A/C in a Car: Does Cranking It Really Use More Gas?

A/C systems in a car may place a strain on your engine, which can reduce fuel efficiency. But is your car’s A/C draining your wallet?

Elliot Rieth | 

Jun 3, 2026 | 5 min read

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The New York Department of Transportation says that if you're trying to save on gas and looking for an easy rule of thumb, consider using the A/C when driving on the highway at speeds above 40 or 50 miles per hour, and when you're driving through a city at a slower speed, roll the windows down.

So how do you stay cool without paying extra at the pump? Learn what you can do to avoid the costly consequences of overusing your car’s A/C.

• How the A/C impacts fuel consumption
  
• A/C vs. windows down: The Great Debate
  
• Factors that can influence A/C fuel drain
  
• 5 practical tips to save fuel while staying cool

How the A/C Impacts Fuel Consumption

Your car's A/C runs thanks to a compressor connected to your engine, which requires your engine to use more energy to circulate refrigerant through your A/C system. The compressor doesn't consume fuel on its own. However, according to the Universal Technical Institute trade school, the additional strain running the A/C places on your engine reduces your overall fuel economy.

Using the DOE’s 25% cut on fuel consumption on a hot day, that could mean up to a 7.5 mpg loss on a car that gets 30 mpg in the city.

Automotive expert and journalist Brian Moody says gas prices can vary depending on the time of year, demand, and global circumstances.

“With a very thirsty vehicle, the impact to your finances can be significant,” Moody says. “With a large truck or truck-based SUV, the costs can rapidly go up. However, a hybrid or modern sedan will minimize the impact. Because fuel prices fluctuate frequently, it’s important to consider fuel economy and future gas prices when selecting a new or used car.”

The DOE said an EV’s battery drain can be even higher since the A/C system is powered by an electric motor instead of an engine. This motor will draw off your EV's overall power supply.

“Blasting the air conditioner when it’s hot outside cuts the battery range,” the DOE reports.

Still, automakers like Kia and Hyundai come equipped with a “Driver Only” A/C mode or similar button that directs cool air on the driver so you’re not cooling down the whole car when there’s a single occupant.

Moody says using the button can cut down on batter usage.

A/C vs. Windows Down: The Great Debate

Whether you should rely on A/C or the car windows down may depend on how fast you're driving. According to the NYDOT report, using the A/C and rolling down windows can negatively affect your overall fuel economy by as much as 20%. However, when it’s scorching hot, driving with the A/C on impacts your fuel economy more at low speeds, and windows down have more impact at high speeds, according to the NYDOT findings.

The key difference is the drag factor. If you're driving faster than 40 or 50 miles per hour (such as on the highway), the aerodynamic drag and wind resistance associated with rolled-down windows can have a greater negative impact on fuel economy than A/C use, according to the NYDOT report. And if you're driving slower (like in the city), drag is a less significant factor and won't compare to the strain that A/C puts on your engine.

Factors That Can Influence A/C Fuel Drain

Your A/C fuel drain can also be impacted by temperature, humidity, and maintenance. Higher temperatures and humidity force your A/C to work harder to cool the inside of your vehicle, placing greater strain on your engine and reducing fuel efficiency. 

Meanwhile, how well your A/C system is maintained will determine its overall efficiency and the strain your compressor endures while operating. Regular maintenance can reduce A/C problems that may negatively affect your fuel economy. But even the best-kept A/C systems will still impact gas usage.

5 Practical Tips to Save Fuel While Staying Cool

Although running your A/C will almost always affect fuel economy, there are ways to reduce fuel consumption. Try these practical tips to increase fuel efficiency in the name of keeping cool:

• Vent Out Hot Air: Rather than cranking your A/C the moment you get into a hot car, drive with the windows down for a short while to clear out any stagnant hot air. This makes it easier for your A/C to cool your car down when you turn it on. If you drive a plug-in hybrid or EV, you could also consider cooling your cabin down while plugged in to preserve your driving range.
• Try Recirculation Mode: This setting offers a more gas-friendly alternative to normal A/C use by reducing strain on the compressor.
• Park in the Shade: Parking your car in a covered spot can reduce heat buildup inside and resulting A/C use. You can also try using a sunshade to keep the interior temperature lower.
• Don't Run the A/C While Idling: Most modern A/C systems cool more efficiently when your car is moving, and idling already negatively impacts fuel economy. For stop-start cars, you may consider turning this function off, as turning your A/C on and off at every stop will require it to compensate for a higher overall cabin temperature.
• Use Eco-mode: If your car has an eco-mode option, it could place less strain on your engine by reducing functions like A/C output. This results in a better overall fuel economy when combined with conservative driving habits.

As you use these tips, keep a close eye on your fuel consumption to see which options make the biggest difference for your gas tank. Of course, use the strategies that make you or your passengers comfortable.

Elliot Rieth

Born and raised in Michigan — the center of the American automotive industry — Elliot's fate of becoming a writer in the automotive space was seemingly predetermined. In addition to covering cars and personal finance for Capital One, he's worked directly with dealers and OEMs to create digital content meant to educate consumers. He's also passionate about music and has written for outlets like In Review Online. When he isn't writing about the latest financial, automotive, and insurance trends, he can be found enjoying a new book or record alongside his two greyhounds.