Should I use A/C or open my windows?

Written by: Simon Pavey, Last updated:27th February 2023

Air condition on car dashboard with graphics indicating cold air blowing

It’s a common question when you’re behind the wheel on a hot day and you need to cool down: should you switch on the air conditioning or just wind the window down?

Granted, it’s not the most important decision you’ll ever have to make regarding your car, but it’s always worth being fully informed so you can make the right call to boost fuel efficiency and maintain the health of your car.

Benefits of using air-con throughout the year

There are some significant benefits to using your air-con regularly over the course of the year, as consistent use reduces the risk of the system seizing up and stops circulation from deteriorating.

Refrigerant and oil are required to make the A/C in your car work, so it’s a good idea to switch it on regularly to keep the liquid flowing and the components of the system lubricated.

During the winter, switching on the A/C to generate warm air is a good way to clear misty windows, since the air coming out of the vents is dry and acts as a dehumidifier.

Should I have the window open?

When you’re driving in hot weather, your first thought might be to open the windows, but if you have the air-con running at the same time, open windows could make it harder to cool the car down.

Having the A/C on and windows open isn’t particularly economical. Running the air-con puts additional strain on the engine, which consumes fuel, but an open window eliminates the effect by allowing the cool air to escape and letting in warm air from outside.

A handy rule of thumb is that if it’s hotter and more humid outside the car than inside, running the air-con will be more effective if you keep the windows closed.


Fuel efficiency is another factor you might want to consider when deciding between switching on the A/C or opening the window.

Both options impact your fuel consumption in some way. Opening windows means there is more drag on the car, which slows it down and means the engine has to work harder, using more fuel. Air-con also places a demand on the engine and increases your fuel consumption.

Back in 2004, General Motors conducted a number of surveys to find out which is the more fuel efficient option. The results suggested that having your windows down and the air-con off is probably more economical.

In really hot weather, however, you might not get the same cooling benefits from outside air as you do from your car’s A/C system.

Like all vehicle components, air-con needs to be checked and monitored to keep it healthy. Getting the system re-gassed is often the best way to improve performance.

Regular servicing and maintenance is vital to ensure your car is always safe, comfortable and reliable. MyService.Expert from Fuel Card Services makes it easy to look after your car with access to thousands of garages all over the UK.