The Basics:
Air Conditioners
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When shopping for a room air conditioner, it is important to choose a unit with enough cooling capacity for your space without getting one that is too large for your needs. A too-small unit won't cool the room enough. A too-large unit will waste energy and won't dehumidify the room properly. As a rule, it is better to buy several small units than to use one large air conditioner to cool several rooms.
If the area you need to cool is small, 150 square feet or less, the cooling capacity you need to get is 4,000 to 5,000 Btu. From 150 to 250 square feet, you need 5,000 to 6,000 Btu of cooling capacity.
If you are cooling from 250 to 450 square feet, you need 6,000 to 8,500 Btu of cooling capacity. If you are cooling from 450 to 600 square feet, you need 8,500 to 11,000 Btu. If you are cooling from 600 to 900 square feet, you need 11,000 to 14,000 Btu. And if you are cooling from 900 to 1,200 square feet, you need 11,000 to 15,000 to 19,000 Btu of cooling capacity.
The majority of air conditioners are designed to be installed in conventional single- and double-hung windows (which open up from the bottom). Some models can also be installed in sliding windows as well. Air conditioners cannot be installed in casement or louvered windows. Measure your window before you go shopping for an air conditioner. All units have accordion-like wings that pull out sideways to seal the space between the air conditioner and the window frame.
Most units can also be installed through a wall. In a room with only one window, this might be the only way you can have cooling as well as the use of the window. Through-the-wall installation means cutting a suitable size hole in the wall and exterior siding, then adding a frame to support the unit. Through-the-wall installation is a lot of work, and might not be suitable for all types of homes (brick or masonry, for example) but it offers quieter operation and more secure installation. You'll have less air leakage in a through-the-wall installation, making your unit more effective in the summer and keeping the warm air in during the winter. If you are handy, consider doing the work yourself. If not, get a few estimates for the work from licensed contractors. In most cases, the work can be completed in about half a day.
Air conditioners are not maintenance free. Clean the foam filter in the front of the unit at the beginning of the season and at least once a month. Simply remove the filter, rinse it under running water, let it dry, and reinstall. The exterior fins perform the actual heat exchange and should be kept as clean as possible. These fins are thin metal and bend easily so work carefully when dusting. If any of the fins become bent, carefully straighten them out with a piece of rigid plastic, such as a credit card. Rinse the fins on the exterior of the unit as well. Use a garden hose or bucket of water to remove spider webs, dust, and any other airborne debris.
How to Shop
When shopping for a room air conditioner, pay attention to the unit's plug, as well as the kind of outlet you are planning to use to run the unit. In addition, make certain that the circuit can run the unit; smaller room air conditioners run on standard 115-volt circuits, while larger ones may need dedicated circuits or a 230/208-volt circuit.
You should also pay close attention to the large yellow Energy Efficiency Ratio (EER) stickers on the fronts of the units. Since January 1, 1990, the Federal government has required all room air conditioners to have an EER of at least 8.0. The EER is computed by dividing cooling capacity by the watts of electricity used. The higher the EER, the more efficient the room air conditioner, and the less it will cost to operate.
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