To save money at the pump, many drivers look for ways to improve their vehicle's fuel efficiency. Maintaining proper tire pressure, for example, is a well-known way to improve fuel efficiency. When your vehicle's tires are properly inflated to the pounds per square inch (PSI) as specified by the manufacturer, your vehicle will consume less gas. Another common practice drivers use to improve fuel efficiency is not running their air conditioner (AC). Being that automotive AC systems use electricity and not gas, though, you might be wondering if there's any merit to this practice.
Yes, the AC Consumes Gas
The short answer is yes -- running your vehicle's AC will consume gas. Some vehicles burn more gas when the AC is running than others. Nonetheless, research shows that running the AC will reduce a vehicle's fuel efficiency by roughly two or three miles per gallon (MPG). The longer you run the AC, the more gas your vehicle will consume.
Why the AC Consumes Gas
Running the AC will make your vehicle less fuel efficient because it draws power from the engine. As you may know, the AC uses electricity, which is generated by the alternator. Alternators, of course, require their own power, which usually comes from the engine. As the engine burns gas and air, it generates power that turns the alternator's serpentine belt. Therefore, your vehicle's engine will burn more gas when the AC is running.
Don't Roll Down Your Windows as an Alternative
While running the AC will make your vehicle less fuel efficient, that doesn't necessarily mean you should roll down the windows as an alternative to stay cool during the summer months. With the AC turned off, your vehicle's engine won't need to burn as much gas. If you open the windows, though, it will make your vehicle even less fuel efficient.
According to the U.S. Environmental Protection Agency (EPA), vehicles burn more gas with the windows down and the AC off than they do with the windows up and the AC on. This is because rolling down the windows will make your vehicle less aerodynamic. Air won't be able to glide smoothly over your vehicle's body if you roll down the windows. In response, your vehicle's engine will have to burn more gas to compensate for this loss of aerodynamics.
It's true that running the AC will make your vehicle consume more gas. With that said, you shouldn't roll down your windows as an alternative. Rolling down the windows is actually worse than not running the AC because it makes your vehicle less aerodynamic.