Energy spent on the air conditioner can take up a significant chunk of your energy bill.  It is not easy to calculate the energy use by the central air conditioner, because it depends on the climate you live in, the thermal insulation of your house, the air conditioner type and its efficiency.  But, nevertheless following these guidelines will help reduce your air conditioner’s energy use:

• Set thermostat at the highest possible temperature that meets your comfort level.  The smaller the temperature difference between the outside and the inside, the less energy it would take to cool down the inside.  For better efficiency, it is recommended to set your thermostat at 78F (26C) or higher.
• Run a ceiling fan when you‘re in the room.  Ceiling fans use a small fraction of energy compared to the air conditioner and they do help with cooling you down. Don’t forget to turn the fan off when you leave the room, remember, the don’t cool the room, they move the air around to make you feel cooler.
• Raise thermostat’s temperature if you’re leaving the house for over 4 hours.  If you have a set schedule every day, it might be good to invest in a programmable thermostat, so you don’t have to worry about remembering to reset the temperature every time you leave the house for extended period of time.
• Keep your blinds or curtains closed, if you are not home.   This will eliminate additional heat coming in through the windows.
• Avoid use of heat-generating appliances like the clothes dryer, oven, kitchen stove, dishwasher during the hottest part of the day.  They will make your air conditioner work harder.
• And last, but not least, change your air filters regularly.  Air conditioning unit re-uses the air over and over, so when the cool air comes in, the hot air has to make its way back out to the heat exchanger through the ducts with the air filters on them.  If the filters are clean, the air will leave easily.  If the filters are dirty, the system will have to work harder to bring back the used air.  This will reduce the efficiency of the air conditioning unit.  Which reminds me, I have to check my air filters!