Is It More Efficient to Drive With Your Windows Down or Up With AC On

Driving in a hot car on a very humid day is no doubt uncomfortable. And, as summer hits its peak time and the temperatures increase, chances are you're going to turn to cranking up the air conditioner in your car. However, if you're looking to save money and fuel, is turning the AC on a good idea or would rolling down the windows be a better choice?

Windows Down or AC On?
Rolling your car windows down decreases gas mileage since it increases drag and wind resistance. The drag of your car is how much resistance it has to the moving air across your car as you're driving. Low to the ground and sleek cars (i.e. electric vehicles or sports cars) have comparatively less drag, contributing to better gas mileage. Trucks with boxy shapes and large, tall cars have a lot more drag which contributes to fairly low gas mileage.

When you drive with your car windows down, it will increase your car's drag, but this is:

  • Impacted by the speed your car is going
  • Relative to the design of your car

To put it simply, a tall, large SUV does push a great deal of air while it's moving. Open windows on a SUV might add fairly little to the substantial overall drag. On the other hand, a sleek, low roadster is made for a lot less drag and when you open the windows, it could raise the overall drag in greater proportion.

Another factor is speed, as the open windows' drag raises with higher speed. And, this is true no matter what type of car you have. Opening up your windows will use more gas when you're driving at highway speed than it will when you're driving around town.

But, There have been various debates on which vehicle cooling method is more fuel efficient:

  • Driving with the windows down
  • Cranking the air conditioner

Both lead to burning more fuel, but which burns more?

As mentioned, you increase drag while you drive with open windows. However, when you run the air conditioner, it burns fuel to run. So, to find the answer to the above question, there was a test conducted.

For the test, cars were compared driving 31 mph, 50 mph and 68 mph. It was 86 degrees Fareneheit. Results of the test showed it was more fuel efficient to drive with the windows down than it was to run the AC.

What About Your Home?
When it comes to your home, running a whole house fan is more efficient than running an air conditioner. You can cool your home faster with a whole house fan than you can with an AC unit. And, you don't need to leave the whole house fan on all day, like you do with your air conditioner.

 As you see, whether you're home or driving your car, it's more efficient to rely on the natural flow of the air than it is to crank up your air conditioner.