We grumble about the air-conditioning bill all summer, but rarely ask the opposite question: does cooling a home actually cost more than heating it? In most homes the answer turns the assumption on its head: keeping cool in summer costs less, and pollutes less, than staying warm in winter. Two factors explain it, and hardly anyone stops to think about either.
What matters is the temperature gap, not the heat
What it costs to keep a home comfortable depends mainly on how far the system has to pull the indoor temperature away from the outdoor one. In summer, taking a house from 30C down to 24C is a gap of around 6 degrees. In winter, warming it from 4C up to 20C is a gap of 16. Heating has to bridge a temperature difference more than twice as large, for far more hours a day and far more weeks of the year. The British heating season lasts for months, while the days when you genuinely need cooling add up to a few weeks. That is why heating dominates the average home's energy use, and cooling barely registers by comparison.
The hidden advantage: moving heat, not making it
A second factor matters even more. An air conditioner or a heat pump does not create cold or heat from nothing: it moves heat from one place to another. For every kilowatt-hour of electricity it uses, it shifts three or four kilowatt-hours of heat. A gas boiler, by contrast, burns fuel and always delivers slightly less energy than the gas contained, so cooling with electricity is often more efficient than heating by burning. Then there is the environmental angle. Britain's electricity increasingly comes from renewables, while gas remains a fossil fuel that emits carbon dioxide every time it is burned. To run your own numbers, start with electricity prices and our air conditioning guide.
What this means for your bills
A quick example shows the scale. Run an efficient unit to cool the living room on summer evenings and the whole season will cost you tens of pounds. Heat the same home through a full winter, on gas or a heat pump, and the bill easily runs into the hundreds. Cooling is not negligible, but the bulk of what a household spends on keeping comfortable still goes out in winter.
None of this makes air conditioning free; it simply puts the cost in perspective. An efficient system set to sensible temperatures, in a well-insulated home, adds far less to the bill than winter heating does. And it works both ways: the same habits that keep heat in during winter keep it out in summer, with blinds and shutters down and windows shut through the sunniest hours. The real summer waste is not switching the cooling on, but running it at 20C with the windows open. The tips in our guide on how to save electricity work just as well right now, only in reverse.