Yes, using air conditioning increases fuel consumption, but the amount depends on your car, the outside temperature, and how you drive
When you run your air conditioner, your engine works harder to power the compressor that cools the air. That extra work burns more fuel. On average, air conditioning use can increase fuel consumption by 5 to 25 percent, though the real number for your car falls somewhere in that range depending on several factors. The hotter it is outside and the colder you set the temperature inside, the harder your air conditioner has to work — and the more gas you burn.
The effect is most noticeable in city driving, where your engine is already working at lower efficiency. On the highway, the difference is smaller because your engine runs more efficiently at steady speeds. If you drive a smaller, lighter car, the impact of air conditioning is more visible on your fuel economy. If you drive a larger vehicle, the air conditioner's demand is a smaller percentage of the total fuel your engine uses.
Key Takeaways
- Air conditioning increases fuel use because it forces your engine to power the compressor, with the effect ranging from 5 to 25 percent depending on your vehicle and driving conditions.
- City driving shows a bigger fuel economy drop from air conditioning than highway driving, because stop-and-go traffic already stresses fuel efficiency.
- The hotter the outside temperature and the lower you set your interior temperature, the harder your air conditioner works and the more fuel it burns.
- Opening windows at highway speeds uses more fuel than running air conditioning, because wind resistance creates drag that forces your engine to work harder.
- Maintaining your air conditioning system — keeping the refrigerant charged and the compressor functioning properly — prevents it from working overtime and wasting extra fuel.
Why air conditioning makes your engine burn more fuel
Your car's air conditioning system is powered by a belt connected to your engine. When you turn on the air conditioner, the compressor — the part that pressurizes refrigerant to create cold air — engages and draws power directly from the engine. That power has to come from somewhere, and that somewhere is the fuel you are burning.
The harder the compressor works, the more fuel your engine consumes. On a 95-degree day with your air conditioner set to 60 degrees, the compressor runs continuously and works at maximum capacity. On a 75-degree day with the air conditioner set to 72 degrees, the compressor cycles on and off and uses less fuel. The difference between these two scenarios can be substantial over a long drive.
How temperature and driving conditions affect fuel use
City driving amplifies the fuel penalty of air conditioning. When you are accelerating, braking, and idling in traffic, your engine is already less efficient than it is on the highway. Adding air conditioning demand on top of that inefficiency creates a noticeable drop in miles per gallon. Some drivers report losing 10 to 15 percent of their fuel economy in summer city driving when the air conditioner is on.
Highway driving shows a smaller effect. At a steady 60 or 70 miles per hour, your engine operates in its most efficient range. The air conditioner's demand is real, but it is a smaller percentage of the total fuel your engine is already burning. You might lose 5 to 10 percent of highway fuel economy with air conditioning on, depending on how hot it is outside.
The outside temperature matters more than you might think. On a mild 70-degree day, your air conditioner does not have to work hard to maintain a comfortable interior temperature. On a 100-degree day, the compressor runs harder and longer. The difference in fuel consumption between these two scenarios can be 10 percent or more.
Air conditioning versus open windows at highway speeds
Many people assume that rolling down the windows and turning off the air conditioner saves fuel. At low speeds, this is true — opening windows creates minimal wind resistance. At highway speeds, the opposite happens. When you drive 55 miles per hour or faster with the windows down, wind resistance increases dramatically, and your engine has to work harder to push through that resistance. This drag effect actually burns more fuel than running the air conditioner.
The crossover point — where air conditioning becomes more efficient than open windows — happens around 45 to 55 miles per hour, depending on your car's shape and size. For city driving and slower speeds, open windows are the more fuel-efficient choice. For highway driving, air conditioning is more efficient. On a long highway trip, running the air conditioner and keeping the windows closed will use less fuel than opening the windows.
How to reduce fuel consumption when using air conditioning
Set your air conditioner to a reasonable temperature rather than the coldest setting. Every degree lower increases the compressor's workload. Setting the temperature to 72 or 73 degrees instead of 60 degrees can noticeably reduce fuel consumption, especially on long drives. You will still be comfortable, and you will burn less gas.
Use the recirculation mode when your air conditioner is on. This mode recycles the cold air already inside your car instead of pulling in hot outside air and cooling it. Recirculation reduces the compressor's workload and saves fuel. Many cars have a button labeled with a curved arrow or the word "recirculate" on the air conditioning control panel.
Keep your air conditioning system maintained. A refrigerant leak or a compressor that is not functioning properly forces the system to work harder and burn more fuel. Have your air conditioning serviced if it is not cooling as well as it used to, or if you notice a drop in fuel economy that coincides with warm weather.
Park in the shade when possible. A car that is already hot when you start it forces the air conditioner to work harder for the first several minutes of driving. Parking in the shade or using a sunshade reduces the interior temperature and means your air conditioner does not have to work as hard initially.
The real-world difference in your fuel costs
The actual fuel cost of running your air conditioner depends on how much you drive, how often you use it, and current gas prices. If you drive 12,000 miles per year and use your air conditioner for half of those miles, and air conditioning increases your fuel consumption by 15 percent, you are burning roughly 900 extra gallons per year because of the air conditioner. At current gas prices, that could add $1,200 to $1,500 to your annual fuel costs, though this varies by region and season.
For most people, the fuel cost of air conditioning is worth paying to stay comfortable and safe while driving. Overheating can impair your judgment and reaction time, and driving with the windows down at highway speeds is less safe than driving with the windows closed. The fuel penalty of air conditioning is real, but it is usually smaller than the benefit of staying alert and comfortable behind the wheel.
Frequently Asked Questions
Does air conditioning use more gas than heat?
Air conditioning uses more fuel than heat. Heating uses waste heat from your engine, which is already being produced. Air conditioning requires the compressor to actively work, drawing power from the engine. Heat is essentially free; air conditioning costs fuel.
Will turning off air conditioning on a hot day save a lot of gas?
It will save some gas, but probably not as much as you think. On a 90-degree day in city traffic, you might save 10 to 15 percent of fuel consumption by turning off the air conditioner. On the highway, the savings are smaller — closer to 5 to 10 percent. Whether it is worth the discomfort depends on your priorities.
Does air conditioning affect fuel economy more in newer cars or older cars?
Newer cars have more efficient air conditioning systems and engines that are better at handling the extra load. Older cars often show a larger fuel economy drop when air conditioning is on. The difference can be 5 to 10 percentage points between a 2005 model and a 2020 model.
What is the best temperature to set my air conditioner to save fuel?
Set it to the highest temperature at which you are comfortable — usually 72 to 75 degrees. Every degree lower increases fuel consumption. On a long drive, raising the temperature by just 3 degrees can save 5 to 10 percent of the fuel your air conditioner uses.
Does idling with air conditioning on burn a lot of gas?
Yes. When you are idling, your engine is not moving the car forward, so all the fuel it burns is going to power the air conditioner and other systems. If you are stopped for more than 10 seconds, turning off the engine and restarting it when you are ready to move uses less fuel than idling with the air conditioner on.