Air source heat pumps vs. other options

[Bletchleyite]

From the EV thread: https://www.railforums.co.uk/thread...lectric-vehicles-is-realistic.231438/page-213

Mr Toad, I'm sure you're aware but many suppliers provide an overnight tariff, not just for the EV but the whole house. I pay 7p KW/h

That's Economy 7 and the likes which is based around using power when demand is low. With wider EV adoption it no longer would be, so it's likely that sort of scheme will fade into history. It's handy now though!

With that logic, why not just get a load of super-cheap resistive electric heaters then? You can get a 2-3kW heater for about a tenner if you buy in the summer and shop around...

Low capital outlay, but operating one single heater like that costs considerably more per hour than heating your whole house to a comfortable temperature with gas. They're a classic example of "it's expensive to be poor".

Yes, electric heaters are 100% efficient* but electricity costs much more per unit energy than gas. Hence why heat pumps are economic - if electricity was cheaper they wouldn't be.

* Give or take a tiny amount for a buzzing sound, a slight glow on the element or the little indicator LED. 99.9something% I guess.

And with thanks to Bald Rick and NIT100

Yes, I'm based in Northern Ireland so the domestic energy cap doesn't apply. NI is part of the All-Ireland electricity grid and there's a load of complex cross border legislation.
The upshot of it is that a) it's more expensive and b) there are none of the clever time dependant mechanisms available in the rest of the UK.

My options with PowerNI are:
Standard rate. 30.22p per KwH. No standing charge.
Economy 7. 35.17p per KwH (Day), 16.81p per KwH (1am to 8am) and 12p per day standing charge

Having worked it out, my daytime electrical requirements mean the Economy 7 tariff is more expensive.

Sadly, none of the suppliers like Octopus operate in NI. There are a few competitors to PowerNI but they all have pretty much the same prices. There are no smart or dynamic tariffs available - it's standard rate or Economy 7 regardless of who you contract with.
But even with this as the backdrop I am happy that we have one EV in the household. I can't do everything we need so I keep the old diesel estate but the EV does the shorter trips very well.

Yes, Economy 7 charges more for day usage. They always get their bit as it were

Ah, that's annoying Mr Toad!

I live in North Wales and we have the highest standing charges in GB.

I don't think standing charges to pay for infrastructure are unfair in and of themselves to be fair.

That's just ridiculous
Gas is 1/4 of the price of electricity so a lot cheaper even if it isn't as efficient

Heat pumps are £20,000 for an installation so very long payback period.
Or if it is bodged like a lot of installations, then they cost loads to run.

A Gas boiler is significantly cheaper and definitely cheaper to run than a heat pump

For now it is. Taxation on fossil fuels is likely to go up, whereas air source heat pumps will get a lot cheaper. Everyone already has a very cheap air source heat pump in their home - the fridge - so the technology isn't exactly new. There will come a point where they cost the same as gas.

Perhaps important to note that an air-source heat pump is something around 300-400% efficient. Meaning that all other things equal they cost broadly the same to run as a gas boiler (given gas cost around 1/4 electricity cost per kWh). But there is that not insignificant capital outlay.

Indeed, but they will get cheaper as the technology becomes more established.

 

[The exile]

For now it is. Taxation on fossil fuels is likely to go up, whereas air source heat pumps will get a lot cheaper. Everyone already has a very cheap air source heat pump in their home - the fridge

Indeed - presumably the cheapest and easiest economy that some people could make would be to bring the other one (the freezer) in from the garage or utility room and put it somewhere where the heat can actually be used.

 

[Bald Rick]

Indeed - presumably the cheapest and easiest economy that some people could make would be to bring the other one (the freezer) in from the garage or utility room and put it somewhere where the heat can actually be used.

I’ve often wondered if I should build a fridge and freezer sized opening in the kitchen wall, keep them outside in winter, with the cooling fins pointing inside, and vice versa in summer!

 

[SargeNpton]

Perhaps important to note that an air-source heat pump is something around 300-400% efficient. Meaning that all other things equal they cost broadly the same to run as a gas boiler (given gas cost around 1/4 electricity cost per kWh). But there is that not insignificant capital outlay.

