Just listening to R4 Today and there was discussion about the targets to get all new ICE-only engine cars stopped from 2030 and there was also a discussion about ground source pumps replacing gas boilers in the home.
I like to be green where I can and have been thinking about this more and more lately but aside from the environmental thing, is this one of those investments (like solar) which pays back over a huge length of time? We are likely to move out of our home in 6-8 years so would we end up losing money? Would it increase the house value? Are they any good? Can they sufficiently heat a home of four plus provide hot water? Are they easy to fit and do they provide proper hot water, as a boiler would?
The final thing is cost; I have looked online and they appear to be £10k plus for the units themselves so I guess you could add a few £k to fit too. Is this correct? Are there subsidies as a chunk of cash of that scale isn't readily available?
Have a browse through the link below. I found the replies very helpful when I asked. Good discussion on the future and battery power being the main stay in the world
Thanks. I'd missed that completely
We have a GSHP run by green electricty, so for heating and water we are close to carbon neutral. The thing run without a flaw for close to 20 years now, with a service every couple of years or so.
Cost wise it has certainly recovered the extra investment.
As I understand it, the main problem with replacing a gas boiler with a heat pump is that the hot water produced is not as hot. This means that either you need to replace all of your radiators with substantially larger radiators or you need to install underfloor heating. Neither of these would be a cheap option.
Another concern I have regarding ASHPs specifically is noise pollution - with an external unit on every home I'd expect a fair bit of background noise, especially where fans start failing and people don't fix them.
> As I understand it, the main problem with replacing a gas boiler with a heat pump is that the hot water produced is not as hot. This means that either you need to replace all of your radiators with substantially larger radiators or you need to install underfloor heating. Neither of these would be a cheap option.
No. And wouldn't be practical for me either.
I have an ASHP and it is fantastic. Complete central heating installation in a no mains gas village in a house with no wet heating (coal fire + storage heaters when we bought it). Whole installation has paid back in under 6 years.
But I read a lot of bad stories about ASHP, so I think it comes down the lack of knowledge in some installers. To get RHI payments I think many have been installing them on the cheap. To work well you need to insulate house well, install oversized radiators and run the system in the 30 - 40 degree range.
I heat 2 story house with footprint of 100m2 for ~£600/year. My additional electricity use is £400 for hot water, cooking, etc. I get £600 back from power I generate.
How noisy is the external unit on yours? When scaled up to a large housing estate, would it potentially be quite unpleasant? Aircon units often aren't silent, and it's basically an aircon unit operating in reverse, isn't it?
By the way my gas bill for a smallish 3 bed house is £360/year (newish condenser combi boiler, but it wasn't much different with the old one) - no idea what the footprint is, though. Any method of heating (other than electric radiant) will be cheap if your property is well insulated.
Practicality and payback time does depend on the type of house. We had a quote for our house, built in 1860, stone walls, high ceilings, poor insulation (and little room to improve). We needed two of the pump units to generate enough heat, and even then there were concerns about whether they would actually produce enough heat to keep us warm. We ended up going for an oil boiler.
We also have an annex, similar construction but much smaller rooms and better insulated. Just got a quote for heating with ASHP so we can get rid of the current, very expensive to run, electric heaters and take advantage of the GHG. This looks feasible, just sorting out some detail but think we're going to go with it.
Oil would have been £1500 / year in 2014 based on similar property sizes. My previous house (3 bedroom) was 1/3 the footprint (just multiply the width of your house by the depth).
I picked the lowest noise unit (Nibe) and we cannot hear it in the house, and externally in winter it's probably about the same noise as next door's external oil boiler. GSHP would be quieter and I'm considering switching when I do a major extension and alteration.
> As I understand it, the main problem with replacing a gas boiler with a heat pump is that the hot water produced is not as hot. This means that either you need to replace all of your radiators with substantially larger radiators or you need to install underfloor heating.
