It may be cheaper to shut off your air conditioner at night, if your house has good ventilation and the outdoor temperature cools down. Switch the AC back on during the day. Make sure you close all windows and doors to the outside. It may take some time to bring the indoor temperature to the setting you want, especially on hot mornings. Another way to save money is to keep the air conditioner on but set the thermostat at higher temperature, say 80 degrees.