What exactly does driving with the A/C on and the windows open do to a car?

Question

Or home?

Answer 1

Burns extra fuel and makes it not AC'ed in the car.

Answer 2

In both cases you will have a greater consumption (of fuel or electricity) and possibly higher temperatures (if the exterior temperature is very low, that obviously won't be the case).

But that is only the theory, in practice, many factors affect the "how much" and make the difference negligible. For example, if you home AC is set at 75F and the exterior temperature is 110F, leaving the windows open will have a greater effect on consumption and temperature than if the outside temperature is, say, 80F. And if the outside temperature is bellow 75F but the sun in shinning bright, leaving windows open will actually be cheaper (zero) than shutting them.

Still on the house example (much easier to analyze), other things that will affect the scale of the impact are: wind speeds and direction in relation to window(s), total window area in relation to house volume and AC capacity and position of the thermostat in relation to AC outlets and window. Although there will always be more consumption and higher inside temperature (unless the outside temperature is lower), the actual effect may not be perceptible in some cases. As a rule though, you will start paying extra before you start feeling hotter.

Many of these considerations also apply with a car, but also several others. For example, the wind speed becomes the car speed, but the effect of opening windows on a moving car is ALWAYS more fuel consumption, regarless of AC being on or not. However, the percentage of this increase will depend on the speed and on the car's aerodynamics. For large and boxy SUVs and trucks, the difference may be too small to count. The same may apply for any car moving at low speeds.

The consumption effect of turning on the AC on a car will also depend a lot on the engine's power/tork. For larger engines, the extra load may be negligible. For small fuel efficient ones, it won't.

Another factor to be considered is if the car's AC has a thermostat, not all do.

Answer 3

well with just the ac on you use a small fraction more gas, and you don't die from heat exhaustion.

with the windows open you use a fraction more gas from the added drag the open windows cause, but if you don't have ac, it helps you not die from this hot weather.

now as for doing both at the same time, doesn't really make any sense unless you just got in a car that was siting outside and is a billion degrees inside. have the windows open as the ac starts to kick in, then once it is goin shut them for the best results.

Answer 4

Well, in your home it causes the AC to run more...you have a thermostat that's trying to get the temperature down to what you set it for. Of course, the more the AC runs, the more electricity you consume and the higher your utility bill.

In your car..unless you have one of the cars with an AC thermostat inside that turns the AC on and off...you're doing two things...with the AC on you put more wear on your car engine. AC "draws" off the engine's power, so more draw...more wear..engine has problems sooner. If you're running with the windows down, if you're on the interstate, you're making your car less aerodynamic, which causes the engine to work harder. One or the other....not both. Non-interstate - windows down is best. Interstate - AC.

If you have a thermostat in your car, you're running the AC trying to cool the car interior to a specific temp....probably not a good thing.

Answer 5

A/C has a cut off mechanism called Thermostat . its feature is is to cut off cooling when the required temperature is reached., That will happen only if it is and enclosed space that is the windows have to be closed.
If you open the windows its no longer and enclosed space . So the thermostat will never be off. so it will over load the compressor long enuff that long term use of A/C with windows open can damage the compressor as it is against is principle.

Also you waste energy and gas as well .

Answer 6

nothing except use more gas. if you want windows down, turn the a/c off. if its hot and you want the best comfort with the best fuel milage, use the the a/c. a car will get better fuel milage with the a/c on windows up versus running with the windows down due to the extra drag it causes.

in the house, just runs up your electric bill if you run the a/c with the windows open and extra wear on the unit and makes you have to change the air filter more often.

Answer 7

The Myth Busters did a study about it. It was determined that an SUV got more miles to the gallon with the A/C on and the windows up. With windows down, aerodynamics is significantly reduced causing drag, thereby decreasing fuel economy....

Answer 8

The interior temperature would never reach what the thermostat is set for, making the engine work harder to keep the cooler going. Inside the house, it just would keep the AC running all the time and your bill would be sky high--probably wear out the AC unit that much faster as it is running constantly instead of intermittently.

Answer 9

windows down increaces drag. Running the system creates drag on the engine. another words save yourself some money roll the windows up.

Answer 10

Ive never driven my home with the windows open or the air , come to think of it ive never driven my home at all.

Answer 11

in the car? nothing
At home - makes you spend more money as your A/C unit runs constantly. This occurs because the A/C unit(central air) works to statisfy the thermostat.