[Kirkwood]

Huh! You are just repeating what I said. You can't argue that it is an efficient or effective system though, because it simply is not. Do you always turn the faucet on full to fill a glass with water? Do you set your stove burner on full to warm up some soup. Do you accelerate your car to full speed and then slam on the brakes at the next stop light? Of course not, and yet this is how A/C works. How many times have you heard people complain that A/C leaves them either too hot or too cold? It is inefficient if you are using more energy than is actually needed at a given time. The solution has been to run the A/C and add warm air so you avoid the uncomfortable cycling and can zone different parts of living space to specific temperatures. You trade off energy efficiency for comfort.

[JAKraig]

Actually the solution for the last several years is to run the compressor and generate a pool of liquid refrigerant that continues to evaporate moving heat from inside the car to the refrigerant. Eventually all the pool is gas and the compressor comes on again. When the compressor comes on it compresses the low pressure gas into a high pressure gas and consequently high temperature gas where it is moved into the condenser. In the condenser the high temperature gas is cooled to a warm temperature high pressure liquid. Then we start all over again by allowing the warm liquid to move into the low pressure side where is evaporates and absorbes heat. The compressor does not stay on all the time but the cooling effect does.

[coloradan]

Do you always turn the faucet on full to fill a glass with water?

Thermodynamics doesn't come into play here, although a toilet tank does exactly that to fill.

Do you set your stove burner on full to warm up some soup.

No, because the soup would burn, something not at issue for the A/C.

Do you accelerate your car to full speed and then slam on the brakes at the next stop light?

No, because comfort is also a factor in the acceleration/deceleration profile of the ride, again, something not at issue with the A/C.

Of course not, and yet this is how A/C works.

None of your examples are good analogies. But, for example, a furnace is either on or it's off. So too with an electric blanket, or fishtank heater. In these systems, there's a lowpass filter that smooths the on-again, off-again input to an average value.

How many times have you heard people complain that A/C leaves them either too hot or too cold?

It's not my fault they can't adjust a knob - or aim the vents properly, or whatever. Neither does it disprove that the most efficient way to operate an air conditioner is by pulse-width-modulating the output, either at the most efficient place, or off entirely, and cycling fast enough so the net cooling is perceived as average, as opposed to on-again, off-again.

It is inefficient if you are using more energy than is actually needed at a given time.

Instantaneously, yes, on average, no. It's more inefficient to run it all the time, at an operating point with lower efficiency.

The solution has been to run the A/C and add warm air so you avoid the uncomfortable cycling and can zone different parts of living space to specific temperatures. You trade off energy efficiency for comfort.

You made my point for me ... you are now admitting that you are trading away energy efficiency.