Heat pumps work very well in cold weather. Air source heat pumps used in home heating systems will operate comfortably down to outdoor temperatures of -10C, much lower than we generally experience in the UK. In fact, heat pumps are used widely across northern Europe in countries such as Norway, where winter temperatures drop well below that.

One point to note is that lower outdoor temperatures affect the energy efficiency of heat pumps. On average, an air-to-water heat pump produces 4 units of heat for every 1 unit of electricity. This is known as a Coefficient of Performance (COP) of 4.  In colder weather, this may fall to 2.5 units of heat for every unit of electricity: a COP of 2.5. This still compares very favourably to a traditional gas boiler which has an average  COP of between 0.7 to 0.8.