on the date the house was built - how fucking accurate is that?
Thanks, James for sharing your experience with heat pumps. I see you also have a Powerwall battery. Does it run the heat pump when you come off the overnight cheap rate at 05:30? I'd imagine doing so would bring your energy bills down even further than shown in the video.
Yes the Powerwall runs the whole house and it is topped up by any solar there is. Last winter the Powerwall covered most days and I only had to draw from the grid on cold and cloudy days.
heat punk is a fantastic free heat loss calculation program if you do a separate video on the subject. it allows you to play with the fabric of the building and see the gains you would make replacing a window or adding insulation.
Coincidentally, I spent a couple of hours yesterday putting a plan into Heat Punk and comparing it with my own calculation. I am very impressed and will feature it in any video on heat loss calculations.
Great video, very interesting! Microbore with no buffer tank and no glycol - see, it can be done! Even more evidence that installers are overdoing it to (1) reduce their risks by using bigger HPs, buffers, etc, and (2) gain extra profit for kit and associated labour, both at the expense of the customer! Spot on with the analogy of a too big car engine. I would also add that HPs modulate down but the bigger they are the less they can modulate down - so when you only need a low kW output a big HP will keep cycling which is less efficient. Poor performance is also because of having buffers/LLHs when not needed, especially when combined with a second circuit pump which is "fighting" against the HP's own pump. Design is critical with a HP solution. I always say that if you get it wrong with a gas boiler you make a 10% loss in efficiency that nobody will notice but if you get it wrong with a HP you could easily lose 200% efficiency which could mean a cold house! With "reduced occupancy", are you using TRVs to turn off the unused rooms? Amid some saying to run "open circuit" and not use TRVs (which I am not clear on why), I too have 2-3 rooms I sometimes don't want to heat for days or weeks on end. Is doing this and not having a buffer/LLH mean too much stress on the HP potentially reducing its longevity? On the point of the grant being generous, I agree it is but I also think that installers are somewhat taking advantage (as they always do) so that much of the grant is consumed/lost. Plus the prices may come down as the installations go up due to economies of scale and knowledge gained to optimise installations. Still, it is a good time to get one though.
I am not sure if this reply was uploaded before so I am trying again. Great comments. I think many installers never look back to see how their installs perform so they err on the side of playing it very safe. I was told by my friend’s installer that many people in the industry were looking at my first video (10 months ago) on my installation. It was creating a lot of discussion and, perhaps, making them think again. Bigger heat pumps modulate more and they also require higher flow rates which would have been more of a challenge for my system. I agree with your comment about the design stage and a crucial part of that is a proper heat loss calculation which many installers don’t seem to do. You are correct about the heat loss with reduced occupancy being 3.7Kw. That is the more common state but it is good to be able to accommodate the family when needed. I have a Honeywell Evohome system controlling the TRVs so all rooms are frost protected and can be controlled separately. All the living rooms have the radiators continually open so that is at least 7 radiators. I also have a 25ltr volumiser tank. This allows plenty of flow for the 7Kw and the cycle time is long so I don’t believe this causes any stress on the HP. I think the number of HP being installed has picked up a lot so the installers are able to charge high prices. Unfortunately this is not helping the reputation of heat pumps. If you google heat pump prices they are not as expensive as you would think and they have no VAT. Do you have a heat pump? Or are you planning to get one.
@@hughrattray9354 Thank you , I live alone in a small three bedroom terraced house and only use a couple of rooms in the house , so I have been arguing with myself of which way to go = air to water or air to air , so I’m totally confused in which one would suit me best .
@@hughrattray9354 If the radiators have to be bigger as an example is that also disruptive, I live alone so it really makes no difference of the upheaval, but in my situation heating areas in the house I don’t really use seems pointless, I don’t know myself about the heat pump scenarios, but I keep asking myself surely air to air for me seems correct, of course I could be wrong very hard to get an opinion from an independent person , obviously any installer is thinking about which is best for themselves.
@heatgeek suggest heating the whole house for best efficiency with heat pumps unless you have lots of insulation between the rooms, or wings to the house.
I'm absolutely sold on this for our ~2800 sq ft 2002 build house in Newark, Nottinghamshire to replace a 36kW boiler. We have 10mm plastic microbore fed from a 28mm copper main, so it's good to see the micropore works well for you. The only issue I have is the quotes I've had so far are £15k (so still £7.5k to pay) which feels steep when most of my rads are already upgraded (DIY) and the Vaillant heat pump itself is around the £5-6k mark. Agreed I'd probably need a new water cylinder (I have a Megaflow currently) but I reckon it's no more than £7k all-in for equipment plus ancillaries - so the £8k I'm being asked for installation feels like a rip off. Is anyone else getting daft quotes for their houses? Interesting also to hear about over-sizing. Our Vaillant 36kw gas condensing boiler can only modulate down to 6.3kW, so very often it's cycling on and off unless in the dead of winter - and even then it struggles to ramp down far enough to avoid cycling. Having a system which just ticks along putting in a few kWs continuously would suit us far better.
I think the installers are busy at the moment, because of the increased grants being offered, so you may have to keep shopping around. To get a good idea of the material cost search on midsummer wholesale heat pump kit builder and it will build an itemised kit for you. Remove the buffer tank and the extra circulation pump if yours is a direct system. The VAT free total you get needs to be discounted for a trade purchase. I think this will be at least 20% less (based on other cost searches I have done). My quick check shows that the whole material cost for a 7Kw Vaillant is about £6k including a new tank. This at least lets you know what they are charging for installation! Most gas boiler installations are very inefficient because they have been grossly over sized so a correctly installed heat pump will save even more. My property is over 200sq m and we have a Vaillant 7Kw so you will likely be okay with a 5Kw (which can output more than 6Kw). That would save more money. Have you downloaded your gas usage to work out your heat input into the house? I cover that on my first video on my installation. Good luck
You have to appreciate that where hot water use is high, the heat demand would exceed the normal ‘just enough’ to heat the house calculations. Heating 250 litres of hot water will consume 10 kWh to raise it from 10 degrees C to 50. And throughout that time no heat is supplied to the radiators. A 5 kW heat pump would cycle in and out of hot water mode for up to 3 hours to achieve the hot water at the slow rate for efficiency. And when temperatures are just above freezing and there is dampness in the air you will experience defrost mode cycling. When this occurs you lose heat going to the radiators. In fact the heated water is cooled to provide the heat to melt the ice on the heat exchanger outside. If you live in an area of frequent mist in winter you might even need to up size the heat pump so that the heat exchanger is not as cold when working to avoid this freezing issue. Once outside temperatures fall below zero the problem goes away.
