Tips for Buying an Air Conditioner

If your air conditioner is more than eight years old, it's time to buy a new one, according to National Geographic's Green Guide.

Here's an Air Conditioner Buying Guide that explains BTUs, Energy Star Rating and Energy Efficiency Ratio.

Consumer Reports Air Conditioner Buying Guide includes information on size, noise, warranty and other considerations.

Home Energy Saver offers the following tips if you plan on using a contractor to install an air conditioner:

• Don't hire a contractor who wants to size your unit based solely on the floor area of your house. Contractors should calculate how much cooling a home needs according to the guidelines set forth in the Manual J of the Air Conditioner Contractors of America (ACCA). To gather the necessary information, your contractor should spend about an hour poking around your house, taking measurements in each room and asking questions. He or she needs to measure floors, ceilings, and walls—including all the windows—and check insulation in the attic, walls, and crawlspaces. Some other factors that go into the cooling load formula include indoor and outdoor temperatures, number of occupants, shading, and roof color.

• Insist on getting a copy or computer printout of the cooling load calculations. These can be useful in comparing bids from contractors. Question the contractor if the calculations don't include all the items mentioned above, or if you see anything that you don't understand.

• Ask your contractor to size the air conditioner based on the latent cooling load (which considers the humidity of the air) as well as the sensible cooling load (which considers the temperature of the air) for your home.

• Don't be tempted by the lowest bid. Be willing to pay for the time the contractor must spend to do the job right.

• Check for duct leaks and disconnected ducts. Also be sure air flow is not restricted by ducts that are crushed or too small for the system. Ideally, the contractor should use diagnostic equipment to find leaks and then fix them with quality duct sealants (not duct tape). It doesn't make a lot of sense to buy a larger air conditioner to cool your attic or crawlspace!

• Buy a high-efficiency unit. New air conditioners are required by federal law to have a SEER of 13 or higher. Even though it will cost more, it's usually worth it to buy at a unit exceeding this value because over time that initial investment will be paid back with energy savings. Look for an ENERGY STAR label when you shop. If you are replacing an existing air conditioner, you must replace the whole unit, including the inside coil and often the blower fan, to achieve the rated efficiency. [Information in this paragraph updated by LBNL to reflect new standards of January 2006]

• Install for ease of maintenance. Make sure the inside coil can be reached for cleaning. The contractor may have to install an access panel, depending on the model. The coil should be cleaned every two years. The air filter should be located where it is easy to remove. Check it every month during the summer, and clean it or change it whenever it is dirty.

• Place the outside unit on the north or east side of the house, out of direct sunlight, but don't add shade for it. Leave plenty of room for free air flow on all sides, and leave at least 4 feet of clearance at the top. Keep the area free of debris and shrubbery. The air conditioner draws a lot of air through it. It's more important for the unit to have a lot of space than for it to be well shaded.