It might surprise you to know that buying a bigger room air-conditioning unit won't necessarily make you feel more comfortable during the hot summer months. In fact, a room air conditioner that's too big for the area it is supposed to cool will perform less efficiently and less effectively than a smaller, properly sized unit. This is because room units work better if they run for relatively long periods of time than if they are continually, switching off and on. Longer run times allow air conditioners to maintain a more constant room temperature. Running longer also allows them to remove a larger amount of moisture from the air, which lowers humidity and, more importantly, makes you feel more comfortable.
SEER is the Seasonal Energy Efficiency Rating. SEER rates the efficiency during the cooling season. Look for a SEER rating of 13 or above.
Evaporative coolers may be installed as an alternative to air conditioning, particularly in climates with very dry air. Evaporative coolers provide mechanical cooling to a building by either direct contact of air with water (direct evaporative cooler) or a combination of a first-stage heat exchanger to pre-cool the air and a second stage with direct air contact with water (indirect/direct evaporative cooler).
Tips for Lowering Your Central Air Conditioner's Energy Usage
Whole house fans help cool your home by pulling cool air through the house and exhausting warm air through the attic. They are effective when operated at night and when the outside air temperature is cooler than the inside.
Set your thermostat at 78ºF or higher. Each degree setting below 78ºF will increase energy consumption by approximately 8%. Be careful, however, that if you're A/C is oversized the diminished run-time from raising the thermostat setting may result in too-high indoor humidity in some locations.
Don't set your thermostat at a colder temperature 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 in very humid weather. When it's humid set the fan speed on low. You'll get better cooling.
Consider ceiling fans to spread the cooled air more effectively through your home without greatly increasing your power use.
Don't place lamps or TV sets near your air conditioning thermostat.
Plant trees or shrubs to shade air-conditioning units but not to block the airflow. A unit operating in the shade uses as much as 10% less electricity than the same one operating in the sun.
Use bath and kitchen fans sparingly when the air conditioner is operating to avoid pulling warm, moist air into your home.
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 will need a service contractor to check the fluid and adjust it appropriately.
Shade east and west windows.
When possible, delay heat-generating activities, such as cooking and dishwashing, until evening on hot days.
Keep the house closed tight during the day. Don't let in unwanted heat and humidity. Ventilate at night either naturally or with fans.