It is a good point about the hot water being an extra to the heat loss calculations. The data for the coldest day and the overall year did include hot water. The Vaillant defrost cycle is very quick, about 5 mins, so I haven't seen it causing a big problem so far.
Really interesting video on the basis that you have a large house and microbore (horrible scenario and the same as I have here!!). Wondered if you have looked at the tomato lifestyle tariff, I moved to it a month ago, 6 hours @ 5p, 4 hours at 13.4p and peak at 23.16p plus a lower standing charge? Made sense for me!
Would be interested in the Heat Loss calculation worksheet. I would also like to know what Adam from Heat Geeks thinks of your instal and data outputs. I have a 2001 house with plastic pipes and copper microbore tails to rads. Adam suggested that plastic and microbore inhibit flow rates. Your COP of 3.8+ suggests that microbore does not cause any significant issue.
Thanks for your comment. I will do a short video on the heat loss work sheet. I did give Heat Geek a plug in the original video and, I believe, Adam gave me a like. I would also love to hear his thoughts. In working out I could install the system without a buffer tank I drew very heavily on the information from Heat Geek. They state that the maximum velocity in the pipes should not exceed 1.5m/s. Using that information I worked out 2 radiators with separate microbore feeds from a 22mm backbone would be enough to ensure adequate flow. To be safe, I keep 6 radiators open. I agree my COP, measured through an independent system, is really good and would probably be over 4 if I didn’t run it at the coldest times.
It’s funny how much your home mirrors mine, and I’m still trying to cost justify putting in the heat pump. My home is a 2002 build with micro bore, 4 bedrooms, I have solar and battery storage and am on intelligent octopus go. My projections come out very similar, maybe a little less than yours in terms of savings, so that’s encouraging. But with a new hot water tank, 11 new radiators (not changing 6 of them) and a 5kw valiant, I’m still looking at around £19K before grant and the return on the investment doesn’t add up…upwards of 20 years. I’m working closely with Heat Geek trying to optimise the system, looking at 50 degree flow temp for reduced cost rather than driving efficiency etc…. Just finding it hard to spend £12K of my own money for £300-£400 a year saving.
Thanks for your comment. Your quote does seem expensive to me. My system installed just over a year ago cost £11700 before the grant. That included 6 new radiators, a volumiser, and the open energy monitor which is about £500. I also had the bigger, 7kw, heat pump Midsummer Wholesale does a very good kit builder for a heat pump which includes all the material you need. I have just put together a kit based on the 5Kw Vaillant, including a 200L tank and the VAT free cost is £6939. Also the cost they quote me is not the trade price as you have to be a registered merchant to get that, so I would expect it the cost to be at least 10% less than this. The radiators will also be VAT free if installed at the same time. Just looking at Screwfix a 600x1200 type 22 is only £61 before VAT. So your material cost is still probably below £7000. You might have to keep looking for a competitive installer.
Thanks for replying, wow, I would bite their arm off if they had said £11K. They are quoting me £8.8K alone for the labour (11 rads, new heat cylinder, the pump and a volumiser with a second pump). Did you use Heat Geek at all when you did yours? I find them very knowledgable and extremely responsive to feedback, just not sure that the costs make sense. But it’s good to know a system of that size should be affordable. Did you size to run at DT50? I had them quote for both DT50 and DT40, it just added more radiator capacity but they recommended going with DT50 still.
@@SoullessAndSynthetic I did contact Heat Geek installers, not heat geek directly, but they were massively busy and I didn’t get any quotes as they were too busy. I wonder if that is the current problem as heat pump installs increase due to the grant. The Heat Geek online material is excellent. I used their information to improve my knowledge. I sized my system for DT 40 and it works at that DT. Get bigger radiators, or add radiators, to get to a DT of 40 or below, in my view.
No surprise to hear that your quote was from Heat Geek. They are very, very expensive. You could say you get what you pay for, but not the premium they are ask for. Your house sounds similar to mine (but no solar/battery yet) and my Octopus quote is £3500 after £7500 grant taken off (could come out less as they have over egged a couple of things). When you work out ROI, bear in in mind that you would need and additional gas boiler replacement in the lifetime of the HP as they last about half as long.
I would be very interested to see how heat loss is calculated as I'd like to work out mine. I'm having a survey done in early December and I hope that I won't have to have the argument with them about this, but I could do with being armed just in case. Already with Octopus and it is they who will be quoting (well actually they have already quoted but some extras not quoted for will be required in my case). Thanks!
There are some tools out there like Heat Punk that is recommended but I haven't used it. We will produce a video on doing the heat loss calcs yourself.
The easy way is to establish the u-values of all the elements of the outer skin of the house. But this can be fraught with problems where you have single brick walls, I.e. non cavity. The Building Research people at Watford have been unable to give any simple rule of rhumb guidance with research in test conditions resulting in vales over 2 to about .8 depending on brick type and mortar voids. Thousands of London’s 1930 semis have flank walls without cavities. Water ingress hasn’t been a problem because they are built so close together but they are in need of major insulation upgrades.
@@briangriffiths1285 Thanks! I do have brick and block construction (1952 build) so perhaps it won't be so hard. I'll look into it in preparation for my survey.
