RichardL Posted March 4, 2021 Share Posted March 4, 2021 Hi, I've been reading through and lurking for a while, thinking about changing the heating for my house, triggered by a boiler failure (now fixed) earlier in the year. Interested in the decision - ASHP now, later in the context of RHI changing to grants in 2022. Context I'm in an older property, South Wales so relatively cold/wet location. ~145m2 , Oil fired central heating/hot water ~18-20kWh /(1,891 litres oil) annual equivalent spend on oil averaged from real litres bought over the last couple of years Annual heat loss kW ~10kW Question/thoughts If I went air source this year - upfront investmetnt with the bulk of that coming back via RHI. If I wait until next year (or later, or say when the oil boiler backs up) - the new green grant thing ~£4k On the face of that it would say go air source earlier if I'm going to do it - but Is the current marketplace inflated by RHI to drive the payback into installer upskilling, and will the new lower 4k grant mean the total install costs drop accordingly or just the proportion investment from the end user goes up to meet the gap? Assuming the ASHP market cannot stall - something has to budge? Literally in two minds right now - the ASHP running costs vs. oil are not obviously cheaper - my installer thinks perhaps 20% saving, my back of the envelope calcs come out anywhere between evens and 15%, and that needs heating oil to go above 50p/Litre. Link to comment Share on other sites More sharing options...
Gone West Posted March 4, 2021 Share Posted March 4, 2021 2 hours ago, RichardL said: my installer thinks perhaps 20% saving Welcome to the forum. Well he would wouldn't he. I would wait until the oil boiler is on it's last legs and then consider changing to an ASHP. The longer you wait the more common they will become and cheaper they will be. I don't know where in the country you are but I can't envisage the running costs of an ASHP being cheaper than an oil boiler for a couple of years at least especially if you are in a cold part of the country. Link to comment Share on other sites More sharing options...
RichardL Posted March 4, 2021 Author Share Posted March 4, 2021 Thanks Peter, Thats in my mind too - my numbers come out evens IF oil goes back to 50p (~36-40p now) and electric stays under 14p (~12-13p depending on tariff now) + I'd need to invest 5k after the RHI payback is taken into account. Even if RHI drops from my potential 10k to the 4k grant level over time the market should approach that 4k level - it will have to right or the market for renewable heat will stagnate. I'm sort of in that fear of missing out scenario, but I don't think it makes sense to rush in the next 12 months even with future subsidy likely to be less than current. I'm posting because I'm trying to double check my thinking. Link to comment Share on other sites More sharing options...
Trw144 Posted March 4, 2021 Share Posted March 4, 2021 Have you factored in the likely need to change your heating system? ASHP needs to work on low temperatures to achieve a good COP, so either UFH or low temperature radiators. Link to comment Share on other sites More sharing options...
Temp Posted March 4, 2021 Share Posted March 4, 2021 (edited) 7 hours ago, RichardL said: ~18-20kWh /(1,891 litres oil) annual equivalent spend on oil averaged from real litres bought over the last couple of years That's good data to have. If your oil boiler is 90% efficient it means your house needs about 20*90/100 = 18kWh per year for heating and HW. https://nottenergy.com/resources/energy-cost-comparison/ Oil/kerosene is about 4.6p/kWH. Find out how much you would pay per unit of electricity. That site uses a figure of 19p/kWH. At that rate you would need the COP of the ASHP to average over 19/4.6 = 4 all year to break even. Do your own figures. When you get quotes for an ASHP they should work out your heat loss to correctly size the ASHP. I have some concerns some installers are under estimating heat loss and selling units that are too small. If you end up with a unit that's too small the COP can fall below 2 or lower in winter making it expensive to run or unable to heat the house in cold weather. I would compare thst figure of 18kWh with what the installer calculates the house needs as a sanity check that the sizing is correct. Be aware that if you dont resize the rads the ASHP will need to deliver high flow temperatures and that can reduce the COP. Edited March 4, 2021 by Temp Link to comment Share on other sites More sharing options...
