Car care · Elgin Auto Sales & Service Center · Elgin, IL
Does Car AC Use Gas?
Does running the air conditioner burn more gas, and is it better to roll the windows down? Here is what fueleconomy.gov, the U.S. Department of Energy and EPA fuel economy site, says.
Over 25%possible mpg loss from AC in very hot weather
Highwayuse the AC
Lower speedsroll the windows down
Main factorin hot-weather mpg
The short answer
Yes. Fueleconomy.gov says running the air conditioning is the main contributor to reduced fuel economy in hot weather. Under very hot conditions, AC use can reduce a conventional vehicle's fuel economy by more than 25%, particularly on short trips, and the effect on hybrids, plug-in hybrids and electric vehicles can be even larger on a percentage basis. Open windows cost fuel too, mostly at highway speeds, so the advice is to roll the windows down at lower speeds and use the AC at highway speeds.
How much gas does the AC use?
Running your car's air conditioning is the main contributor to reduced fuel economy in hot weather. How much it costs you depends on several factors, including the outside temperature, humidity and the intensity of the sun.
Under very hot conditions, fueleconomy.gov says AC use can reduce a conventional vehicle's fuel economy by more than 25%, particularly on short trips. The AC's effect on hybrids, plug-in hybrids and electric vehicles can be even larger on a percentage basis.
Hot weather by itself can actually help fuel economy: the engine warms up to an efficient temperature faster, summer grades of gasoline can have slightly more energy, and warm air causes less aerodynamic drag than cold air. It is keeping the cabin comfortable, with the AC or open windows, that costs fuel.
From Fuel Economy in Hot Weather (fueleconomy.gov), read November 9, 2026.
AC or windows down: which uses less gas?
Open windows increase aerodynamic drag, so the car uses more energy to push through the air. Fueleconomy.gov says that effect is quite small at low speeds but increases at highway speeds:
| Driving | Better choice for fuel economy |
|---|---|
| Lower speeds, around town | Roll the windows down. Drag from open windows is quite small at low speeds. |
| Highway speeds | Use the AC. Drag from open windows increases at highway speeds. |
From Fuel Economy in Hot Weather (fueleconomy.gov), read November 9, 2026.
Tips to use less fuel with the AC
Fueleconomy.gov recommends these steps in hot weather:
- Roll the windows down at lower speeds and use the AC at highway speeds.
- Do not use the AC more than needed or set the temperature lower than needed.
- Park in the shade or use a sunshade so the cabin does not get as hot.
- Drive with the windows open for a short time before using the AC. Letting hot air out first puts less demand on the AC and helps the car cool faster.
- Do not idle with the AC running before you drive. Turn the AC on after you start driving or after airing out the cabin briefly; most AC systems cool the car faster while driving.
- Read your owner's manual. Most manuals explain how the AC controls work and how to best use and maintain the system.
- In a plug-in hybrid or electric vehicle, pre-cool the cabin while plugged into the charger to extend range, and use a warmer AC setting to use less battery power.
From Fuel Economy in Hot Weather (fueleconomy.gov), read November 9, 2026.
Service at Elgin Auto Sales & Service Center
Need maintenance or a check of your car's systems? Schedule service or see our service specials.
Our service department at 1200 E. Chicago St. in Elgin is open Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m., and is closed Sunday. Get directions.
Car AC and gas mileage FAQ
Does using the AC in a car use more gas?
Yes. Fueleconomy.gov says AC use is the main contributor to reduced fuel economy in hot weather, and under very hot conditions it can cut a conventional vehicle's fuel economy by more than 25%, particularly on short trips.
Is it better to use AC or roll the windows down?
Roll the windows down at lower speeds and use the AC at highway speeds, where open windows add more aerodynamic drag.
Should I idle with the AC on before driving?
No. Fueleconomy.gov advises against idling with the AC running before you drive; most AC systems cool the vehicle faster while driving.
Does AC affect hybrids and electric cars more?
On a percentage basis, the AC's effect on hybrids, plug-in hybrids and electric vehicles can be even larger than on conventional cars.
How can I cool my car faster and use less fuel?
Park in the shade or use a sunshade, drive with the windows open briefly to let hot air out, then switch to the AC once you are moving.
What are your service hours?
Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m. We are closed Sunday.
AC not keeping you cool?
Visit us at 1200 E. Chicago St. in Elgin.
Sources
Air conditioning and fuel economy guidance is from fueleconomy.gov, administered for the U.S. Department of Energy and the EPA, read November 9, 2026. This is general information; your owner's manual is the authority for your vehicle. Our address and service hours are from our own website, checked the same day. Photo is of our dealership.
- Fuel Economy in Hot Weather (fueleconomy.gov), U.S. Department of Energy and U.S. EPA, read November 9, 2026
- Home page: address, Elgin Auto Sales & Service Center, read November 9, 2026
- Service page: service hours, Elgin Auto Sales & Service Center, read November 9, 2026