@@robynrox Sadly those will be clinker blocks rather than later insulating blocks. Even with the cavity filled you might have u-values higher than .5 unless you can add some further insulation?
@@briangriffiths1285 Yes, it's clinker blocks. I could add some more insulation to the loft fairly cheaply, I think. I know it's possible to have the outside clad but I've heard that's really expensive and I don't think I want to go there. I do know that I'm paying for an average of 6456 kWh of gas per year for central heating and hot water only, averaged over the last two years with the room thermostat set to 19C during the day with a setback during the night of 9.5C, and it's a three-bed terrace. Gas boiler is a combi and is being driven by a nest wired up to use opentherm.
It is interesting that your system works so well with microbore pipework. One of the things I was concerned about is the upheaval of having to change all my heating to normal pipework when eventually I do need to replace my boiler. I suspect the grant for heat pumps will carry on until it is illegal to fit gas heating, to try to keep demand high enough to help the industry transition.
I had some intsallers wanting to rip out all the plumbing but they could never explain why in logical, engineering terms.It was just hearsay. I have proved microbore is fine in y situation.
I agree that is an option and I recommend everyone make their own decision based on the assumptions they are happy to make. As we know gas prices are quite volatile.
@@hughrattray9354given how electricity prices are mostly based on gas prices, the tariffs should track each other. It seems a little unfair to mention the plethora of electricity tariffs and not mention the single decent gas tariff available.
@@Biggest-dh1vr I did not spend a lot of time on the tariffs so I am not sure if any of them are the best available. I did forget to mention the Octopus Go tariff which would lower electricity prices for some. The outline is there to make their own assumptions. There was no intention to be unfair.
Hi James, a very interesting video thank you 👍 You say/mention that you have microbore plumbing, no problem, but can i ask is it 10mm or 8mm microbore? Like you we’re also doing everything we can to ‘go green/er’…. Solar, batteries, EV, solar diverted for hot water etc. But as we have 8mm microbore as i understand it we we can’t have a heat pump 😢
I have 10mm microbore. 8mm makes it a bit more challenging and you are likely to have to have more radiators open all the time. It also depends how big a heat pump you need as the lower power heat pumps require lower flow rates and make life easier with 8mm pipes.
Do you think this would work with a mix of 8mm and 10mm microbore on on a 1960s 5bed house ? I have seen another video with 8mm microbore which seems to indicate that this would work. Octopus indicated that it wasn't feasible!!
Possibly it could work but there are a few things to consider. Smaller heat pumps have lower flow rates which would be more suited to microbore pipes. The radiators need their own microbore feed from a bigger diameter backbone so the flow rate for each radiator stays below 1.5 m/s. (I calculated that 2 radiators with 10mm microbore would be enough flow rate for the 7 Kw Vaillant - more is better though) You might have a balancing problem as the radiators with 10mm microbore would get much higher flow rate than the 8mm. Could you upgrade the 8mm microbore to 10?? The reason I have put these videos out is to challenge the notion that microbore doesn’t work. Good luck with your project.
We would absolutely love to go to India this winter-spring. If we are able to go, we would like to go to Kashmir to see the snow leopards, Gujarat to see the lions. Sadly my wife has macular degenerative eye problems which necessitates injections in her eye. If it improves we will make it. Thank you for asking, as you know we absolutely love your country.
@JamesRattray These all are good places to visit. You should also include zanskar Valley if you plan to go to kashmir, it's a hidden gem with beautiful landscape. And I hope your wife's condition continues to improve and that you have a nice trip in India ❤️
Great. But it’s Go for EV drivers, Flux for Batteries and Cosy for heat pumps. I’d be interested to see the difference between Open energy monitor and My Vaillant readings. My Vaillant is currently giving a COP above 4 but I’m unclear where that’s measured. I have a simple system so I wonder why it would be inaccurate.
The Vaillant tends to give a very optimistic COP value. Cop should be worked out by dividing the total heat output by the energy going in. Vaillant add the energy in to the total heat output and then divide it by the heat output.
I assumed that everyone will have an electric connection and they will keep it. If you move away from gas heating to a heat pump it would be sensible to disconnect from gas in which case you will save the cost of the standing charge as well as the gas cost.
Hugh , have you tried "semi full house" monitoring ie having the bedrooms not in use at say 15/16C rather than the full house bed room temps of say19C to investigate what your COP would be?
I haven't tried that but when the family were last home I got complaints that the bedrooms were too hot so I had to reduce the temperatures at night. No one wants their room at 20C unless they are using it as an office. It is a good suggestion. I will take stock and consider what further experiments to do.
Our house which is much smaller than yours has a central 22mm manifold with 7 radiators off it fed by 8mm copper microbore. Am I being overly optimistic in expecting a heat pump to deal with this do you think?
I think with 8mm pipes you would want all 7 radiators open. You would also need a much smaller heat pump which would have lower flow rates. I will have a look at the data later.
The actual performance seems to be very close to the specification. I haven't completed a specific analysis of it so I will have a think about how I can do it.
On the coldest day of the year, which we looked at in the video, the average energy draw was 1Kw. The maximum I have seen is 3Kw during start up. The minimum when it is runnig is about 600watts.
Thanks for the question. I do calculate the cost for three common scenarios in the video. I have also put my calculations in the notes for this video. Have a look and let me know if you have any questions.
The heat los calculations for the whole house heated to 20C with -2C outside is just under 8Kw which is still easily within the capability of the 7Kw Vaillant. The truth is that I don't think many people want to heat every room in the house ro 20C all the time so the normal usage will be below that figure even if the house is full
@@deamer44 The outside temperature to use for heat loss calculations depends on your location. If you use the MCS heat loss calculator it will use your postcode and altitude to come up with the number. The figure for my house is -2.5C. For Glasgow it is -3.9C. If you live at altitude it will be higher.
