Your air conditioner is designed to keep you cool all summer, even when the electric bill arrives. Here are a few tips you can use to save on cooling costs: If you don't mind indoor temperatures that are a little warmer, a thermostat setting of 78 degrees can save as much as 25 percent over the typical setting of 72. When you leave the house for more than four hours, increase the thermostat setting, but don't turn the unit off entirely. Once the inside temperature gets too high, it takes a lot of energy to bring it back down. Some air conditioning is also necessary to retard mold and mildew during hot, humid weather. If you're shopping for a new air conditioner, take note of the Energy Efficiency Rating listed on appliances. A rating of 9 or more is considered good. Keep your unit running at peak efficiency. Change the filter at least once a month, and don't let plants or fallen leaves block circulation to the outdoor unit. It's a good idea to have your air conditioner cleaned and oiled professionally before summer begins. Close your blinds and curtains during the hottest part of the day to block part of the sun's heat. Avoid using appliances that create heat. Use the microwave instead of the range, or fire up the outdoor grill. Dry your clothes on lines, if possible, or run the dryer in the evenings when it's cooler. When you don't need air conditioning, don't use it. Open the windows on cool mornings. A fresh breeze can improve the quality of your indoor air, as well as hold down energy costs.