Turning the AC completely off when you leave the house is not the right thing to do, and neither is turning it on at full blast when you return home. The optimum thing to do is to set it at a "tolerable" temperature--about 80-82 degrees when you leave. It might get a little warm in the middle of the day, but the air will keep circulating and it won't be stifling when you get home. You can then turn it down to 78-79 degrees, That's not too cold, and it won't put a strain on the compressor. An additional thing you can do is to run your ceiling fans while you're gone. We live in Dallas, and it gets over 100 degrees many days during the summer. This is how we handle our air conditioning. Same thing in the winter, only in reverse. Our "away" temperature is 65-68, and when we get home, we bump it up to 74-76, depending on how cold it is outside. (We don't have winter "extremes" here). This will save on your electric bill if you will be consistent with the temperatures.