HOTTING UP: Short trips with air conditioning could waste fuel and offer little benefit
- Perry Richardson
- Aug 13
- 3 min read
Updated: Aug 17
With the UK preparing for its fourth heatwave of the year, motoring experts are warning that many drivers are using their car’s air conditioning in ways that waste fuel and offer little benefit on short journeys.
Specialists at LeaseLoco.com have explained that switching on air conditioning for quick trips is largely ineffective. The system needs time to circulate and cool the air inside the vehicle, and this process can take even longer if the car has been sitting in direct sunlight. On very short drives, the cabin often does not have time to reach a comfortable temperature before the engine is switched off.
Using air conditioning in these conditions can increase a vehicle’s fuel consumption by up to 10%. The additional load placed on the engine to power the system results in more fuel being burned. This is particularly noticeable in stop-start urban driving where journeys rarely reach higher speeds.
For trips at speeds below 40mph, the experts suggest rolling down the windows as a quicker and more efficient way to cool the interior. Opening the windows at low speeds has little impact on performance or fuel economy. However, at speeds above 40mph, open windows can cause increased aerodynamic drag, forcing the engine to work harder and reducing overall efficiency.
To help drivers get the best out of their air conditioning, the advice includes airing out the car before switching it on, starting the vehicle and driving before activating the system, and using the recirculation function so that cooler air already inside is reused rather than pulling in warmer outside air. Experts also recommend avoiding the maximum setting initially, as it is more efficient to start at a medium level and increase gradually if needed.
Keeping windows shut while the air conditioning is running is important to prevent cool air escaping, which would force the system to work harder. Parking in shaded areas or using a sunshade can also help maintain a lower interior temperature, making it quicker and easier for the air conditioning to work effectively.
With high temperatures expected to persist, drivers are being urged to adopt these practices to maintain comfort in the car while minimising unnecessary fuel use. By using air conditioning efficiently, motorists can help reduce running costs during the hot weather without compromising on cooler cabin conditions.
John Wilmot, CEO of LeaseLoco.com, said: “When you turn the AC on in your car it can take a while for the system to get going because it needs to make the refrigerant cold. This is the fluid that is used to cool the air.
“Once the fluid is cool, it’s then blown through the vents to cool the car down but replacing all of that warm air can take some time. It can take even longer if your car has been parked in the sun previously.
“This makes your car hotter and means the air conditioning has to work even harder in cooling the car down which is why it’s best to park in the sun or use sunshades.
“If you’re on a short journey and you're driving under 40mph, you’re actually better off just opening the window to cool down rather than waiting for the aircon to kick in. It’ll be much more efficient and you won’t be using any more fuel.
“If you’re driving in an area that exceeds 40mph then you’ll want to switch to using air conditioning. Driving at higher speeds with your windows open can create a drag which will make your engine work much harder and will ultimately cause your car to use more fuel.”
