Heat pumps are around 4 times as efficient as gas boilers. With low-carbon electricity, they will reduce our heating emissions close to zero.
Unlike the US, home heating systems in the UK are mainly gas boiler heated water distributed to radiators around the house. Thus, heat pumps would have to transfer the heat they generate into water (rather than air), which makes them more expensive. A household therefore may have to change their radiators to larger ones (as the heat pump cycle uses lower temperatures), as well as installing a new electrically heated domestic hot water system (as many houses have combi gas boilers). This is what makes installing heat pumps so expensive upfront in the UK
The solutions are, as you have said: larger grants, and electricity prices that are lower relative to gas. This would incentivize households to make the change. It will be interesting to see if the uptake in Scotland is higher than the rest of the UK, as the upfront cost there is, on average, no different to replacing a gas boiler.
Thanks for this. A note from a Brit living in the US. We live in western Washington State, where the climate is similar to the UK. We have a heat pump which works very well. Our electricity is very cheap here, about $ 0.12 per KWh, because of abundant hydro and a decent amount of wind power. For the first couple of years we were here, about 12 years ago, we never used it in air conditioning mode. Now, because of warner summers, we're using it for air conditioning most evenings in July and August.
As global warming continues to get worse, I imagine that the desire for air conditioning will drive heat pump installation in the UK.
Our house was built with a heat pump and central forced air. Houses in the US that don't have ductwork are still easy to retrofit as the walls are wood construction. These retrofits use minisplits - ductless units installed outside and through the wall, one per room. They can be set differently in different rooms and so are more efficient then whole house systems.
What is typically installed in the UK?
Interestingly I went through a similar purchase decision recently (for a electric water heater vs heat pump) and I could not make the numbers work out even with a 30% credit on installation cost plus a $500 credit from my utility.
As the manufacturers make both types of water heaters and they know of the federal credits, the water heater is quite marked up and the installers are the worst and I got quotes from several because heat pump water heaters are exotic so they charge a disproportionate mark up even though the labor costs are higher but not that much.
In my case gas is not available were I live and we already have a heatpump for cooling/heating so the heat pump boiler is just for water. Instead I got a programmable electrical water heater and just heat water when we need it instead of all day which I felt was a reasonable compromise
We do need to transition from gas boilers and I think hydrogen is a non-starter, for the lifecycle reasons mentioned.
I do feel, however, that focussing on replacement of gas boilers is misleading. The average UK home is draughty, poorly insulated and plain awkward. It has been a major issue to upgrade older coal fireplaces to GCH, usually a complete drains-up / interior rip-out, to route the wet pipes through walls, under floors and over ceilings, particularly in multiple occupancy homes. Replacing the rads with larger varieties and finding a space for heat pumps outside would be a challenge. In a typical London block, there might be five or six individual flats, each with a gas boiler. Routing new pipework from an ASHP to each flat would be prohibitive.
We need a complete re-think.
1) Insulate Insulate Insulate
2) Move to a model of apartment block / district level heating, one system feeding every flat. It works in Europe. The Chelsea pensioners (veterans) enjoyed the "waste heat" from Battersea power station for a hundred years, until someone decided to "upgrade".
3) We need all political parties to work together, thrash out an agreed approach, AND STICK TO IT past the next election cycle.
In the past few years we had the Green homes grant (scrapped before it was a year old).
Grants for installing EV charge points, scrapped.
Grants for EVs - Mr Schapps got his Tesla just before Mr Sunak scrapped that grant.
Cameron's government scrapped the home insulation scheme.
We had the Feed-In Tariff for domestic PV, so generous that private companies offered to fit the panels for free, in exchange for the FIT payment from "the government" - Scrapped
How are we supposed to plan for any work when the goalposts keep moving?
The Gov is "encouraging" us to have "Smart" meters. A condition for a discount on our PV installation. The meter is "smart" enough to read our usage and send it to Scottish Power but I have to visit the submit readings page every month to force it to create a bill - I was almost £2000 in credit until I discovered that trick.
We do get the "Smart Export Guarantee", a poor relation to the FIT. I pay about 32p per KWh for energy supply, they pay me 12p for every KWh I push into the grid. Every 6 months I have to sit at the "Smart meter" and wait for the display to move past "incoming" and go to "Export", write it down and then go to a different web page to submit the export reading.
I have two houses, both equipped with heat pumps from the beginning.
One is close to the sea, where it never freezes, it has an air heat pump for heating and cooling, which works fine. Hot water comes from an electric cylinder.
The other house has a continental location, with a few days down to -25 °C every winter, with a ground heat pump, which was supposed to also deliver hot water. Hot water never really worked. I added a third ground well, to no avail, and finally had to install a gas heater for hot water.