RichardL Posted March 5, 2021 Author Share Posted March 5, 2021 (edited) Hi Temp, Thanks for the responses - yes - aligned with your costing comments - ~20kWh annual heat/hw requirement based on 2 years oil data. I engaged 3x installers to compare quotes - even shared the above data/working for reference. One went crazy and estimated the house needed 2x ASHP in cascade with overall 32kWh capacity - also charged me for the heat loss calcs which were done by a dissolved company still using headed paper whose links to website/phone etc either didn't work or went to another company. Really nasty experience - they got really shirty when I asked any question like - what U values being used to calc Wm2 and how they get from Wm2 to heating capacity required etc quote 'no customer ever asked this before' ? The other two were much more reasonable heat loss calcs and required heating coming out at ~20kWh level which broadly match my numbers & ~15k total install cost before RHI. Calculating a 12kW ASHP requirement. Install cost - all in - inc replacing some rads would end up being the best part of £15k ASHP, £24k GSHP (or 25k ASHP with Mr shonky installer!) Running cost breaks even assuming <~50p/l oil (its 38p right now) and <=14p/kWh electric The question Its RHI going away I'm swaying on. The switch from a potential 10k payback over 7 years if I jump before next April vs 4k grant after April 2022. I'm just wobbling and thinking 15k buys a hell of a lot of house improvements including some re-flooring/and floor insulation etc when my 10 year old oil boiler has at least 5 years life left in it. Also don't want to be a luddite and stick to dying heating technology. Edited March 5, 2021 by RichardL Link to comment Share on other sites More sharing options...
Gone West Posted March 5, 2021 Share Posted March 5, 2021 19 minutes ago, RichardL said: when my 10 year old oil boiler has at least 5 years life left in it. Our oil boiler in the old bungalow lasted over 30 years. 1 Link to comment Share on other sites More sharing options...
Temp Posted March 5, 2021 Share Posted March 5, 2021 6 hours ago, RichardL said: my 10 year old oil boiler has at least 5 years life left in it. My oil boiler is a 13 year old Grant Vortex feeding UFH via a thermal store. I've no intention of replacing it any time soon. I see no reason why it won't do another 10 easily. 1 Link to comment Share on other sites More sharing options...
Onoff Posted March 5, 2021 Share Posted March 5, 2021 6 hours ago, PeterStarck said: Our oil boiler in the old bungalow lasted over 30 years. Going on 23 years here our oil boiler. Mind you, it's like Trigger's Broom! 2 Link to comment Share on other sites More sharing options...
Conor Posted March 5, 2021 Share Posted March 5, 2021 Let's take a step back from the heat loss / demand etc provided by companies trying to sell you something. How well insulated is your house? I'm tired of hearing horror stories of heat pumps installed in houses that simply aren't insulated enough to be effectively heated by a low temperature system. 2 Link to comment Share on other sites More sharing options...
Onoff Posted March 5, 2021 Share Posted March 5, 2021 54 minutes ago, Conor said: I'm tired of hearing horror stories of heat pumps installed in houses that simply aren't insulated enough to be effectively heated by a low temperature system. There's a recent thread on here about that... Link to comment Share on other sites More sharing options...
SteamyTea Posted March 5, 2021 Share Posted March 5, 2021 54 minutes ago, Conor said: I'm tired of hearing horror stories of heat pumps installed in houses that simply aren't insulated enough to be effectively heated by a low temperature system. You mean an inadequately sized system. 1 Link to comment Share on other sites More sharing options...
LSB Posted March 5, 2021 Share Posted March 5, 2021 our boiler was installed in 1983, oil, now making odd noises so looking at replacing. Will have to be oil as house leaks like a sieve and is not really possible to insulate enough as it is 200 years old and single skin. 1 Link to comment Share on other sites More sharing options...