Whilst not disagreeing with what you say, I wonder if a different pattern of use somewhat mitigates those shortcomings. Instead of gas’s on demand operation a background continual operation may be enough i.e. whilst you are out of the house or asleep the heat goes to a storage tank for hot water.
My house was built in 1890’s (and mains gas finally arrived in about 2000), currently one bedroom has no ceiling or door, the dogs like having an outside door open and my main form of heating is a stove burning anthracite and coke. It has a thermostat that goes from 0 to 5. At this time of year it is set on just below 0.5 (basically just ticking over on a bucket of coal every other day) and my house is warm enough despite the water in the CH being between 35-40C. Admittedly having the stove located in the middle of the house help massively.
As can be seen from the graph at night the heat goes to the tank, calculating temp rise/time gives a result of about 400W so a bit different from my 3 year old 28KW gas boiler that heats the water to 65C.
I am concerned about the noise pollution caused by all those heat pumps running 24/7 but I suppose in time fan design will improve.
The concern is less about whether you can hear it in the house (you can also hear a gas boiler to some extent, sound from the pump and moving water usually echoes around the radiators and pipework), it's about noise nuisance to others, particularly if on overnight.
I've got 12yrs experience of commercial installations, not domestic. We don't use 'payback', but rather investment tools like Internal rate of return etc. In general our experience has been (repeat commercial setting) that maintenance & component life-cycle costs is higher than modelled and energy savings accurate. I.e. the pumps need replacement more often than we hoped, but the energy consumption accurate.
Certainly you'd want to use underfloor heating at ground floor level to get the best from the system. Overhead radiant panels are awful - don't go near them in a domestic setting.
As an investment I'd suggest it's marginal unless boilers/ rads etc needed replacement anyway, or the cost of gas goes through the roof. (NB domestic electricity costs are due to increase substantially over the next few years - currently the average annual elec bills has a subsidy element of £85 or so at the moment, due to increase to £200 with existing CFD type commitments - I'd eke out the gas boiler for now!).
ASHP are going into all new commerical developments these days. Definitely the wya forward until or if Hydrogen kicks off.
- Around 350% efficiency
- Benefit from future electrical grid decarbonisation
- Benefits from government RHI scheme
- Lower Flow temperature (biggers rads potentially)
- Need storage cylinder (with heating coil)
- "Complicated" if they break
I'd definitely go for it myself
> The final thing is cost; I have looked online and they appear to be £10k plus for the units themselves so I guess you could add a few £k to fit too. Is this correct? Are there subsidies as a chunk of cash of that scale isn't readily available?
We've recently got a quote for 11k for the ASHP plus all the work involved. This is for a 12kW heat pump.
You can apply for the Green Homes Grant to pay for some of this cost and/or the RHI that pays you a return as you use the heat pump. See https://www.gov.uk/guidance/apply-for-the-green-homes-grant-scheme
So the thing about any form of heat pump - air, ground or water source - is that the efficiency is linked to the change of temperature it is trying to effect. Going from, say, air at 7 degrees to water at 35 degrees is a small jump and you will get efficiencies in the region of 450% (or a CoP of 4.5). Water at 35 degrees is perfect for underfloor heating, and acceptable for big radiators, but pretty much useless for normal size rads. A rad that would be giving out 1000W with water at 70 degrees being pumped through will be giving out much much less power with 35 degree water. Even running it 24/7 will still not heat your house up.
You can ask most heat pumps to do bigger heat differentials. You can get it to do A7W55, but the efficiency will be much lower - around 280%. This is what's going on when you use it to heat your domestic hot water tank.
As the outside air temp drops, do does the efficiency, and the problem is that this is just when you ask it to do the most work in heating! With an outside temp of -3, getting water at 35 degrees to run your oversize rads or UFH is still ok (efficiency will be in the 150%-ish region) but if you try to get water up to 55 degrees to runs regular rads then the efficiency is going to be 100% or even less.
The RHI calculator knows this, and basically won't pay out if you don't have rads big enough.
> my main form of heating is a stove burning anthracite and coke.
