The first thing to know about central air conditioning is that turning the thermostat way down doesn't make the house cool down faster. The thermostat is not like a throttle or an accelerator pedal in a car, but instead simply turns the A/C on or off. It matters to know this, because the tendency otherwise may be to turn the thermostat way down in an effort to cool the house quickly, then forget to adjust it later on. The A/C ends up running and running, attempting to cool the house to a temperature lower than you actually want or need. The best thing to do is set the thermostat at the temperature you want. The house will cool just as quickly.
A central A/C unit typically draws a whopping 3500 watts of energy while on. I've come to associate the hum of the A/C with the blowing up of mountaintops in West Virginia, which may be the source of coal used to generate those watts. Most people are oblivious to such dramas hidden behind the facade of everyday domestic life.
The second thing to know is that ceiling or floor fans, which only use 20 or 30 watts of electricity while running, can help you cut back on A/C use. What we've found, as we progressively try to trim the use of A/C in the house, is that it's possible to gain enough comfort on hot days by using a mix of ceiling fans and A/C, with the A/C on just enough to lower the humidity in the house. Of course, when the A/C is running, all the windows have to be closed. Otherwise the heat and humidity from outside just pours right back in.
Our central A/C system, while not the worst, is not exactly state of the art. It pushes coolish air through a labyrinthine system of ducts, and sometimes labors to bring the house temperature down below a certain point. With the thermostat set at 81 on a 95 degree day, it cuts the humidity nicely, then turns off. The fans do the rest. Set it at 78 and it may lumber on for long periods without achieving much gain in comfort. Some may think 81 sounds a tad high, but fans are said to make it feel 4 degrees cooler, and over time our bodies have grown accustomed to a broader range of temperatures. A little bit of adaptation now could save a lot of adaptation later on.
A couple degrees adjustment of the thermostat, then, can make a big difference in how much the A/C runs. If it's running constantly, try nudging the thermostat upwards to give the A/C, and the planet, some relief. Wear shorts and t-shirt, or something similarly light, and let the fans do the rest.