How much gas does the AC eat up?

with many cars the compressor will engage with the heat switched on as well as the air so the extra effort the engine uses to turn it will use more gas. Sitting in 1 place for an hour means the car is getting zero miles per gallon.

Id say your honda’s heater is just picking up wast heat from the engine with a fan.
So your just wasting fuel mostly. AC is different, compressor etc.

Both correct; you are getting zero MPG and that the heat is effectively free as it is waste heat from the engine that would be there anyways, and the compressor causes the engine to use more gas.

As for how much more, that depends a bit on the car. My old Corolla barely noticed the compressor and it didn’t have any noticeable effect on fuel consumption whereas my old Saturn would see the MPG drop by 10–15% and had a hard time making hills with the A/C on.

Running the AC will use slightly more gas however its probably no more than that used by the increased drag of having a couple of windows open.

@Lightlyseared Not an issue when you’re parked :D
FYI, once you get over about 60 MPH, the A/C uses less gas than an open window.

Yes, your AC is using a little more gasoline to keep you cool. and no, using just the heater does not take the fuel useage, compared to the AC.

But, i say this….....for ones sanity(and i understand your comment), i will spend a little more for air or heat, just to be alone sometimes. its worth it.

yes the heat is already there from the hot coolant circulating but without the fan switch on it won’t feel like much just ebbing out of the ducts. Usually once the fan is switched on even if it is on low, the compressor will kick on. You really get the full benefit from the heat with no fan when the car is moving. It just seems to force it out better. Of course different vehicles are designed differently. During the summer months when we never use the heat, it was common for the compressor to seize up from lack of use causing a very expensive repair bill come summer. With the compressor in use even in the winter keeps it working so it isn’t getting stuck. The extra money we spend in fuel doing this in the winter doesn’t even come close to the cost of replacing that compressor later.

wow great answers! this makes me so happy lol

2 to 10% depending on how big the engine is. I have a Nissan that uses an extra 3mpg when the A/C is on. The heater may suck .1% note: POINT ONE PERCENT since you’re not engaging the A/C compressor, only using a little more electrical power from the alternator..

This question cannot be accurately answered as there are too many variables.

AC compressors are increasingly more efficient as technology improves.

V6 equipped Accord coupe. Congrats!