> I am concerned about the noise pollution caused by all those heat pumps running 24/7
Ha ha ha. Man burns coal and worries about other people's hypothetical noise pollution.
> Ha ha ha. Man burns coal and worries about other people's hypothetical noise pollution.
The noise pollution is real, not hypothetical, especially with older ASHPs. There is one five or so houses down the street from my parents house, and I can hear it every night I stay in my old bedroom. Good thing it was installed after I left, otherwise I would have long committed murder!
We have recently built an extension above our garage, and my bedroom is now in there.
I keep getting woken up by a boiler turning on in the morning - spent ages trying to understand why our boiler wa son when it should have been switched off - has only taken my 2 months to realise its next doors! (Oil still).
I see a few companies do ASHP which can integrate with existing combi boliers - and 'play the market' using electricity when the ASHP wil be the most efficient solution and the gas when that works out best - quite attracted as nice to have a couple of options.
I just had a quote from a local certified installer. They want upward of £14K to install a 16kw Mono ASHP and upgrade the HW Tank and 4 radiators. the numbers quoted here for efficiency seem to be contradicted by the model that the installer gave me. They predict 16000 KwH cost to provide 24000KwH of heat. So why is it that people claim such large efficiencies. 150% is what the model gives. But its the £14K that puts me off. Grant of £5K installation and 6 years of £880 RHI means the installer wants it all and more. The expectation if the 150% efficiency is true then the electric is going to cost the same as my gas bill so no ongoing RHI or utility bill savings. I find myself disappointed.
Could you post a link to the model that was suggested by the manufacturer? Something doesn't seem quite right if they are quoting at efficiency of only 150% and I would just be interested to see thew model.
Also, if even the best ASHPs will struggle to compete on running cost with gas as electricity (approx 15 p/kwh) costs around 4 to 5 times more than gas (approx 3-4 p/kwh) but you would only achieve an efficiency in that region in absolutely optimal conditions
I have pm'd you a onedrive link. lets hope you find something more positive. The estimation of my current gas is over -the -top by about a factor of 2.
> Could you post a link to the model that was suggested by the manufacturer? Something doesn't seem quite right if they are quoting at efficiency of only 150% and I would just be interested to see thew model.
> Also, if even the best ASHPs will struggle to compete on running cost with gas as electricity (approx 15 p/kwh) costs around 4 to 5 times more than gas (approx 3-4 p/kwh) but you would only achieve an efficiency in that region in absolutely optimal conditions
They might just be being honest! Typically a COP of 3 is okay for the plant but built into a house with real people living in it things look different.
There's a literature meta-study on real-life efficiency on Science Direct (Air Source Heat Pumps field studies: A systematic literature review) and they are talking for the UK of values as low as 1.2 and an average of 2.2 which my mad tech buddy who has an ASHP system would agree with for the normal user in a retrofit. Like always it's the problem of people not understanding it's central heating, not warmth on demand and the increased comfort levels as it's cheaper.
The problem as you know in the UK is insulation. Most houses just aren't, or at least nothing more than a token gesture. You really need a porch, veranda, vestibule on any outside door so you can have an air lock system entering the house and avoid a massive surge of cold air coming in. Especially in a busy family house with folk coming in and out frequently.
On the noise side. I could sleep 2m away from the internal blower and not notice it, if the house is insulated you should not hear the outside unit at all!
We insulated all walls with a minimum of 100mm, some insulated both sides to avoid bridging, there is a slight loss of interior space but you gain warmth. 400mm in the loft. Then put in Panasonic units, one up and one downstairs operating independently, cost about £4000 fitted.
thanks Steve, you are right the model predicts 377% efficiency. I still can't understand how one pump, 4 radiators and 1 HW cylinder can add up to £14K. They are having a laugh!
I would suggest that at this early stage in the use of the technology many adopters are wealthy people acting from benign motives who are not too worried about cost. Maybe the installer is assuming that. Get a couple more quotes.
Are they going to have to do some re-wiring as 16kW will draw a fair bit of current?