The global warming potential of the leaked methane from the gas network and during extraction is huge and could almost double the effect of gas usage. it may only be 1% of the of the gas lost but methane 80 time more powerful green house gas than CO2. heat pumps do indeed massively reduce emissions.
you can do the same with a gas boiler and have open therm and weather compensation tech on yhe boiler it stays the same temp in the house, it could be -5c outside and the rads will be hot to keep the house warm or it could be 15c and the radiators be luke warm as theres not much demand for heat.
I must admit I have only become aware of that recently and I agree if you do that you are likely to gain efficiency on your gas boiler and have a more comfortable house
The problem with agile is that prices change every day so the results will be changing. Hopefully the software for the heat pump will be able to automatically choose the best time to run based on agile prices.
Not overly sure on the assumption you have here? The Summer COP he had was 2.6, grid average of CO2 per kWh for the last 12 months was 175g = 67g/kWh of heat. A gas boiler with a COP of 0.85 = 215g/kWh so ASHP, on heating hot water only, is 3.2 times less CO2 than a gas boiler. Thats all before you add in home solar etc.
Nobody needs a heat pump to cover ALL the heat losses because the house is full of people pets and appliances (TVs fridges computers washing machines etc etc) that use electricity which eventually gets converted to heat. And let's not forget solar gain and Christmas jumpers - this is why MCS is complete bollocks and will ALWAYS oversize just as the gas industry did all these years. Please re-do your calcs including the amount of electricity used for everything else.
I agree MCS over estimates heat needs. My daily average electricty usage without the heat pump and EV is about 10Kwh so that all ends up as heat in the house. We also have a lot of SE facing glass which alllows a lot of heat in on a sunny winters day.
Outstanding Video!!!! Well done you. High praise from a retired "Building Services Controls Engineer". Excellent details of the whole process. Will definitely be watching more of your videos, as this is the first I've seen, and may be questioning you in the future, although I think you may have covered everything already!!!!!🤫
Thank you.
Thanks for your encouraging comments.
I am happy to give my views on any questions.
A very informative and persuasive account of your experience of living with a heat pump one year on following installation. It's converted me. I'm now going to seek quotes for a heat pump for my house to replace my gas boiler.
That is very good to hear. I am sure you won't regret it.
Brilliant work gentlemen!
This mirrors my experience in just about every way.
I also have a 7kW Arotherm plus with microbore which I've documented extensively on my channel.
Largest heat pump quote i got was for a 16kW unit!😮
Thanks, I have seen many of your videos. Hopefully we can persuade others to move to green tech.
It's difficult to explain how nice and warm our house is with a heat pump. Similar system 7kW Arotherm + with microbore on OEM too! Great video and detail - thanks for sharing.
I agree, it has transformed our house in winter. Sorry I can't work out what you mean by OEM.
@@hughrattray9354Open Energy Monitoring OEM
5kW here and house (with 10mm plastic microbore) has never been toastier nor costing as little to heat, I absolutely love it. The heat is so much more even/pleasant too, I find. And yes, loving the OEM kit too, so much extra info (OEM is the OpenEnergyMonitoring system you use Hugh, to answer your question above).
Thanks James I agree I was persuaded to put 8.5 kw heat pump and I calculated a heat loss under
5KW . Thanks for pointing out other section of open energy monitor with the scatter graph which confirms a 5 kw would have done easily . As per usual very informative cheers Andrew
Great video. Agile tariff works out cheapest for us on our (oversized) heat pump and EV.
Interesting. How do you control the heat pump with the varying agile tariff. Do you have to do it manually or is it automated?
Good video as always James, when we were on the Cosy tarif we did the hot water in the 1pm slot but. We're now finding the Tracker tarif to be overall cheaper this last year and no stress having to load shift.
Good to hear that the load shift is not a problem. Do you know what your SCOP is?
@@hughrattray9354 I don't have an up to date scop as we made another change recently (replaced towel rails with more k2s) but today with 8° outdoor and 21.5° indoor we have cop of 4.3
Very interesting regarding your experience on tariffs. Hugh my brother is hte presenter, I am the cameraman and audience. Really appreciate the fact you enjoy the videos.
Love watching your videos James, they were an inspiration for my own 5kw Vaillant install in the summer. My plastic 10mm microbore has been no barrier and the system is working happily since install. Only one issue I disagree with you on, Octopus energy. They used to be good and well recommended but no more. They arranged for my Gas meter to be removed and capped in May, it got removed fine but they are still billing me for the standing charge and estimated usage. I transferred over to E.ON EV tariff (7 hours at 6.9p at night and better solar payments) at the end of July, still no final bill from them. I've emailed several times, called and emailed complaints, each time it takes two days for a reply and promises it'll be fixed. It's not a one off either, my dad transferred electric and gas to a new provider, his transfer worked great and final bill came indicating they'd pay credit directly into account on a particular date. Three weeks later no credit, no helpful support. I think they've expanded too much and struggling.
It is good to hear your microbore system is working well. I think it helps to dispel the myth that you have to rip it all out.
Sorry to hear of your bad experience with Octopus. it is also good to see that E.ON are offering good tariffs too
Thanks james for taking the time to provide an update - thorough as always! As you covered previously - worth downloading smart meter data for your current gas boiler as a good way to sanity check your heat loss calcs - not forgetting that most boilers will be running sub 90% efficiency! 7kw ashp should be good for most houses. Potential savings from octapus cosy looks very interesting. 👍
I agree, it is a very useful way of getting another view of the heat loss from your house.
You might struggle to get Octopus to let you have a small heatpump. MCS rules are applied rigidly, and they point blank refused me an 8kw (which can modulate much lower than the 9kW monobloc). My calcs based on gas use the said we only needed 7kw max (90s detached 4-bed, fairly well insulated, also microbore). Only cost me £1750 after the grant though 😊.
@@DomSta03 Yes I had some installers taking the same attitude so I kept looking. The install needs to be right.
