Based on ?average? gas and electricity costs (and ignoring for the moment other changes that might need to be made to a heating system for an air sourced heat-pump) which would be cheaper per kWhr?
I keep hearing folk extolling the virtues of heat-pumps but I was under the impression that gas was cheaper for equivalent output.
Tim
as ever "it varies", but poke some answers into
The electricity costs for a heatpump will be about 85% of the cost for mains gas,m but the installation costs are much higher.
You can now get £5k towards the cost of the heat pump.
You're better off getting the RHI, which "ought" to pay the install costs over a 7 year period plus or minus a grand, you can in fact have the £5k payment too (to save on upfront costs) but if you have both, they'll claw back the £5k.
Is that figure for ground sourced or air sourced heat pumps?
From my back of envelope previous investigations, an air sourced pump can give 3kW thermal energy for every 1kW of electricity but as the outside temperature falls to 0C this efficiency also drops to more like
2KW thermal per 1KW. As my electricity tariff is 4x that of my gas tariff it is debatable that air sourced in the UK can be cost effective. However all the green wash is not about saving money but saving the planet and in 2050 when all the oil, gas, coal and wood is banned you will have no choice.Installing an EFFECTIVE heat pump system also depends on the level of insulation in the home and probable there are large additional costs involved in changing components (radiators) on a water based CH system which may/will be running at lower water temperatures. Again the whole ethos of saving the planet is not about saving money but using less energy.
It may work extremely well for a new build where you can specify the quality of the build and insulation.
IIUC, the best CoP you will get out of a air sourced heat pump in winter is about 3, but only if you can cope with a low output temp of around 40 deg. If you need 60, then it will fall to about 2.
So in theory (downhill, wind behind it etc) you might be able to get 4kW (total) out for every 1kW in. Which in energy cost terms is probably comparable to gas. However I expect real world will be somewhat less convincing. Certainly worth doing if if your only choice is electric heating though.
ground source.
yes COP falls with temperature, but 1m below ground coils don't get as cold as air, unless coils are undersized and you end up freezing the ground by over-extracting.
as I said, poke some answers into the calculator.
Can still be marginal ...
This is backed up by very good article by Prof at Cardiff University ...... air to air heatpumps great in a bar or club where loads of people giving off heat ..... in a domestic environment not so good. His advice was if you have a water source then water to air much better fro efficiency or even ground source. He was also pretty scathing about reliability/longevity of pumps ...
And the most effective refridgerant gases have been made 'illegal' (AFAIK) and you need to also need to factor in possibly higher maintenance costs compared to a gas heating system.
Paul in Canada had quite a lot to say about this recently (heat pumps).
Something that people don't seem to be aware of (yet).
Neighbour in a 4-bed detached 1974 built house had an air-to-water Sanyo system installed. All the rads were replaced by triple-panel variety (8 of them).
They also have the 4KW solar panels on the roof (37 degree pitch, facing due south).
I asked 'er-indoors what it was like in winter, and she replied 'freezing'. So they have to burn logs etc on the fire (Class 1 chimney added by previous owner in the 1980's) to keep warm.
manufacturers claim zero maintenance costs for 7 years.
Is this for cooling the building rather than heating during the winter?
Assuming it is under your lawn, you might save some lawnmower energy usage!
The only person I have met that had one installed in domestic premises was bitterly disappointed with the running and servicing costs. In theory they should have been ideal customers being retired and at home all day but they were sold a pup. It cost more than fuel oil to do the same heating job (back when oil was still expensive pre-Covid).
Radiators all had to be replaced with big ugly things to cope with the lower working temperature so it wasn't a cheap or simple installation.
It needs the home very well insulated or your are burning money.
Air source can work except in the coldest weather but again unless the house is very well insulated it quickly gets expensive to run. I know someone with it who is quite happy - highly insulated new build.
I've heard one second-hand tale where the coils were undersized and it couldn't extract sufficient heat, still not sorted yet
I'm still trying to weigh-up whether to go for GSHP or LPG on a new build, it is quite touch and go.
We've got a large number of houses with ground and air. The air are not recommended, they are as expensive as using electric storage heaters and an immersion heater.
Ground, in theory, should be the way to go, if, you can get a good installer. 4 deep holes seems to be the best way of fitting it now, some of the ones we have only have one hole, and , of course, are nowhere near as efficient as those with more and deeper holes.
in merely cool weather a heat pump can achieve a 4:1 uplift which puts it at about 5p/KWh.
That's comparable in my case with oil at 50p/liter.
Well compare the figures above. I have no idea what gas costs.
And remember in the depths of winter even a 5KW heat pump at 2:1 uplift may not be enough...
Possibly their problem too. Look very carefully at ongoing maintenance costs too - that was their other major gripe.
If you can design it in as underfloor central heating and get the building insulation very very good then you might have a chance.
About a decade ago the Energy Saving Trust did a research project examining installs of heat pumps, then fairly new, and identifying issues. The reports are worth a read:
That was a decade ago. The government has some newer reports:
I imagine heat pumps have improved and the quality of installations likewise. I would be interested to know of any more recent research (rather than 'friend of a friend' anecdata).
Theo
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