Gas Mileage Using the AC or Heater
Does Running the Heat or AC Use Gas?
We all have that one friend. It’s 102 degrees out, and they insist that it’s more economical to keep the windows down and not run the air conditioning as they don’t want their gas mileage to plummet. The bad part is, no matter what facts or figures you throw at them, they’re always going to believe that windows down is more efficient.
So who is right? Is it better to let the breeze in, or kick on the air conditioning? And since we are into heating season now, is it better to suffer in the cold, or open those vents up and let the sweet warmth wash over you? As the premier collision repair shop in the area, we went ahead and researched it for you.
Windows Down vs. Running the Air
Kicking on the air conditioner means you’re running the condenser. That little device sucks up a lot of power, and generally uses about 10% of the horse power that your engine is putting out. Here’s how that breaks down to your fuel economy.
Suppose you are driving a Honda, and that vehicle is getting around 30 miles per gallon. You turn on the AC, and your horse power drops from about 180 to 162. If you have ever turned the AC on while cruising down the highway, you probably know the feeling; that sudden lag in the engine.
Diverting those 18ish horsies to the air conditioner means that your 30 miles per gallon drops to around 28 or 28.5. Over the course of 550 miles, you burn through around 1 extra gallon of gas.
So letting the breeze in is better… right? Not exactly. At higher speeds, the added drag means the engine has to work harder. The result is that your fuel efficiency can drop by as much as 10%-20%. Your 30mpg goes down to between 24 and 27mpg. That same 550 miles would burn 2 to 4 more gallons than driving windows up and AC off.
Of course, that’s on the highway. Go into town, and it’s a different story with stop and go traffic, lower speeds, and less drag. Your best bet, however, is still to crank the AC.
Turning on the Heater vs. Braving the Cold
Since we run our heat more often than our air conditioners here in Billings, let’s look at the more common question. Does it burn more fuel to run the heater, than to try to bundle up and brave the cold?
Assuming that you’re not out there letting the car warm up for half an hour before you hop in, the answer is: sort of.
Because your vehicle runs on an internal combustion engine (electric cars are a different story), the vehicle is already producing heat. And it’s producing much more heat than you would need inside the cab. Kicking on the heater just diverts the heat into where you are instead of dissipating into the air around you. The extra energy to run the fan is all the power that is diverted from moving the wheels.
The bottom line is that running the heater uses so little extra gas that you could drive for many thousands of miles blowing the heat full force without noticing a difference in fuel economy.
Auto Body Repairs in Billings, Montana by Big Sky Collision Center
Here at Big Sky Collision Center, we are always working toward being the best auto body repair shop in Billings. If you have hail damage, collision damage, or otherwise need your vehicle fixed back to full factory safety standards, then just give us a call at 406-259-6328 and we will get you on the schedule.