Not sure that they can be any more than 100% efficient, by any measure.

 

[Bletchleyite]

Not sure that they can be any more than 100% efficient, by any measure.

Efficiency of a heating device is defined as the heat energy that is issued into the room from the device against the electrical energy used to power it.

Because a heat pump uses that electrical energy to bring in heat from elsewhere (i.e. outside) it means they are considered to be above 100% efficient, because they issue more heat energy into the room than the electrical energy consumed. The heat "pumped" in is not part of the calculation as it's not the thing you're having to pay for.

 

[JamesT]

Not sure that they can be any more than 100% efficient, by any measure.

It is when you're just measuring the electrical input. They're transferring energy rather than converting it. The other 200-300% is coming from the environment.

 

[Energy]

I reckon once the A2A (air-to-air) £2500 BUS grant kicks in will see a lot of installs of them.

A2W (air-to-water) can work great in homes (e.g. already managing a >= 45 degree flow temperature on existing radiators, or minimal upgrades), but the prices from the industry can be wild.

Heat Geek has some great content on A2W heat pumps, but their prices can be insane for even a basic no-pipe/radiator-changes install.

A2A's ugly indoor units is likely what would put most people off, but as they are more common, it should be less of a concern.

 

[Bletchleyite]

A2A's ugly indoor units is likely what would put most people off, but as they are more common, it should be less of a concern.

A2A of course is quite cheap as it's just an aircon unit that can run in reverse.

I'd not be concerned about the interior unit, I don't think they are ugly. Outdoors, by contrast, they're horrible looking things and totally ruin the look of a house. It's quite surprising little has been done to make them look nice.

 

[Harpers Tate]

Not sure that they can be any more than 100% efficient, by any measure.

As JamesT says: they use electricity not to make heat, but to pump refrigerant between an exterior heat-exchanger and the interior unit, extracting heat from the air outside and transferring it indoors. It's the same mechanism as used in fridges and freezers but applied "in reverse" - cooling the air outside and dispensing the heat inside by whatever means. Thus (say) 1 kW of electricity can extract up to (say) 4kW of heat from outside and redistribute it inside. So whereas a 100% efficient conventional heater has overall converted electricity to heat, a heat pump hasn't made much heat itself; rather it has moved it from where it's not wanted to where it is. That's how it can be considered ~400% efficient.

 

[AM9]

As JamesT says: they use electricity not to make heat, but to pump refrigerant between an exterior heat-exchanger and the interior unit, extracting heat from the air outside and transferring it indoors. It's the same mechanism as used in fridges and freezers but applied "in reverse" - cooling the air outside and dispensing the heat inside by whatever means. Thus (say) 1 kW of electricity can extract up to (say) 4kW of heat from outside and redistribute it inside. So whereas a 100% efficient conventional heater has overall converted electricity to heat, a heat pump hasn't made much heat itself; rather it has moved it from where it's not wanted to where it is. That's how it can be considered ~400% efficient.

... also a similar product of geothermal heating schemes, the pumps that bring subterranean hot water into the system use a fraction of the energy that the circulating hot water delivers into the heating system.

 

[Class 317]

I have had electric heating and hot water for the last 4 years in my 1 bed flat.

Their are many options for electric heating not just just pumps.

Electric storage radiators (Modern ones are quite a bit more efficient than the older versions).

Electric converter radiators that work like a normal radiator but use electric.

Electric boilers that work similar to storage radiators the brand that strings to mind is Tepeo or Fischer.

Infrared panel heaters that warm objects a d people rather than the air.

Electric infrared skirting boards.

I went for infrared with smart controls and the total installed capacity is 3KW.

In terms of the cost many people forget that gas central heating is not the efficiency marked on the boiler but how efficient heat is transferred from radiators into the room. Because of loses in pipework, mixing in valves, boilers not always being set optimally for maximum efficiency and poor controls most systems are at best around an average of 70% efficient.

Electric heating will be effectively 100% efficient.

When comparing costs don't forget that many electric systems require no servicing once installed and indeed some are DIY installs. Servicing a boiler costs circa £80 a year.

Also the gas standing charge works out about £125 a year.