Totally agree - I cannot see why historical gas usage wouldn't be the primary guide to how big a ASHP is required, especially if you were able to run the gas boiler with a nice low flow temp over a couple of winter months.
Another very informative video. Just wanted to point out that the calculation for the cosy tariff assumes 105% use 75+25+5 ! So the assumption could work a little cheaper still.
Thanks. As you say the error makes the calculations slightly more conservative
Brilliant video with lots of well thought out data. Really good to hear you talking about systems being oversized as it's a common theme I've seen on other owners videos. Realistically if the temperature is lower than design temperature for a day or two it will just cost a bit more to run. This laziness of installers will only hinder the uptake as the units are physically bigger and cost hundreds of pounds more.
I agree. I don't think the heat loss calculations are taken seriously enough. If they are done right they ensure you get the right sized heat pump.
I suspect over sized gas boilers have been fitted for years too.
@@hughrattray9354Heat loss calcs can also result in oversized units. MCS rules are applied pretty inflexibly.
@@DomSta03 That is true but there are a few things, particularly air changes per hour, that have a massive impact and are largely guesses so I think you can influence the result by questioning the figure used.
I also got the impression that many installers just guessed the heat loss by looking at the property and then followed with the heat loss calculations
@@hughrattray9354 Oversizing is guaranteed by the MCS regulations - heat loss calculations are one small part of the picture. They take no account of so many other factors like solar gain, household appliances, people or pets. The biggie is air changes per hour based on the date the house was built - how fucking accurate is that?
Thanks, James for sharing your experience with heat pumps. I see you also have a Powerwall battery. Does it run the heat pump when you come off the overnight cheap rate at 05:30? I'd imagine doing so would bring your energy bills down even further than shown in the video.
Yes the Powerwall runs the whole house and it is topped up by any solar there is. Last winter the Powerwall covered most days and I only had to draw from the grid on cold and cloudy days.
heat punk is a fantastic free heat loss calculation program if you do a separate video on the subject. it allows you to play with the fabric of the building and see the gains you would make replacing a window or adding insulation.
Coincidentally, I spent a couple of hours yesterday putting a plan into Heat Punk and comparing it with my own calculation. I am very impressed and will feature it in any video on heat loss calculations.
Excellent video. Thanks.
Would you mind if I show this to our local eco group as a group?
Please do. I am keen to get the message out as far as possible.
Great video, very interesting! Microbore with no buffer tank and no glycol - see, it can be done! Even more evidence that installers are overdoing it to (1) reduce their risks by using bigger HPs, buffers, etc, and (2) gain extra profit for kit and associated labour, both at the expense of the customer!
Spot on with the analogy of a too big car engine. I would also add that HPs modulate down but the bigger they are the less they can modulate down - so when you only need a low kW output a big HP will keep cycling which is less efficient. Poor performance is also because of having buffers/LLHs when not needed, especially when combined with a second circuit pump which is "fighting" against the HP's own pump.
Design is critical with a HP solution. I always say that if you get it wrong with a gas boiler you make a 10% loss in efficiency that nobody will notice but if you get it wrong with a HP you could easily lose 200% efficiency which could mean a cold house!
With "reduced occupancy", are you using TRVs to turn off the unused rooms? Amid some saying to run "open circuit" and not use TRVs (which I am not clear on why), I too have 2-3 rooms I sometimes don't want to heat for days or weeks on end. Is doing this and not having a buffer/LLH mean too much stress on the HP potentially reducing its longevity?
On the point of the grant being generous, I agree it is but I also think that installers are somewhat taking advantage (as they always do) so that much of the grant is consumed/lost. Plus the prices may come down as the installations go up due to economies of scale and knowledge gained to optimise installations. Still, it is a good time to get one though.
I am not sure if this reply was uploaded before so I am trying again.
Great comments. I think many installers never look back to see how their installs perform so they err on the side of playing it very safe. I was told by my friend’s installer that many people in the industry were looking at my first video (10 months ago) on my installation. It was creating a lot of discussion and, perhaps, making them think again.
Bigger heat pumps modulate more and they also require higher flow rates which would have been more of a challenge for my system.
I agree with your comment about the design stage and a crucial part of that is a proper heat loss calculation which many installers don’t seem to do.
You are correct about the heat loss with reduced occupancy being 3.7Kw. That is the more common state but it is good to be able to accommodate the family when needed. I have a Honeywell Evohome system controlling the TRVs so all rooms are frost protected and can be controlled separately.
All the living rooms have the radiators continually open so that is at least 7 radiators. I also have a 25ltr volumiser tank. This allows plenty of flow for the 7Kw and the cycle time is long so I don’t believe this causes any stress on the HP.
I think the number of HP being installed has picked up a lot so the installers are able to charge high prices. Unfortunately this is not helping the reputation of heat pumps. If you google heat pump prices they are not as expensive as you would think and they have no VAT.
Do you have a heat pump? Or are you planning to get one.
I was going to ask what you just mentioned in regards how does one calculate a heat loss scenario, so will look forward to that video .
We willtry and get a video out in the next coupl of weeks.
@@hughrattray9354 Thank you , I live alone in a small three bedroom terraced house and only use a couple of rooms in the house , so I have been arguing with myself of which way to go = air to water or air to air , so I’m totally confused in which one would suit me best .
@@KavanOBrienif you have radiators already air to water is probably easier.
Air to air could be quite disruptive.
@@hughrattray9354 If the radiators have to be bigger as an example is that also disruptive, I live alone so it really makes no difference of the upheaval, but in my situation heating areas in the house I don’t really use seems pointless, I don’t know myself about the heat pump scenarios, but I keep asking myself surely air to air for me seems correct, of course I could be wrong very hard to get an opinion from an independent person , obviously any installer is thinking about which is best for themselves.
@heatgeek suggest heating the whole house for best efficiency with heat pumps unless you have lots of insulation between the rooms, or wings to the house.
