To chill or not to chill: when to use a car’s air-conditioning in the winter

Once upon a time, air-conditioning in cars was the ultimate luxury, available only on the most expensive motors. Now it’s a standard feature in the most affordable cars on our roads: the small Dacia Sandero, Skoda Citigo and Vauxhall Viva city cars offer it. But drivers often think that it will be more economical and save on fuel if they don’t use it over winter, when the air rarely needs cooling. So the question is this: to chill or not to chill in winter?

Should you switch a car's air-conditioning off in winter?

Air-conditioning expert Sam Sihra from Alpinair, in West London, has been servicing cars’ air-conditioning systems since 1972. In his view, switching off a car’s air-conditioning system for weeks on end when the weather is cold, and perhaps only running it occasionally, is a mistake.

Why should drivers use air-con in winter weather?

Air-conditioning is the best way to dehumidify, or dry, damp air. With it running, the inside of a car’s windows won’t mist up; switch it off and it could seem as though you’re driving in dense fog. Equally, using the air-conditioning is a great way of de-misting the car if it steams up when you first get in it on a cold day.

Why else would it be wrong to switch off air-con in winter?

“Air-conditioning systems use refrigerant," says Sam Sihra, "and that carries a special oil that lubricates the compressor’s pistons or vanes. So if you leave it switched off for long periods, there’s a chance the compressor could seize.”

Sihra says modern cars are moving back to more reliable clutch mechanisms that switch off the compressor by closing circulation valves once that chilled air is no longer needed. Also, any rubber piping features seals, and those seals depend on the circulating refrigerant to keep them lubricated and prevent shrinking which causes leaks.

Air-conditioning not working? Check it for leaks before re-gassing

Gary Osgood from Avacs, Hampshire, explains: “Air-conditioning systems are essentially sealed systems and there shouldn’t be natural wastage as modern cars increasingly use as much metal pipework as possible. So if a system needs re-charging, it’s likely to have a leak.” His company has been tending to car air-conditioning systems for 17 years, and he says before drivers have their car’s system re-gassed, they should first have it pressure tested (using a special dye) to detect leaks – or it could be money down the drain.

How much does air-con affect fuel consumption?

Both Sihra and Osgood agree that running your car’s air-conditioning system is no more likely to reduce its fuel consumption than leaving a window open. That means a drop in mpg (miles per gallon) of approximately six per cent.

When a compressor can cost at least £1000 to replace, and helps keep windows free from condensation, you can see why drivers would be well advised to leave their car’s system running this winter.

When did air-conditioning first feature on cars?

The first model to feature a ventilation system that could cool the air coming into the cabin was a 1940 Packard in the USA. No surprises there: motorists in the super-size United States could routinely undertake road trips that make driving from John O’ Groats to Lands End seem like a stroll in the park. However, its cumbersome system got a frosty reception from drivers who baulked at the idea of spending more than $270, around 15-20 per cent of the entire car’s sticker price. Predictably, by the 1970s, as the price came down and more car makers refined the concept, air-conditioning had caught on like rock ‘n’ roll.

Read more: How to care for your car’s battery this winter