Your air con is a heat pump
An air conditioner doesn't create heat or cold: it moves heat from one place to another. Reverse the direction and the same unit that cooled your bedroom in summer efficiently warms your living room in winter. That single fact is what makes the economics work.
AC heating vs gas central heating
- Efficiency. A brand-new gas boiler is about 90% efficient. An air conditioner has a Seasonal Coefficient of Performance (SCOP) of 3 to 4, meaning it's effectively 300% to 400% efficient. It outputs 3 to 4 units of heat for every 1 unit of electricity it uses.
- Running costs. Electricity currently costs more per unit than gas in the UK (roughly 26p vs 7p), but the heat pump's huge efficiency advantage closes the gap. Heating the one room you're actually sitting in with an AC unit is highly competitive with firing up a whole-house gas boiler.
Pairing it with solar
If you have solar panels, the economics become genuinely compelling. Your peak demand for cooling (hot, sunny summer afternoons) lines up almost perfectly with your peak solar generation. Running the AC during the day in summer is effectively free.
And in the "shoulder seasons" of spring and autumn, your panels can power the AC to heat your home during the day, letting you leave the expensive gas boiler switched off for months at a time.
One system, both jobs
That's the case in a sentence: a single, quiet, filtered system that cools you through the heatwaves and heats you efficiently through the winter. For more on comfort and health, see the health & sleep guide; for the summer cost breakdown, see what it really costs to run; and for why the summer half of the job keeps getting harder, see how Welsh summers are changing.