I'm absolutely sold on this for our ~2800 sq ft 2002 build house in Newark, Nottinghamshire to replace a 36kW boiler. We have 10mm plastic microbore fed from a 28mm copper main, so it's good to see the micropore works well for you. The only issue I have is the quotes I've had so far are £15k (so still £7.5k to pay) which feels steep when most of my rads are already upgraded (DIY) and the Vaillant heat pump itself is around the £5-6k mark. Agreed I'd probably need a new water cylinder (I have a Megaflow currently) but I reckon it's no more than £7k all-in for equipment plus ancillaries - so the £8k I'm being asked for installation feels like a rip off. Is anyone else getting daft quotes for their houses?
Interesting also to hear about over-sizing. Our Vaillant 36kw gas condensing boiler can only modulate down to 6.3kW, so very often it's cycling on and off unless in the dead of winter - and even then it struggles to ramp down far enough to avoid cycling. Having a system which just ticks along putting in a few kWs continuously would suit us far better.
I think the installers are busy at the moment, because of the increased grants being offered, so you may have to keep shopping around.
To get a good idea of the material cost search on midsummer wholesale heat pump kit builder and it will build an itemised kit for you. Remove the buffer tank and the extra circulation pump if yours is a direct system. The VAT free total you get needs to be discounted for a trade purchase. I think this will be at least 20% less (based on other cost searches I have done).
My quick check shows that the whole material cost for a 7Kw Vaillant is about £6k including a new tank. This at least lets you know what they are charging for installation!
Most gas boiler installations are very inefficient because they have been grossly over sized so a correctly installed heat pump will save even more.
My property is over 200sq m and we have a Vaillant 7Kw so you will likely be okay with a 5Kw (which can output more than 6Kw). That would save more money.
Have you downloaded your gas usage to work out your heat input into the house? I cover that on my first video on my installation.
Good luck
You have to appreciate that where hot water use is high, the heat demand would exceed the normal ‘just enough’ to heat the house calculations. Heating 250 litres of hot water will consume 10 kWh to raise it from 10 degrees C to 50. And throughout that time no heat is supplied to the radiators. A 5 kW heat pump would cycle in and out of hot water mode for up to 3 hours to achieve the hot water at the slow rate for efficiency. And when temperatures are just above freezing and there is dampness in the air you will experience defrost mode cycling. When this occurs you lose heat going to the radiators. In fact the heated water is cooled to provide the heat to melt the ice on the heat exchanger outside. If you live in an area of frequent mist in winter you might even need to up size the heat pump so that the heat exchanger is not as cold when working to avoid this freezing issue. Once outside temperatures fall below zero the problem goes away.
It is a good point about the hot water being an extra to the heat loss calculations. The data for the coldest day and the overall year did include hot water.
The Vaillant defrost cycle is very quick, about 5 mins, so I haven't seen it causing a big problem so far.
Really interesting video on the basis that you have a large house and microbore (horrible scenario and the same as I have here!!). Wondered if you have looked at the tomato lifestyle tariff, I moved to it a month ago, 6 hours @ 5p, 4 hours at 13.4p and peak at 23.16p plus a lower standing charge? Made sense for me!
I have just had a look. That is an excellent tariff with a low standing charge.
Would be interested in the Heat Loss calculation worksheet. I would also like to know what Adam from Heat Geeks thinks of your instal and data outputs. I have a 2001 house with plastic pipes and copper microbore tails to rads. Adam suggested that plastic and microbore inhibit flow rates. Your COP of 3.8+ suggests that microbore does not cause any significant issue.
Thanks for your comment. I will do a short video on the heat loss work sheet.
I did give Heat Geek a plug in the original video and, I believe, Adam gave me a like. I would also love to hear his thoughts.
In working out I could install the system without a buffer tank I drew very heavily on the information from Heat Geek. They state that the maximum velocity in the pipes should not exceed 1.5m/s. Using that information I worked out 2 radiators with separate microbore feeds from a 22mm backbone would be enough to ensure adequate flow. To be safe, I keep 6 radiators open.
I agree my COP, measured through an independent system, is really good and would probably be over 4 if I didn’t run it at the coldest times.
It’s funny how much your home mirrors mine, and I’m still trying to cost justify putting in the heat pump. My home is a 2002 build with micro bore, 4 bedrooms, I have solar and battery storage and am on intelligent octopus go. My projections come out very similar, maybe a little less than yours in terms of savings, so that’s encouraging. But with a new hot water tank, 11 new radiators (not changing 6 of them) and a 5kw valiant, I’m still looking at around £19K before grant and the return on the investment doesn’t add up…upwards of 20 years. I’m working closely with Heat Geek trying to optimise the system, looking at 50 degree flow temp for reduced cost rather than driving efficiency etc…. Just finding it hard to spend £12K of my own money for £300-£400 a year saving.
Thanks for your comment.
Your quote does seem expensive to me. My system installed just over a year ago cost £11700 before the grant. That included 6 new radiators, a volumiser, and the open energy monitor which is about £500. I also had the bigger, 7kw, heat pump
Midsummer Wholesale does a very good kit builder for a heat pump which includes all the material you need. I have just put together a kit based on the 5Kw Vaillant, including a 200L tank and the VAT free cost is £6939. Also the cost they quote me is not the trade price as you have to be a registered merchant to get that, so I would expect it the cost to be at least 10% less than this.
The radiators will also be VAT free if installed at the same time. Just looking at Screwfix a 600x1200 type 22 is only £61 before VAT. So your material cost is still probably below £7000.
You might have to keep looking for a competitive installer.
Thanks for replying, wow, I would bite their arm off if they had said £11K. They are quoting me £8.8K alone for the labour (11 rads, new heat cylinder, the pump and a volumiser with a second pump). Did you use Heat Geek at all when you did yours? I find them very knowledgable and extremely responsive to feedback, just not sure that the costs make sense. But it’s good to know a system of that size should be affordable. Did you size to run at DT50? I had them quote for both DT50 and DT40, it just added more radiator capacity but they recommended going with DT50 still.
