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How Much Does Aircon Really Affect Mileage?

Let’s set the scene. It’s a long family drive from Sydney to the Gold Coast for a family holiday. It’s sweltering. The seats are sticky with sweat. Everyone is annoyed and uncomfortable. It’s not the relaxing drive that the parents imagined, and not just because of the heat. The youngest has decided that their new fun game is to see how long they can annoy their older sibling for before they snap. The older sibling, now on a hairpin trigger due to the heat, is too easily baited and the back seat keeps devolving into screaming arguments, ‘they hit me’, ‘stop poking at me’, ‘I didn’t’, ‘you did’, ‘it was an accident’, ‘it was on purpose’, ‘you hit me for no reason’, ‘no I didn’t’.

The parents are growing more and more irritated, the front passenger routinely having to turn to admonish the kids fighting in the back, yet for some reason not one of them will admit to behaving badly, always blaming the other. The driver continually trying to avoid distraction from the heat and constant screaming. Knuckles turning white on the steering wheel as they wonder why they thought this was a good idea in the first place. The traditional Aussie vacation with the kids. (FYI, we previously wrote an article on car accessories to help avoid this situation, here.)

At some point the kids whine, ‘can we put on the aircon?’.

‘No, it uses too much fuel. Wind down the window.’

So, was it the right decision?…

Ha! Ha! No! It was a costly mistake! Let’s all take a moment to bask in the glow. Vindication!

The air-drag on that beat-up 80’s Toyota Celica, barreling down the Pacific Highway with it’s windows open would have increased fuel consumption far more than putting on the barely used aircon. In fact at most speeds running the aircon is far more efficient and has a far better cooling effect than letting air in continually. Using the aircon to cool the car can increase fuel consumption by about 8% – less than increased consumption from loss of aerodynamics.

Fun bit of trivia, driving with the windows open is about as inefficient as driving with a roof-rack.

What about on a cold day? Well opening the windows won’t do you any good, so there is only one variable, heater or no heater. So, it’s going to affect mileage.


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