RichardL Posted March 5, 2021 Author Share Posted March 5, 2021 Re the insulation point... Fair point - its not bad - its not a modern house though! Windows are new, Roofs re-tiled with space blanket type, current building regs, insulation, as well as the existing oldschool glass fibre type insulation. However: Concrete solid floors throughout and probably zero insulation - thats not really going to change - perhaps some thin insulation when I swap carpets to wood - but not enough to make UFH make sense. The circa 1800s end is solid 18" thick stone walls + render The circa 50s/60s bit is timber frame + 100mm external wall insulation. Its never going to be perfect. The 19/20kW oil boiler is sufficient to keep it toasty now - especially since the EWI on the timber frame bit. Decision I think I'm pretty much decided ASHP isn't today's project, I think it might work - I just don't need to make the investment right now & chasing an RHI payback doesn't feel like a priority. If the oil price goes up to £1/litre and the electric price stays at 14p/kWh then its a different game of course. Appreciate the sanity check and comments. I asked here in the first place because I saw the 'reality' in replies on other threads. Thank you. Link to comment Share on other sites More sharing options...
Gone West Posted March 6, 2021 Share Posted March 6, 2021 17 hours ago, Conor said: I'm tired of hearing horror stories of heat pumps installed in houses that simply aren't insulated enough to be effectively heated by a low temperature system. 16 hours ago, SteamyTea said: You mean an inadequately sized system. The ASHP may be correctly sized but for many reasons it may not be possible to correctly size the rest of the system in order to heat the house effectively. I may not want quad panel radiators sticking out into the room or walls covered in single panel radiators in order to meet the heating requirement for especially cold periods. Designing a heating system is more than just the physics. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 6, 2021 Share Posted March 6, 2021 12 minutes ago, PeterStarck said: The ASHP may be correctly sized but for many reasons The ASHP is only part of the system. I think this is where confusion comes in. Take UFH as a thermal distribution element. It is a simple component, a pipe loop, usually set in concrete, with warm water passed though it. Then the problems start. It has to be designed so that the power enters the room, not heat up the ground under the building. It has to be designed to deliver the correct power 99% of the time, so different spacing between pipes and different thicknesses of concrete it is set in. There will be some situations where the system is used incorrectly, we have all read about the self inflicted problems Zoot created for himself, and there will be times, as you mention, where part of the system is fine, but other parts are not. This may be as simple as the controller not set up correctly. It may also be necessary to have a combination of thermal emitters in the same room i.e. UFH and a fan assisted radiator. I may have found a solution to fit a wet heating system into my small house without seeing horrible pipework on the surface. Going to have a chat with one of our regular customers who has just done his MCS course and see if he thinks it is viable. Just need to find a physically small, inverter, ASHP that he can buy for me at a reasonable price. Then work out where the buffer tank is going to go. Link to comment Share on other sites More sharing options...
Gone West Posted March 6, 2021 Share Posted March 6, 2021 9 minutes ago, SteamyTea said: The ASHP is only part of the system. Yes exactly my point. What happens if another part of the ASHP heating system is not aesthetically acceptable to you because it is as a result of it being a low temperature system. In that instance it may well be adequately sized but not suitable because it's a low temperature system. If it weren't for the governments intervention in paying people to fit ASHPs in old properties I doubt there would be much interest in ASHPs. They are not the panacea that the government would like to think they are. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 6, 2021 Share Posted March 6, 2021 (edited) 17 minutes ago, PeterStarck said: Yes exactly my point. What happens if another part of the ASHP heating system is not aesthetically acceptable to you because it is as a result of it being a low temperature system That is what system design is all about though; it is not individual component design. The biggest part of the problem is that we have got used to pretty awful heating design systems. This is probably because we retrofitted to existing housing stock in the 60's, 70's and 80's. The skill sets used to do this are very different from what is now needed, but plumbing technicians are not trained to be thermal engineers, nor should they be. So in my opinion, there needs to be 2 parts to designing a heating system: The sizing The plumbing The sizing may also include upgrading the thermal envelope, the plumbing is working out the best route for the pipework and the best type of emitters. Trouble is, for many installations, neither happens properly. Mainly because people are unwilling to pay. There are not many things in life that are worth paying a premium for, you don't really get better utility value from a BMW than you do from a Ford, but a properly designed heating system is one exception that you do. Now I am not saying that MCS installations are the premium system to go with, but at least, on paper, they have a system that covers the design aspect, even if it is not followed. How many people do we get on here in winter saying that their systems are not working, but when asked about heat loss calculations, they don't have a clue what we are talking about. Too many. Edited March 6, 2021 by SteamyTea Link to comment Share on other sites More sharing options...
