The short answer is yes, they can…sort of. The long answer is, it depends on where you draw the line between efficient and inefficient.
The answer also depends on the type of vehicle, temperature, and condition of your AC system.
Fuel consumption does not dramatically increase the moment you switch on the AC. However, because automotive AC units rely on the engine for power, the engine does have to ask a little more of the gas tank to maintain its speed.
But, let’s start by putting fuel economy in perspective. Yes, air conditioning diminishes your overall MPG. There’s no way around it.
What are the alternatives on a hot day? Walk? Bus? Windows down? Air vent? Hitchhike? All but one of these options are great ways to avoid unnecessary spending at the pump.
Far too many drivers believe that rolling the windows down is both earth-friendly and economical. The sad truth is that it’s neither.
Driving at highway speeds with the windows down, neglecting a perfectly healthy AC system actually creates drag as air forcefully hits the back windows.
A study was done by the Society of Automotive Engineers (SAE) in 2004, finding that fuel consumption increased 20 percent while driving an SUV at 50mph with the windows down. Consumption increased only 10 percent while driving the same car at the same mph with the windows up and the AC on its coolest setting at medium speed.
For the best of both worlds – fuel economy and a comfortable ride, be tactful about when and how you use your air conditioning.
Here’s a quick guide to maximizing fuel efficiency and staying comfortable in the car when it’s warm outside: