Date Published: 14/01/2026
The science behind why warming up your car during the Spanish winter doesn’t hit your wallet
According to the experts, avoiding using the heater in winter in order to save fuel is “completely foolish.” That’s because there’s a big difference between how your car generates cool and hot air, explains mechanic Juan José.
Air conditioning really does use more fuel because the air con system has a compressor that is powered by the engine. When it’s switched on, the engine has to work a bit harder to run that compressor, and that extra work means extra fuel is burned.
“Air conditioning has a kind of compressor that moves through the engine, therefore, the engine itself has extra consumption which it has to compensate for with more energy from fuel… but heating does not,” he explained.
Heating works in a completely different way. In most cars, the heater does not burn extra fuel at all. It uses heat that the engine is already producing anyway.
When your engine is running, it gets very hot. To stop it overheating, coolant water circulates through the engine and then through a radiator to cool it down. The heating system simply diverts some of that already hot water through a small radiator inside the dashboard. Air is blown over it and into the cabin, which is why warm air only really comes through once the engine has warmed up.
Because the heat is basically recycled waste heat from the engine, turning on the heater doesn’t make the engine burn more fuel. You are just using heat that would otherwise be lost.
On his TikTok Spain channel, Juan José also mentions that some modern cars have electric heaters or electric radiators, especially hybrids or newer models. These use electricity rather than fuel. Even then, the impact on fuel use is tiny and usually only noticeable right at the start of a journey.
The mechanic’s final message to drivers is simple: if you’re cold, blast that heating. Cold air uses more fuel, but hot air definitely does not.
Image: Freepik
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