Modern air conditioning units are reversible air-to-air heat pumps, meaning the same system that cools your home in summer heats it efficiently in winter too. Rather than generating heat directly, the unit extracts existing heat from the outside air and moves it indoors, which is why it can produce several times more heat energy than the electricity it uses to run.

Under good conditions, a well-installed system can reach efficiencies of up to 400-450%, meaning for every unit of electricity used, several units of heat are delivered. Actual performance depends on the outside temperature and how well the system has been sized for the room, which is exactly why correct sizing is part of every job we do, not an optional extra.

This makes air conditioning a genuinely useful addition to a home’s heating as well as its cooling, particularly for a room like a garden office, extension or loft conversion that’s awkward to heat efficiently from the main system. If you’re looking at heating for the rest of the property, our central heating page covers radiators and underfloor heating.