@@SoullessAndSynthetic I did contact Heat Geek installers, not heat geek directly, but they were massively busy and I didn’t get any quotes as they were too busy. I wonder if that is the current problem as heat pump installs increase due to the grant.
The Heat Geek online material is excellent. I used their information to improve my knowledge.
I sized my system for DT 40 and it works at that DT. Get bigger radiators, or add radiators, to get to a DT of 40 or below, in my view.
No surprise to hear that your quote was from Heat Geek. They are very, very expensive. You could say you get what you pay for, but not the premium they are ask for. Your house sounds similar to mine (but no solar/battery yet) and my Octopus quote is £3500 after £7500 grant taken off (could come out less as they have over egged a couple of things).
When you work out ROI, bear in in mind that you would need and additional gas boiler replacement in the lifetime of the HP as they last about half as long.
@@hughrattray9354 Are you sure about DT40 - normally DT5 to DT7?
I would be very interested to see how heat loss is calculated as I'd like to work out mine. I'm having a survey done in early December and I hope that I won't have to have the argument with them about this, but I could do with being armed just in case. Already with Octopus and it is they who will be quoting (well actually they have already quoted but some extras not quoted for will be required in my case). Thanks!
There are some tools out there like Heat Punk that is recommended but I haven't used it. We will produce a video on doing the heat loss calcs yourself.
The easy way is to establish the u-values of all the elements of the outer skin of the house. But this can be fraught with problems where you have single brick walls, I.e. non cavity. The Building Research people at Watford have been unable to give any simple rule of rhumb guidance with research in test conditions resulting in vales over 2 to about .8 depending on brick type and mortar voids. Thousands of London’s 1930 semis have flank walls without cavities. Water ingress hasn’t been a problem because they are built so close together but they are in need of major insulation upgrades.
@@briangriffiths1285 Thanks! I do have brick and block construction (1952 build) so perhaps it won't be so hard. I'll look into it in preparation for my survey.
@@robynrox Sadly those will be clinker blocks rather than later insulating blocks. Even with the cavity filled you might have u-values higher than .5 unless you can add some further insulation?
@@briangriffiths1285 Yes, it's clinker blocks. I could add some more insulation to the loft fairly cheaply, I think. I know it's possible to have the outside clad but I've heard that's really expensive and I don't think I want to go there. I do know that I'm paying for an average of 6456 kWh of gas per year for central heating and hot water only, averaged over the last two years with the room thermostat set to 19C during the day with a setback during the night of 9.5C, and it's a three-bed terrace. Gas boiler is a combi and is being driven by a nest wired up to use opentherm.
It is interesting that your system works so well with microbore pipework. One of the things I was concerned about is the upheaval of having to change all my heating to normal pipework when eventually I do need to replace my boiler. I suspect the grant for heat pumps will carry on until it is illegal to fit gas heating, to try to keep demand high enough to help the industry transition.
I had some intsallers wanting to rip out all the plumbing but they could never explain why in logical, engineering terms.It was just hearsay. I have proved microbore is fine in y situation.
For the gas comparison, you might want to use the Octopus Gas Tracker tariff, which is currently about 5.1p per kWh for gas?
I agree that is an option and I recommend everyone make their own decision based on the assumptions they are happy to make. As we know gas prices are quite volatile.
@@hughrattray9354given how electricity prices are mostly based on gas prices, the tariffs should track each other. It seems a little unfair to mention the plethora of electricity tariffs and not mention the single decent gas tariff available.
@@Biggest-dh1vr I did not spend a lot of time on the tariffs so I am not sure if any of them are the best available. I did forget to mention the Octopus Go tariff which would lower electricity prices for some. The outline is there to make their own assumptions. There was no intention to be unfair.
@@Biggest-dh1vr I thought @hughrattray9354 was being very helpful by giving us examples.
Hi James, a very interesting video thank you 👍
You say/mention that you have microbore plumbing, no problem, but can i ask is it 10mm or 8mm microbore? Like you we’re also doing everything we can to ‘go green/er’…. Solar, batteries, EV, solar diverted for hot water etc. But as we have 8mm microbore as i understand it we we can’t have a heat pump 😢
I have 10mm microbore. 8mm makes it a bit more challenging and you are likely to have to have more radiators open all the time. It also depends how big a heat pump you need as the lower power heat pumps require lower flow rates and make life easier with 8mm pipes.
Do you think this would work with a mix of 8mm and 10mm microbore on on a 1960s 5bed house ? I have seen another video with 8mm microbore which seems to indicate that this would work. Octopus indicated that it wasn't feasible!!
Possibly it could work but there are a few things to consider. Smaller heat pumps have lower flow rates which would be more suited to microbore pipes.
The radiators need their own microbore feed from a bigger diameter backbone so the flow rate for each radiator stays below 1.5 m/s. (I calculated that 2 radiators with 10mm microbore would be enough flow rate for the 7 Kw Vaillant - more is better though)
You might have a balancing problem as the radiators with 10mm microbore would get much higher flow rate than the 8mm.
Could you upgrade the 8mm microbore to 10??
The reason I have put these videos out is to challenge the notion that microbore doesn’t work.
Good luck with your project.
Hey, James, when are you coming back to India? Which parks safari are you going to do this time
We would absolutely love to go to India this winter-spring. If we are able to go, we would like to go to Kashmir to see the snow leopards, Gujarat to see the lions. Sadly my wife has macular degenerative eye problems which necessitates injections in her eye. If it improves we will make it. Thank you for asking, as you know we absolutely love your country.
@JamesRattray These all are good places to visit. You should also include zanskar Valley if you plan to go to kashmir, it's a hidden gem with beautiful landscape. And I hope your wife's condition continues to improve and that you have a nice trip in India ❤️
@@doglovers814 Thank you, I really appreciate the advice and good wishes for my wife.
Great. But it’s Go for EV drivers, Flux for Batteries and Cosy for heat pumps.