So before you consider units costs you should assume say a circa 25% improvement of efficiency over gas, servicing costs and standing charges. Added up together at say 25p a KW you get circa 820KW of heat with electric heating before a gas boiler is even used. Add in the circa 25% efficiency improvement and for many smaller homes electric makes sense.

I pay £82 a month electric for hot water, heating etc.

 

[Bletchleyite]

Infrared is an interesting option. It heats the physical objects in the room (e.g. you) without heating the air other than that the air is heated by those objects.

I suspect for a well insulated one bed flat radiant electric is fine. If you get much bigger (or older) gas starts to tip the balance.

 

[najaB]

I suspect for a well insulated one bed flat radiant electric is fine. If you get much bigger (or older) gas starts to tip the balance.

That said, "well insulated" is the key to low costs, no matter the heat source.

 

[Bletchleyite]

That said, "well insulated" is the key to low costs, no matter the heat source.

Yes, true, if you go full-on Passivhaus then you need a tiny radiant input to keep it warm - a heat pump is just not worth it in those. Quite hard to get older houses to that standard though.

 

[Class 317]

Infrared is an interesting option. It heats the physical objects in the room (e.g. you) without heating the air other than that the air is heated by those objects.

I suspect for a well insulated one bed flat radiant electric is fine. If you get much bigger (or older) gas starts to tip the balance.

I'd have to disagree.

My flat is a north facing, ground floor EPC E flat. All I have done is have the windows repaired (rehung, seals replaced etc) which cost about £300, DIY draught proofing of the front door and draught proofing skirting boards etc.

It's actually heated the flat much more effective than the 6KW of electric convection radiators they replaced.

A well insulated 2 bed flat or 1 bed house should also be cost effective particularly down the south end of the UK.

 

[najaB]

Yes, true, if you go full-on Passivhaus then you need a tiny radiant input to keep it warm - a heat pump is just not worth it in those. Quite hard to get older houses to that standard though.

Agreed that Passivhaus standards will be next to impossible to achieve in a Victorian old build, but choosing between gas and electric before maximising insulation is comparable to choosing between different buckets to bail water from a leaky boat.

 

[Class 317]

That said, "well insulated" is the key to low costs, no matter the heat source.

I quite like the fabric light approach which emphasis on draught proofing, loft insulation, hot water pipe insulation but with a higher emphasis on smart controls, zoning etc rather than a whole house upgrade which for most will be unaffordable.

== Doublepost prevention - post automatically merged: 16 Mar 2026 ==

Another good use for a single electric heater is if you WFH and only need to heat the home office during working hours.

 

[najaB]

Another good use for a single electric heater is if you WFH and only need to heat the home office during working hours.

Indeed. Heating the spaces you spend the most time in, when you're actually using them, is more efficient than trying to keep the whole home the same temperature.

 

[GusB]

My housing association (HA) installed new heat pumps last year, replacing those that were installed around 10 years ago. The outdoor unit is far bigger than the previous one, while the indoor unit is now just a small flattish panel, replacing the one that was around the same size as a gas boiler. In that respect it's better, although I haven't really regained any usable space due to the original pipework being used; presumably it would be much tidier if the whole system was being installed from scratch.

I don't have a full year's figures yet, but looking at my January 2026 consumption compared to January 2025, I've used around 100kWh less electricity. Price-wise, my January bill was only about a fiver cheaper. Although it's not possible to do a direct comparison (I've since had solar panels installed and I've changed tariffs), I've certainly used the heating more this year. February's consumption was down by around 75kWh compared to last year. It'll be interesting to compare next year's numbers as I've now got new exterior doors and no longer have the same draughts when there's a howling northerly!

As the daylight hours increase, I'm now starting to see the benefit of the solar panels. Once the house is up to temperature, my baseline consumption is almost completely offset by the electricity that's being generated and in the middle of the day it's often negative. It's just a pity that I don't see the funds generated by exporting (the HA keeps this revenue), but I will certainly benefit from having significantly lower bills in all but the coldest months of the year and the cut in the unit price will also help.

 

[telstarbox]

The new Octopus Cosy ones look better - less like a traditional beige box.

