The short answer: Yes, heat pumps work reliably in the cold, and in fact perform more efficiently than fossil fuel systems in temperatures as low as −30°C (not something you are likely to experience in the UK!).
Reading certain newspapers, you’d be worried about a future shivering at home as the government has forced you to install a heat pump that fails to keep you warm when the mercury dips below zero. There’s a lot of wailing and gnashing (chattering?!) of teeth, so we’re here to put your mind at ease. No, heat pumps are not a grand conspiracy to make your life worse and yes, they really do work in the cold.
We need to separate two concepts. The first is can your heat pump fundamentally, physically keep your home warm in very cold weather. The second is can it do it efficiently, i.e. does it need to use a lot of energy to do that.
Heat pump systems are sized to work at a “design temperature”, typically -2°C or -3°C in the UK. This means - if you have a skilled, capable installer - your system will work very, very comfortably and efficiently at this temperature.
What about when it’s colder than that? Yes, the system will still heat your home. It’s not suddenly going to stutter and stop, leaving you in a freezing home. It may need to work a little harder and use a bit more energy (the second concept we talked about - efficiency). At a certain point (think minus double-digits), your system may only be able to heat your home to say 18°C or 19°C instead of your regular 21°C set temperature. Not ideal, but you certainly won’t be freezing.
Still worried about what happens if the UK plunges to an icy -15°C? It’s entirely possible to design your heating system to work for that once-in-a-decade event, but you will be paying a premium for a capability you will rarely (if ever) need. As an alternative, a traditional solution such as an electric fan heater or an extra layer or two is likely to be a far more cost effective insurance policy than an oversized heating system with one day a decade in mind.
OK, but if my system is going to be less efficient in the cold, does that mean it’s going to use lots of electricity? Some boffins did a detailed study on heat pump performance and found that even when well below 0°C, heat pump efficiency is still significantly higher than boilers. The standard heat pumps they investigated were found to consistently outperform fossil fuel systems, remaining highly efficient during cold winters where temperatures fall as low as −10°C (i.e. the UK’s climate) and still outperforming fossil fuel efficiency down to −30°C.
This whole story is really a lot simpler than all that. Take a look at the chart below. You can see that many millions of people across Europe have chosen heat pumps for their homes. Indeed they are most popular in Scandinavia, famous for its freezing, snow-bound winters…
In 2020 there were 177 million heat pumps installed globally. It would be pretty strange if all these systems didn’t perform their single purpose - keeping homes warm - and people were still buying them in droves. In America, not exactly famous for its warm embrace of renewables and the climate protection agenda, more heat pumps were installed than gas boilers as far back as 2020.
You may not know it, but on the coldest of days you have almost certainly already been kept warm by heat pumps. Almost every bar, restaurant or shop you have been in will have been heated by a heat pump. If you find it hard to believe, just take a look at the picture below; a familiar scene on the back of many commercial buildings and down alleyways throughout the country. That’s right - those are heat pumps!
In short, the British media love a horror story (and an agenda): Google “Daily Mail” and “Heat Pump” together and you’ll see loads of articles about nightmare heat pump experiences. Nesta, a UK innovation agency for social good, did a detailed study and found that many homeowners who had switched to heat pumps preferred how they heated their homes.
We won’t pretend that there aren’t frustrated heat pump owners out there. There are issues with some installations (just like all home energy installations or complex technology - have you never had an issue with your boiler?). But where heat pumps are not keeping a home warm, it’s almost always because the system was not designed or installed correctly, rather than an issue with the underlying technology. That’s why it’s critical homeowners find a skilled, experienced installer for their heat pump, and have a robust guarantee that the installer will warrant their work and fix any issues that do potentially arise.