So, as they say, your mileage may vary ;-)
I think the thermodynamic efficiency benefit of heat pumps is well known, the real question is the economic efficiency vs other forms of renewable energy. For instance is it better to invest in solar panels and use simple and cheap resistive heating vs adding a heat pump? What is making this calculation harder is that solar energy costs and energy storage costs are rapidly falling vs heat pumps. In say 10 years we could have very cheap electricity most of the time which makes expensive energy efficiency devices like heat pumps not very desirable. I can imagine the outrage when people find they have been lumbered with a high cost heating system that never pays off. Maybe the best approach for a country like the UK is to wait and see what the energy market looks like after a few more years of solar deflation? Germany tried a similar approach of trying to rush a technology with solar panels a decade or so ago and ended up paying a lot of money for solar that is now much much cheaper, if they had waited a bit they would have saved a lot of money. The argument that government subsidies are needed so that an industry can get to scale seems weak to me, the UK is nowhere near big enough to do this.
I'm all in favour of heat pumps, but I have a number of comments. Firstly, I think the description of how heat pumps work is incorrect. I've never heard of them circulating gas in the house to heat it. The heat transfer would be very inefficient but, more importantly, the whole process depends on the liquid evaporating (by depressurising it) in the "warm" outside atmosphere. This results in a very cold gas, so it is able to absorb heat from outside. Clearly, it must be colder than the outdoor temperature for this to work and the efficiency of heat pumps drops off markedly at colder external temperatures. There must be a point below which they don't work at all. Heat pumps also circulate water at a lower temperature than gas central heating, so often larger radiators are needed, or the heating has to be on for longer. The cure for this is underfloor heating, which is probably only practicable in new dwellings.
I also think the comment about coolants is over-optimistic. It might be that leakage rates from a new, well maintained system is very low, but in the real world you have people using and servicing this equipment. You only have to look at how often car aircon systems have to be topped up to see the problem. On top of that, you get rogue manufacturers and disposal organisations who are careless. You only have to look at the several detections of breaches of the Montreal Protocol to see that ramping up production and use of HFCs and PFCs by 1000% is likely to cause significant problems, especially in a system when producers are almost entirely motivated by profits.
I don't know about gas power plants in the UK, but here in the US their average efficiency according to EIA is 44% (as of 2021). Factor in transmission losses and it's closer to 42%. Meanwhile most of us who burn gas use forced-air furnaces, not boilers. Many furnaces are above 90% efficiency, with some as high as 98%. On the other hand, even a gas furnace uses electricity, mostly for the blower motor.
Aside from these minor complications, I worry about a potential major complication: How do we know that heat pumps attain their rated COP in the real world? The one guy I know who actually measured his heat pump's COP got 1.7 (admittedly in a nonideal setting, cold weather and high altitude).
My understanding is that heat pumps don’t work too well in very cold climates...I live in Canada where winter is often -10 to -30 Celsius. Secondly, as you mentioned Canada is a lower Carbon electricity producer with a lot of hydro and nuclear energy with little coal at around 6 percent
Hannah, would you like to write an article about the future supply of electricity, assuming we transition to electric cars and electric heating. We need to figure out how to generate and distribute this. And we need other sources (eg nuclear) to supply electricity when renewables (wind) aren't working.
Interesting article but sadly has missed some of the key issues with heat pumps:
1 80% of UK households have central heating with water filled radiators that are designed for a water temperature of 65°C. Heat pumps cannot supply water at this temperature, only 40°C and at this low temperature the radiators will not output enough heat to warm the house.
2 56% of homes in England have an EPC efficiency rating below C, meaning that they are unlikely to be able to be heated by a heat pump because of the low heat output. Typical domestic heat pumps only output 5 to 7 KW compared to the average gas boiler of 12 to 15KW. Also heat pump output ( and efficiency) gets lower as the outside temperature drops in winter.
Heat pumps are not 4 times as efficient as gas boilers. In fact heat pumps do not save energy when considering the whole life cycle.
I looked into this for my house, built in 2001. I was told that it would mean replacing all the radiators and pipes i.e. a major refit throughout the house, pulling up floorboards etc – not only very expensive but hugely disruptive. So, sadly, I’m looking at other options. Storage heaters, anyone?
PS The UK electricity grid will need a huge overhaul and increase in capacity as we move from fossil fuels to 100% electric power. I don’t see that happening yet.
Checking in from Aotearoa New Zealand, where 25% - 40% of households are heated by heat pump. They’re amazing.
I installed a heat pump for a small backyard building and I love it. I did compare it to a natural gas furnace (~92% efficient) pretty carefully, however, for my energy utility and got much different conclusions than you found in this article (comparing to a gas boiler). I estimated the heat pump is about 30% more expensive and has a 15% higher carbon footprint (based on the utilities overall carbon / kwh number). Of course this will improve as the utility moves away from coal (currently about 50%). But I thought it was interesting (and a bit disappointing). I was surprised that the pricing for electricity is so much higher than natural gas to make it more expensive to run the heat pump, because like you say, heat pumps are very efficient. I used 300% for my air-to-air heat pump.
I have a dual-fuel packaged rooftop unit with both heat pump and furnace from Trane. The only inverter-driven, all-electric, packaged or ducted unit that I know of is offered by Bosch. Does anybody know of any others?