I’d be interested to see the difference between Open energy monitor and My Vaillant readings. My Vaillant is currently giving a COP above 4 but I’m unclear where that’s measured. I have a simple system so I wonder why it would be inaccurate.
The Vaillant tends to give a very optimistic COP value. Cop should be worked out by dividing the total heat output by the energy going in. Vaillant add the energy in to the total heat output and then divide it by the heat output.
Forgive me if I am wrong but did you add the daily standing charge for gas supply but omitted it for electric?
I assumed that everyone will have an electric connection and they will keep it. If you move away from gas heating to a heat pump it would be sensible to disconnect from gas in which case you will save the cost of the standing charge as well as the gas cost.
@@hughrattray9354I wanted to disconnect my gas, but an induction range was going to cost more than the HP!
@@DomSta03 That sounds crazy - I fitted a modest induction hob at very low cost
Hugh , have you tried "semi full house" monitoring ie having the bedrooms not in use at say 15/16C rather than the full house bed room temps of say19C to investigate what your COP would be?
I haven't tried that but when the family were last home I got complaints that the bedrooms were too hot so I had to reduce the temperatures at night. No one wants their room at 20C unless they are using it as an office. It is a good suggestion. I will take stock and consider what further experiments to do.
Our house which is much smaller than yours has a central 22mm manifold with 7 radiators off it fed by 8mm copper microbore. Am I being overly optimistic in expecting a heat pump to deal with this do you think?
I think with 8mm pipes you would want all 7 radiators open.
You would also need a much smaller heat pump which would have lower flow rates.
I will have a look at the data later.
Check out the @heatgeek pipe flow cheat sheet?
Remind me of your primary pipe work size?
22mm
how do you find the COP (efficiency ) quoted by Vaillant app compares to the open energy monitor ?
The actual performance seems to be very close to the specification. I haven't completed a specific analysis of it so I will have a think about how I can do it.
Hi a quick question when the unit is running what is the average wattage the unit is pulling
On the coldest day of the year, which we looked at in the video, the average energy draw was 1Kw. The maximum I have seen is 3Kw during start up. The minimum when it is runnig is about 600watts.
@@hughrattray9354 thanks for the info
@@hughrattray9354 600W is about 8% - can the 7 Kw Vaillant Arotherm modulate down that low?
@@darrenadams2640 The 600w refers to the electricity input - the output is around 3Kw of heat - The Vaillant can modulate to 25% of maximum
@@hughrattray9354 That's a fair point. Does mean that any heat demand under 25% will cause some cycling. Again, a good reason not to greatly oversize.
How much does it cost you if you remove the solar pv input
Thanks for the question. I do calculate the cost for three common scenarios in the video. I have also put my calculations in the notes for this video. Have a look and let me know if you have any questions.
What diameter mirobore is it? I believe there are two microbore diameters?
Mine is 10mm. 8mm is much more of a challenge
@@hughrattray9354Thanks.
What did your heat loss calc come back as? 7kwh seems incredibly low for an old property with such a large m2
The heat los calculations for the whole house heated to 20C with -2C outside is just under 8Kw which is still easily within the capability of the 7Kw Vaillant.
The truth is that I don't think many people want to heat every room in the house ro 20C all the time so the normal usage will be below that figure even if the house is full
@@hughrattray9354 Aren't you meant to do heat loss to -5C? I've been quoted 12Kw for a 200 SQM house!!
@@deamer44 The outside temperature to use for heat loss calculations depends on your location. If you use the MCS heat loss calculator it will use your postcode and altitude to come up with the number.
The figure for my house is -2.5C. For Glasgow it is -3.9C. If you live at altitude it will be higher.
You can get the octopus go tariff with a battery and no ev.
Good point. I forgot to mention that.
The global warming potential of the leaked methane from the gas network and during extraction is huge and could almost double the effect of gas usage. it may only be 1% of the of the gas lost but methane 80 time more powerful green house gas than CO2. heat pumps do indeed massively reduce emissions.
Good point. I am trying to find accurate information on the leakage of methane and also the amount of energy used by gas to extract and transport etc.
you can do the same with a gas boiler and have open therm and weather compensation tech on yhe boiler it stays the same temp in the house, it could be -5c outside and the rads will be hot to keep the house warm or it could be 15c and the radiators be luke warm as theres not much demand for heat.
I must admit I have only become aware of that recently and I agree if you do that you are likely to gain efficiency on your gas boiler and have a more comfortable house
@@hughrattray9354 This is very true BUT obviously no matter what you do with a gas boiler it can't to (or past) 100% efficiency!
Will it be even cheaper with octopus agile? Just turn off around 4-7pm
The problem with agile is that prices change every day so the results will be changing. Hopefully the software for the heat pump will be able to automatically choose the best time to run based on agile prices.
So in the summer the carbon emission efficiency is only 25% better than gas.
And the winter its 180% more efficient Hmm
Not overly sure on the assumption you have here? The Summer COP he had was 2.6, grid average of CO2 per kWh for the last 12 months was 175g = 67g/kWh of heat. A gas boiler with a COP of 0.85 = 215g/kWh so ASHP, on heating hot water only, is 3.2 times less CO2 than a gas boiler. Thats all before you add in home solar etc.
Nobody needs a heat pump to cover ALL the heat losses because the house is full of people pets and appliances (TVs fridges computers washing machines etc etc) that use electricity which eventually gets converted to heat. And let's not forget solar gain and Christmas jumpers - this is why MCS is complete bollocks and will ALWAYS oversize just as the gas industry did all these years. Please re-do your calcs including the amount of electricity used for everything else.
I agree MCS over estimates heat needs. My daily average electricty usage without the heat pump and EV is about 10Kwh so that all ends up as heat in the house. We also have a lot of SE facing glass which alllows a lot of heat in on a sunny winters day.
wow, u don't have hot water in winter
We have plenty of hot water in winter. What gave you the impression that we do not?