OldSpot Posted March 6, 2021 Share Posted March 6, 2021 On 04/03/2021 at 18:47, RichardL said: Thanks Peter, Thats in my mind too - my numbers come out evens IF oil goes back to 50p (~36-40p now) and electric stays under 14p (~12-13p depending on tariff now) + I'd need to invest 5k after the RHI payback is taken into account. Even if RHI drops from my potential 10k to the 4k grant level over time the market should approach that 4k level - it will have to right or the market for renewable heat will stagnate. I'm sort of in that fear of missing out scenario, but I don't think it makes sense to rush in the next 12 months even with future subsidy likely to be less than current. I'm posting because I'm trying to double check my thinking. @RichardL That's what I did Richard and I concluded the same as you. Link to comment Share on other sites More sharing options...
J1mbo Posted March 7, 2021 Share Posted March 7, 2021 (edited) On 04/03/2021 at 13:46, RichardL said: Literally in two minds right now - the ASHP running costs vs. oil are not obviously cheaper - my installer thinks perhaps 20% saving, my back of the envelope calcs come out anywhere between evens and 15%, and that needs heating oil to go above 50p/Litre. Correct, and electricity is likely to continue to go up (it's basically doubled in the last decade) according to some EU study until 2025 at least. However, government will surely increase tax on heating oil in order to meet their CO2 targets and also electricity doesn't run out like a tank of oil. I would also say, anecdotally my house (with similar thermal load) is much more comfortable with the ASHP as I just leave it on all the time and have increased radiator sizes to allow for a lower temperature, and of course CO2 impact is reduced by probably 70% - depending on your location. Edited March 7, 2021 by J1mbo Link to comment Share on other sites More sharing options...
SteamyTea Posted March 7, 2021 Share Posted March 7, 2021 (edited) 8 hours ago, J1mbo said: Correct, and electricity is likely to continue to go up (it's basically doubled in the last decade) according to some EU study until 2025 at least. Or incorrect for the doubling bit in the last decade according to DUKES. UK domestic electricity has gone up 35.5% since 2010. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/904105/Electricity_since_1920.xls Edited March 7, 2021 by SteamyTea Link to comment Share on other sites More sharing options...
J1mbo Posted March 7, 2021 Share Posted March 7, 2021 Seems to vary where you look - the data here: https://www.statista.com/statistics/418126/electricity-prices-for-households-in-the-uk/ shows 13 to 22 but it’s in Euro cents so there is forex in the mix too I suppose. That site also has projection data which is worth a look. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 8, 2021 Share Posted March 8, 2021 (edited) 13 hours ago, J1mbo said: Seems to vary where you look Still not doubling in a decade. The ONS data is inflation adjusted. Edited March 8, 2021 by SteamyTea Link to comment Share on other sites More sharing options...
J1mbo Posted March 8, 2021 Share Posted March 8, 2021 That wasn't really my point , rather that electricity has gotten a lot more expensive and is likely to continue to do so for another 5 years according to the EU forecasts. It does depend on the window as it's volatile, according to table 211/212, CAGRs are: 4% from 1996 to 2020 - 1.5x each decade 8% from 2005 and 2019 - 2.15x each decade 5% from 2010 to 2020 - 1.6x each decade Link to comment Share on other sites More sharing options...
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