Do heat pumps work in winter?

It is the question we hear more than any other in Forest Row: a heat pump sounds fine in spring, but will it keep me warm in January? Here is the plain answer first, then the detail for anyone who likes it.

The short answer: yes

A well-installed heat pump in a reasonably insulated home will keep you warm and comfortable right through a Sussex winter, including the cold snaps. Performance does dip a little when it is freezing, as you would expect, but a properly designed system is built with that in mind and keeps a comfortable margin. The two things that decide how well it works are the quality of the installation and how well your home holds its heat.

How it works, in plain terms

A heat pump does not burn anything. It uses electricity to move warmth from the outside air into your home, a bit like a fridge working in reverse. There is usable heat in outdoor air even when it feels cold to us, well below freezing, and the heat pump gathers it and lifts it to a temperature that warms your radiators and hot water. Because it is moving heat rather than making it from scratch, it gives out more energy as warmth than it takes in as electricity. That is the whole trick, and it is why a heat pump can be cheaper to run than you might expect.

If you like the detail: the numbers

The efficiency of a heat pump is described by its Seasonal Coefficient of Performance, which is simply how many units of heat it produces for each unit of electricity it uses across a year. A figure of 4 means four units of heat for every one of electricity.

The reassuring part is that this is measured, not just promised. Across 252 independently monitored UK homes, the average Seasonal Coefficient of Performance came out at about 3.87, close to four to one (Open Energy Monitor (https://openenergymonitor.org/)). The best-designed systems reach 4.5 and above. And on a cold winter day at around minus 2 Celsius, well-installed systems in a twelve-month study still delivered about three units of heat for each unit of electricity, exactly when you need it most. For comparison, a modern gas boiler runs at an efficiency of roughly 0.85 to 0.93, so it always gives out less heat than the energy in the fuel it burns.

The pros and cons

• Pros: High efficiency across the year, useful heat even in freezing weather, no fuel deliveries, and lower exposure to gas price swings. A grant of £7,500 is available through the Boiler Upgrade Scheme for an eligible installation by a Microgeneration Certification Scheme certified installer.

• Cons: Performance depends heavily on a good design and a reasonably insulated home. A poorly sized or rushed installation will underperform, which is why the survey and the installer matter as much as the unit itself. Radiators may need upsizing in some rooms.

What this means for Forest Row

Many homes here are older and off the gas grid, so two things decide whether a heat pump works well: the fabric of the home, and the quality of the installation. Fabric first is not a slogan, it is the cheapest way to get a great result. Insulation and draught-proofing reduce the heat your home needs, which lets a smaller, lower-cost heat pump run at its most efficient. Get those right and a cold Sussex morning is no problem.

If you would like to talk it through, you can now meet us in person at our community energy drop-in at Forest Row Community Centre, alongside the Repair Cafe (dates on our website). You are also welcome to a free suitability pre-check: browse our audited local suppliers (https://www.forestrowenergy.com/local-suppliers), see what support might suit your home on our grants page (https://www.forestrowenergy.com/grants), or send a quote you have received to our quotes and bills review (https://www.forestrowenergy.com/quotes-bills-review). It is also worth knowing your home's current Energy Performance Certificate rating, as it is a useful starting point for planning insulation first.