Comparison of 220 & 120 Volt Air Conditioners

Voltage Sizes

• The standard electrical outlet in most homes accepts 120-volt air conditioners as well as air conditioners labeled as 110- or 115-volt. Most plugs have the usual two prongs, with a third, round grounding prong. Plugs for 220-volt air conditioners may look like larger versions of the standard plug but usually have a different prong-and-receptacle configuration, much like the plugs and outlets for other heavy-duty appliances like stoves and clothes dryers. While 120-volt air conditioners simply plug into existing sockets, you may have to add a wall socket that can accept the 220-volt air conditioner's plug. This requires new wiring from the wall to the breaker box, and a circuit designed to handle the electrical load. Unless you are very handy with electricity, call a professional to do this wiring for you.

Btu Per Hour

• Btu, or British thermal units, are the measure of the air conditioner's cold air output. Most air conditioners that plug into standard wall sockets deliver less than 15,000 Btu per hour. Air conditioners that produce more than 15,000 Btu per hour require a 220-volt wall receptacle.

Room Size and Voltage Choices

• Calculate the square footage of the room where the air conditioner will go. For a square or rectangular room, multiply the width by the length of the room. If the room is triangular, multiply the length by the width and divide the result by two. Once you determine how many Btu per hour you need for a specific room, you will know whether you need a 120-volt or a 220-volt window unit. Check the wall outlets where the unit will be installed to be sure they are the proper voltage. Because the plugs and wiring can get hot, avoid using extension cords with window air conditioners.

Efficiency and Size

• New window air conditioners carry labels that provide the seasonal energy efficiency ratio. Choose an air conditioner with the highest SEER rating you can find. The air conditioner's label should also give the number of Btu and what size room the unit can cool. The latter is a general figure, since factors such as whether the unit is installed in a sunny or shaded window, which direction the window faces and the climate where you live affect the unit's efficiency.