Set your thermostat at 78ºF or higher. Each degree setting below 78 ºF will increase your energy consumption by approximately 8 percent.
Use bath and kitchen fans sparingly when the air conditioner is operating.
Inspect and clean both the indoor and outdoor coils. The indoor coil in your air conditioner acts as a magnet for dust because it is constantly wetted during the cooling season. Dirt build-up on the indoor coil is the single most common cause of poor efficiency. The outdoor coil must also be checked periodically for dirt build-up, and cleaned if necessary.
Check the refrigerant charge. The circulating fluid in your air conditioner is a special refrigerant gas that is put in when the system is installed. If the system is overcharged or undercharged with refrigerant, it will not work properly. You may need a service contractor to check the fluid and adjust it appropriately.
Reduce the cooling load by using cost-effective conservation measures. For example, effectively shade east and west windows. When possible, delay heat-generating activities, such as dishwashing, until the evening on hot days.
Keep the house closed tight during the day over most of the cooling season. Don't let in unwanted heat and humidity. If practical, ventilate at night either naturally or with fans.
Don’t use a dehumidifier: Try not to use a dehumidifier at the same time your air conditioner is operating. The dehumidifier will increase the cooling load and force the air conditioner to work harder.
If your home has Room Air Conditioning:
Keep the unit leveled when installing, so that the inside drainage system and other mechanisms operate efficiently. If possible, install the unit in a shaded spot on your home's north or east side. Direct sunshine on the unit's outdoor heat exchanger decreases efficiency by as much as 10 percent. You can plant trees and shrubs to shade the air conditioner, but do not block the airflow.
Don't place lamps or televisions near your air-conditioner's thermostat. The thermostat senses heat from these appliances, which can cause the air conditioner to run longer than necessary.
Set your air conditioner's thermostat as high as is comfortably possible in the summer. The less difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be. And don't set your thermostat at a colder setting than normal when you turn on your air conditioner. It will not cool your home any faster and could result in excessive cooling and, therefore, unnecessary expense.
Set the fan speed on high, except on very humid days. When humidity is high, set the fan speed on low for more comfort. The low speed on humid days will cool your home better and will remove more moisture from the air because of slower air movement through the cooling equipment. Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air more effectively through your home without greatly increasing electricity use.
Ensure proper maintenance of your air conditioner to save energy. Be sure to do the following:
At the start of each cooling season, inspect the seal between the air conditioner and the window frame to ensure it makes contact with the unit's metal case. Moisture can damage this seal, allowing cool air to escape from your house.
Check your unit's air filter once a month, and clean or replace filters as necessary. Keeping the filter clean can lower your air conditioner's energy consumption by 5 percent to 15 percent.
Occasionally check the unit's drain channels. Clogged drain channels prevent a unit from reducing humidity, and the resulting excess moisture may discolor walls or carpet.