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How Much Does my Car's Air Con Cost to Run?

How Much Does my Car's Air Con Cost to Run?

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Many of us worry that turning our car's air con will drink fuel, but is this true? Motoring journalist, John Swift investigates if this is true and how you can use your air con more efficiently.

The do's and don't of using your car's air con

  • Don’t be tempted to turn the vents towards you, it disrupts an even flow of air throughout the interior.
  • Do point the vents upwards for maximum effect and for the benefit of every occupant.
  • Don’t turn your air con up to the max when you get into the car -  it simply recirculates the hot air, while the air con tries to cool it.
  • Do lower your windows first and let some of the heat escape.
  • Don’t let the temperature climb in your car, it’s bad for your reaction times – use you air con, that’s what it’s designed for.
  • Do Keep the air recirculation on. Air con can cause the windows to fog up, but selecting the `Auto’ option lets it regulate itself, stopping this while keeping you cool.

Does air con use a lot of fuel?

Conventional wisdom has it that turning on your car’s air conditioning costs you up to 10% in extra fuel consumption, but like so many things in life, it’s rarely that simple.

Air conditioning is powered by the engine and anything which takes power from that increases fuel consumption. That much is perfectly true.

But, if you want to go into a little more detail you’ll find that how, where and when you use it are bigger factors and there’s another issue which needs looking at and it’s especially relevant this summer.


How should I use my car's air con?

First, let’s look at how you use your air con.

If you simply turn it up to the max as soon as you get into your car on a sweltering day and drive on a short, daily commute or shopping trip then you will see the mpg go down because the system will be working flat-out and will never really get the chance to run efficiently.

It’s better to open the window a little, let some heat out and then turn on the air con; it’ll have less work to do getting your car to the temperature you want and keeping it there and will be able to do that faster and more fuel efficiently.

Dog with head out of car window

Again, you may have heard people say that lowering the window as you drive causes air turbulence (true) which causes drag the car has to pull through the air which causes extra fuel consumption, again all true.

But, there’s ample evidence, from tests and data analysis, proving that if you have your window open at up to 40/50 mph, the fuel cost from that, is probably less than it would be with the air con at full blast; at motorway or dual carriageway speeds, it is better, and cheaper, to close your windows and let the ventilation do its job. It also saves your ear drums getting a bashing!

So, open the windows at first and get the temperature down a little, then press the A/C button.

And if you’re worried about a 10% rise in fuel consumption, there’s an easy solution - drive more economically. Most of us could easily make more than enough gains by driving smarter, to balance out the slight extra cost of the air conditioning.


Do I really need to use my air con at all?

Regardless of cost there’s another very good reason why you should use your air con, especially so this summer where we’re seeing record temperatures.

Earlier this year SEAT did some research into the effects of heat on drivers and the results are quite shocking.

They found that a difference of just 10°C, say 35°C inside the car compared to 25°C outside, can diminish reaction times by as much as 20%, that’s a fifth slower, or the equivalent to a blood alcohol reading of 0.05%, matching the Scottish limit and close to the maximum for the rest of the UK.

With outside temperatures recently soaring above 30°C in the UK cars can very quickly become ovens and drivers are at serious risk of dehydration. Cars parked in the sun can easily reach a startling 60°C, a whopping140 Fahrenheit!

Built up heat in a car reduces reaction times by 20%


Here’s some simple steps to get the most from your air conditioning:

  • Tempting though it is to turn the vents towards you, it disrupts an even flow throughout the interior. Point them upwards for maximum effect and for the benefit of every occupant.
  • Turning your air con up to the max as soon as you get into the car simply recirculates the hot air while the air con tries to cool it. Lower the windows first and let some of the heat escape.
  • Keep the air recirculation on. Air con can cause the windows to fog up, but selecting the `Auto’ option lets it regulate itself to stop this while keeping you cool.

Use the Auto control on your air conditiong for best efficiency