> Are they going to have to do some re-wiring as 16kW will draw a fair bit of current?
Apparently not. They would need to convert to three phase supply if the electrical supply is insufficient. 10m of 7mm cable will suffice I think. The company response is that the high cost is due to onerous requirements of accreditation to the government scheme. That is a circular argument though that means they are not heating engineers, rather they are government grant consumers and I am their the conduit to the motherload..
That'll be 16kW heat output, not electricity input.
I'm 99% sure that the 16kW refers to the heat output and not the electrical requirement of the unit. Unclear exactly what the maximum electrical input requirements would be but 7kW seems plausible. Coincidentally, 7kW is the same power requirement as most home chargers for electric cars and there is a nice long thread already on what this means for the wiring to houses. It's possible that the answer is that you can charge your car or heat your house, but not both simultaneously.
>Coincidentally, 7kW is the same power requirement as most home chargers for electric cars and there is a nice long thread already on what this means for the wiring to houses. It's possible that the answer is that you can charge your car or heat your house, but not both simultaneously.
Pretty unlikely. 14kW is about 60A, and generally houses have 100A main breakers.
If you do get a really powerful EV charger (I charge at 2kW) and a big ASHP, then it's just possible that in midwinter when the CoP is lowest, you can't run both devices at the same time as making a cup of tea and some toast whilst doing the ironing.
A typical 16kw nominal output ASHP like a Samsung is drawing 17A when it's in optimum conditions BUT if the air outside is too cold they run an internal electric heating system to keep the output up so the max current rating (and the circuit breaker) is 32A.
So under optimum operation, to give 16kW is a draw of around 4kW (ie CoP of 4) and worst case is around 7.4kW (CoP 2.1)? Sounds about right. I've heard of pumps getting close to CoP 1 in really adverse conditions (trying to heat water to 65 degrees with air significantly below zero).
That suggests this 12kW pump might draw 5.5kW at most.
Perhaps a slight repeat of others, but.... Air source is far more prevalent than ground source, due to the simplicity of install and repair.
You’re probably looking at a min of £12k for supply and install.
They are often common in areas that do not have a gas supply. Gas boiler is far cheaper due to sheer market volume and economy of scale for install and repair.
You can get a good gas combi boiler for a few grand, and it will be cheaper to run than a heat pump, due to higher heat pump electrical costs, particularly if SOP is poorer. But this is why people in rural areas without gas access go for a heat pump as an alternative to oil or electric heating.
If you can pay the up front costs for a heat pump you can claim the Domestic RHI to claw back the extra investment. The whole point of the scheme is to bridge this financial gap and push renewables. They are accepting applications till early 2022. Quarterly payments for seven years. You could potentially recoup the lion’s share of the cost of your install.
RHI payments are NORMALLY based on the deemed heat demand for your property, as stated on your house’s Energy Performance Certificate. Check this, then visit the BEIS website and use their RHI payments calculator.
The scheme does dictate that if your EPC recommends loft or cavity wall insulation, you’ll need to have this fitted in order to be eligible (unless you meet exemption criteria). If required, you need to fit it, then pay for an new EPC- all prior to applying for RHI. This is a big consideration when weighing up cost, so the EPC is the starting point when considering an ASHP funded using RHI payments.
Any funding from the Green Home Grant is deducted from RHI entitlement.
Another thing to consider is that a lot of small heat pump installers go bust, leaving customers struggling to find an alternative company for service and repair. This will probably only get worse with the current COVID economy.
MCS website is a good source of info too.
thanks, a good summary of the problems. You are certainly right that heat pumps are expensive and the firms go out of business. The same happened to my solar panel installers, they went out of business with the government withdrew is support. However the grant for them was much more generous so I'll be receiving generation payments for 25 years. That goes someway to compensate me for the constant cold calls from companies offering to service them. The ASHP grant seems to end after 7 years, which I suspect is the point when it'll need replacing or at least regular repairs. that isn't very appealing.
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