From The American Council for an Energy Efficient Economy
Reduce Your Need For Air Conditioning
Before you consider upgrading your cooling equipment, the cheapest way to save money and energy from cooling is to reduce the need for mechanical air conditioning in the first place. This can be done in several ways (follow the links to learn more):
1. Insulate and tighten your house
Improving insulation and air sealing prevents heat from entering your house. Your highest priority should be to check insulation levels and air leaks between your living space and the attic.
2. Get rid of inefficient appliances
Inefficient appliances give off a lot of heat. Especially consider replacing or discarding old or auxiliary refrigerators; replace incandescent light bulbs with fluorescents; and unplug electronic equipment when not in use.
3. Consider "cool" exterior finishes
When replacing your roof or painting your house, using light-colored or other "cool" roofing and siding products can reduce your peak cooling demand by 10-15%. There are a number of roofing products that can dramatically cut down on heat gain without blinding the neighbors. Start by looking for ENERGY STAR Reflective Roof Products.
4. Shade or improve windows
To keep high-angle summer sun out, consider horizontal trellises for your east and west-facing windows. Protect south-facing windows with deciduous trees or climbing foliage so you can take advantage of low-angle sun in the winter, when the leaves fall. New windows on those walls that get the most summer sun should have low-e glazings to block unwanted heat gain.
5. Cool with air movement and ventilation
Fan operation uses less energy than air conditioning and can be adequate for attaining desired comfort levels unless you live in a very humid climate.
Ceiling fans. Ceiling fans cool by creating a low-level “wind chill” effect throughout a room. As long as indoor humidity isn’t stifling, they can be quite effective. Just remember that a fan cools people — it doesn’t actually reduce room temperature — so turn it off when you leave the room. Look for ENERGY STAR rated ceiling fans.
House fans. Unless you live in a very humid climate, installing a large fan in your top-floor ceiling is a very effective way of cooling your whole house down without central AC. These fans suck air through the house, inducing a strong draft in rooms where windows are open as it pulls cooler, outdoor air inside. Check with your local home improvement retailer about available products and installation.
A room air conditioner's efficiency is measured by the energy efficiency ratio (EER). The EER is the ratio of the cooling capacity (in British thermal units [Btu] per hour) to the power input (in watts). The higher the EER rating, the more efficient the air conditioner.
National appliance standards require room air conditioners to have an energy efficiency ratio (EER) ranging from 8.0–9.8 or greater, depending on the type and capacity, and ENERGY STAR qualified room air conditioners have even higher EER ratings.
The Association of Home Appliance Manufacturers reports that the average EER of room air conditioners rose 47% from 1972 to 1991. If you own a 1970's-vintage room air conditioner with an EER of 5 and you replace it with a new one with an EER of 10, you will cut your air conditioning energy costs in half.
When buying a new room air conditioner, look for units with an EER of 10.0 or above. Check the EnergyGuide label for the unit, and also look for room air conditioners with the ENERGY STAR® label.