Air Conditioning Vs. Windows Down: Which Is Best?


Is the cost of using your car AC worth it when you could simply roll down your windows for free?

Read in this article:

The Fuel-Use Debate - Car AC or Windows Down?

There is a school of thought that claims your car AC is a huge drain on your car engine and that it has a noticeable effect on your fuel usage. Another group claims that car air-conditioning is actually very efficient and that the drag caused by open windows is a larger detriment, especially on the highway. So, how much does the AC affect gas mileage as opposed to open windows, and what factors do you actually have to consider when making the calculations?

Using Air-Conditioning

As is to be expected, there are documented advantages and drawbacks to either choice. To be able to weigh the two properly, you need to know the pros and cons of using air-conditioning or climate control.

Pros and Cons

  • Convenience: A simple press of a button is all it takes to cool down the interior, even on a sweltering day when you can feel the burn of the sun.
  • Cleaner air: Almost all modern cars sold in the US have cabin filters that remove dust and pollen from the incoming air. You're breathing cleaner air with the AC on and the windows closed.
  • Faster demisting: Blending in air-conditioned air when your car's demisting function is used speeds up the process because the AC dries out the air and removes moisture from the glass faster.
  • Increased fuel consumption: The air-conditioner compressor runs off the engine with a belt and steals horsepower, which, in turn, uses extra fuel. In an SUV with a powerful AC, such as a Land Rover Defender, the fuel drain is significant.
  • Drains engine power: The air-conditioner can drain a noticeable amount of engine power, depending on the type of car. Small hatchback cars with weak engines suffer most. Sports cars with powerful engines simply shrug off the load.
  • Engine temperature: The AC places extra demands on an engine, so make sure your car's cooling system is in good condition.
  • Can cause irritation: Because of its drying effect, an air-conditioner can irritate some people and dry out their eyes.
Air Conditioning
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Rolling Your Car Windows Down

Then there's the alternative. Sometimes, you don't need a high-tech solution to a problem, when a more analog one can do the same job. Still, there are reasons we create technology to perform seemingly mundane tasks, so what's actually good and bad about driving with the windows down?

Pros and Cons

  • Fresh air: Driving by the ocean or in nature, nothing compares to the fresh air and fragrances of the outside world that come from driving with your car windows down.
  • Awareness: You can hear what's going on around you clearly, whether it's an ambulance to yield for or the call of an elusive bird you are trying to find.
  • Initial cooling down: Nothing gets rid of hot air trapped in a vehicle that was parked in the sun faster than rolling the windows down and letting the wind blow through the car.
  • Increased fuel consumption: Having the windows down causes significantly more drag, especially at highway speeds, as the air no longer flows over the car's smooth skin, but is interrupted by the window openings. This increased drag impacts MPG.
  • Dust and pollution: Dust, pollen, smoke, and strong smells can enter the cabin without wastehindrance through the open windows.
  • Noise: The rush of buffeting wind, especially at high speed, creates a lot of cabin noise.
  • Still ineffective: On a hot day in traffic with no wind - as is typical summer weather in many cities in the USA's Midwest - open windows will not do much to cool you down.
Car Window Open

Tips on How to Cool Down Your Car’s Interior Quickly

If your car has been standing in the sun for hours and feels like a sauna when you get in, try the following:

  • Open all the windows immediately
  • Start driving to let the car air out
  • Set the air-conditioning to cold
  • As soon as air-conditioned air arrives, close the windows
  • Don't waste fuel by driving with both an open car window and the air conditioner operating

How Much Does the AC Affect Gas Mileage?

Luckily, there have been multiple studies on this particular subject, so there is a fair amount of data corroborating the findings. Using your air-conditioning uses more gas than opening your windows, especially in city traffic or when driving slowly. At speed, open windows' added drag plays an increasingly important role, but it still wastes less fuel than using the air con. So, how much gas does the AC use? Up to 25% more, especially on short trips. So in the battle of air-conditioning up vs windows down, open windows are better for fuel economy.


What is the moral of the story? Open your windows whenever you can and only use your air-conditioning when you have no other choice, such as on the open road, when nothing else cools you down, or in dusty conditions. This is the best way to save fuel while still enjoying the benefits of air-conditioning when you need it, as permanently leaving the air-conditioning on wastes gas.

Fresh Air in Car


When should I use my air-conditioner?

Use it mainly on the highway, where it is inconvenient and noisy to drive with open windows. To save fuel, drive with open windows whenever possible. However, it is still necessary to turn it on every week or two, even if just for a few moments. This helps keep the seals lubricated and prevents the system from developing premature leaks.

Why does my air-conditioner not blow a lot of air anymore?

Chances are good that your cabin filter is blocked and should be replaced. Other possible causes for low flow include frozen evaporator coils or leaky/blocked air ducts.

How do I know whether the air-conditioner is on?

There should be a light glow from the AC button. Climate-control systems should show a snowflake icon or something similar to indicate when the air-conditioner is running. It should have an override, too, to switch it off. You will obviously also feel cool air from the vents.

Does an AC use gas?

ACs use refrigerant gas, yes, and over time pressurized systems like this can begin to leak. Symptoms of a potential refrigerant leak include warm air blowing from the vents or a thin, greasy substance leaking around the compressor. First check for leaks before simply refilling with gas.

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