Can air conditioning heat my home in winter?

Heating mode is not an afterthought bolted onto a cooler; it is the same refrigeration cycle run in reverse, harvesting heat from outside air and releasing it indoors. Modern units hold useful efficiency well below freezing, and London winters rarely test even their comfortable range.

The practical difference from radiators is speed and precision. A split heats the air directly and moves it, so a cold home office is comfortable in minutes rather than the half hour a radiator circuit takes, and you heat that one room rather than firing the boiler for the whole house. Shoulder seasons are where owners use it most: the October week before the heating goes on, the April cold snap after it goes off.

The efficiency story: a coefficient of performance around 3 to 4 means each kilowatt of electricity delivers three to four of heat. Against a plug-in electric heater that is a two-thirds saving. Against mains gas the comparison is tariff-dependent and roughly level, which still makes the split the cheapest way to heat one room without touching the boiler.

What it does not do: hot water, and whole-house radiator replacement is a different technology (air-to-water heat pumps, a different project entirely). Think of heating mode as making every cooled room cheaper to own: the same unit works twelve months a year instead of six weeks.

More in choosing a system, or browse all 40 questions on the FAQ index.