 

[andrewgs]

There's also the option to use a battery, charge overnight and use resistive or infrared heating.
At current electric off peak rates of 8p/kWh and peak rates of 31p/kWh thats similar to a heat pump operating at a COP a little below 4 after battery losses.

The installation cost is lower (ignoring the grant) and you can load shift other electic use. For small homes/flats this seems a better option than a heat pump to me.

 

[Energy]

A good technology to look into is waste hot water heat recovery. They're just a heat exchanger between the cold water going into the shower mixer & the shower water going down the drain. They're extremely low maintenance and make electric showers much cheaper to operate.

Recoup.co.uk has a few units.

Infrared panel heaters that warm objects a d people rather than the air.

Electric infrared skirting boards.

I went for infrared with smart controls and the total installed capacity is 3KW.

Infrared is a good solution, but educating homeowners not to block the units is really important.

BBC News covered a good solution for embedding it in the ceiling a while ago; the company is iHelios.

 

[Harpo]

Indeed - presumably the cheapest and easiest economy that some people could make would be to bring the other one (the freezer) in from the garage or utility room and put it somewhere where the heat can actually be used.

The bigger economy would be to get rid of the freezer, especially if it’s an old unit. My 10 year old 900mm (width) fridge freezer was using almost 3kwh per day, around a third of my total consumption. It’s 600mm replacement uses <1kwh.

 

[najaB]

The bigger economy would be to get rid of the freezer, especially if it’s an old unit. My 10 year old 900mm (width) fridge freezer was using almost 3kwh per day, around a third of my total consumption. It’s 600mm replacement uses <1kwh.

Though, while it's a more efficient cooler, it's a less effective heater.

 

[yoyothehobo]

We took the opportunity to install an ASHP last year and undertake major renovations to the house such as underfloor insulation, underfloor heating which has made a huge difference. We have a solar diverter for the solar panels so we can heat water with excess power, especially good in the summer.

Our energy consumption is down significantly, however as the cost of electricity is higher than that of gas, we are only marginally down on actual costs.

 

[najaB]

We took the opportunity to install an ASHP last year and undertake major renovations to the house such as underfloor insulation, underfloor heating which has made a huge difference.

Wet system or electic?

 

[yoyothehobo]

Wet system or electic?

wet system, i think its called chip deck so it comes with grooves already in and pipes get installed within them, we put plywood above and laminate above that, rather than do anything with screeding etc..

 

[najaB]

wet system, i think its called chip deck so it comes with grooves already in and pipes get installed within them, we put plywood above and laminate above that, rather than do anything with screeding etc..

Nice. I installed thin-film electric underfloor heating in my last flat. We had to rewire anyway so it wasn't a huge lift to get the additional conduits installed for the thermostats. Made a huge difference compared to the storage heaters that it replaced.

 

[cb a1]

I got ASHP installed last summer. As noted by others, whilst only using a fraction of the energy that I used to heat the house with a gas boiler, the price per kWh for gas is a lot lower than the price per kWh for electricity.
I live in a 1950's built ground-floor flat. Apart from double-glazing, not aware of any other insulation. Energy Efficiency Rating when I bought it 3 years ago was band D.
I do love the operational aspect of the new system. House is lived in pretty much 24/7 and I have the temperature in the living room set to 19C with all the other radiators adjusted so other rooms are slightly cooler. Outside temp this winter got down to -7C and the system coped with that no problem.
Planning on getting solar and battery system this summer to reduce electricity cost yet further.
Paid for all this by taking 1/4 of my pension pot when I hit 55 a couple of years ago. Paid off the mortgage, installed the ASHP and will install Solar and Battery with what's left.
Aim is to get my fixed monthly outgoings as low as possible. Currently down to £355 pcm for Council Tax (10 months), electricity, mobile phone, TV licence and broadband. With some shopping around, and solar and battery, I'm hoping to get down to <£300 pcm by this time next year. Add in servicing and home insurance, and my fixed household costs will be <£4,000 p.a.

 

[osmarks]

Air-to-air heat pumps can also do cooling (or at least it requires some minor additional parts/changes), which is much more dignified than using fans or opening the window when it's warm.