Re: air conditioning in cars - Is it the case that the colder the a/c, the more petrol you use?

Question

With air conditioning in houses, they say that you use less electricity when the a/c is on a warmer temperature, rather than freezing cold. Does this apply with car air conditioning as well? Does it use more petrol when colder and less when just cool, or the same amount of petrol either way?

Answer 1

Not really new A/C systems do not load the engine down enough to make much difference in fuel mileage.
Difference is in home units the compressor is run off electricity. The compressor is actually a combination electric motor and pump.
In a car the compressor runs off the engine Via a drive belt and power it draws from the engine is minimal.

Answer 2

I use to be in automotive engineer. I can tell you that running your A/C is virtually free. Here is what would make it cost more or less.
If you do a lot of city driving where you are constantly accelerating and decelerating. A/C will cost you more because during acceleration the A/C is using power that is needed for acceleration. Otherwise during crusing the engine has soo much built up momentum the load on the engine is minimal.
Most important How long do you drive. If you don't let your car cool down then drive you'll be less efficient. If you start it up and go then you get your car cool just in time to turn it off. Not only is this bad for the system you also have the compressor running almost the whole time your in the car.
Here is the facts.
The typical compressor is maybe 1/4 H.P. If you have a large luxury vehicle it may be 1/3 H.P. that is all the power you are robbing from the engine when you drive AND the compressor is running. once your car gets down to temp the compressor starts to cycle and you are using it even less.
Anyone who says they see mileage increases are because they are subconscienceously driving differently. That has much more of an effect on Fuel Economy then an Air conditioner. Don't accelerate as hard and try to coast to a stop. Don't drive over 60mph and you will save a bundle. Course people will be honking and flipping you off on the freeway.

Answer 3

When I disconnected the A/C in my car I got a good increase in mileage probably about fifteen percent better gas mileage. To run an A/C at a colder temperature it takes more energy to do this.

In most of the newer cars the A,C runs all the time at low power.When I disconnected mine I also removed the compressor belt. We had a few hot days last summer so we didn't drive unless we had to. When driving you can still keep cool with windows open.

Well I hope this helps and I believe A/C in the house will be much the same the harder it it run the more it costs

Answer 4

You don't get something for nothing so absolutely, yes it uses more petrol to have your ac colder. However there are a number of theory's on how much more petrol. If you were in the US, even paying nearly $3 a gallon, you probably wouldn't care. In the UK, it may be a different case.

Answer 5

you use less electricity in the house because it doesnt have to work as hard to keep it cold..
the same may be for a car.. im not positive.. I know my physics professor in high school said whether you use the a/c or leave ur windows open.. something about the pressure is making you use more gas per mile

Answer 6

It should be simple intuition here. The harder the AC is working to cool the air, the more energy it's using. In a car, the energy is created by burning fuel. In general, I believe running the AC at max would lower your fuel economy by about 10-15%.

Answer 7

It does put a load on the engine, but if you live in a climate where it is uncomfortably hot, your petrol bill every month is going to be about the same........

So use the AC

If you have it and it works, USE IT

Good luck

Answer 8

Actually Mythbusters showed virutally no difference between running an SUV with the A/C full-blast and one running with no A/C and the windows rolled down, so go for it