Window AC Units: Wattage Use

Wattage Range

• Air conditioning units have a wide range of wattage use. For window units, these range from 500 to 2,000 watts, according to "Black & Decker The Complete Guide to Home Wiring: A Comprehensive Manual, from Basic Repairs to Advanced Projects." Each air conditioning unit will have the wattage on the energy facts sticker on the package or on a plate directly on the unit.

Window Versus Central Usage

• Compared to central air conditioning units, window units use less power. Central air conditioners require between 2,300 and 5,500 watts. Central units might be a lower-cost option than window air conditioners if you have several rooms to cool.

EER and Wattage

• The wattage of an air conditioner is tied to its energy efficiency rating. To calculate the EER, divide the BTUs per hour of cooling by the wattage used by the air conditioner. For air conditioners, the outside temperature makes a difference in the number of BTUs of cooling and the wattage used. When finding the EER, both the BTUs and wattage used for the calculation must be for the same outside temperature. The most efficient models will have high EER ratings.

Voltage and Wattage

• Voltage and wattage are linked together. This will help you to determine the type of outlet you can use to plug in your window air conditioner. Most window AC units will use a 120-volt outlet, but high wattage units will require a dedicated 240-volt appliance outlet. Divide the number of watts of your window air conditioner by the amps in the circuit it is plugged into. If that number is greater than 120, you will need to plug in the air conditioner into a 240-volt appliance outlet. For instance, if you have a 2,000-watt air conditioner plugged into a 15-amp breaker, divide 2,000 by 15 for 133 volts. Since this is greater than the 120 volts of the outlet, you would need a separate 240-volt outlet to plug in the air conditioner.