What Grade of Electrical Extension Cord Should I Use for a Window A/C Unit?

Plug Type

• An A/C unit typically has a three-prong plug; the third prong provides a connection to the home’s grounding wire. The grounding wire helps reduce the risk of fires and electrical shock. A three-prong plug should be used only with a three-prong extension cord and plugged into a three-prong outlet.

Power Requirements

• Check the label on the A/C unit or its manual for the unit's energy requirements. All extension cords have a maximum amp rating; this is the maximum number of amps it can handle safely. Sometimes the power rating is listed in watts. To convert watts to amps, divide the number of watts by 110. For example, if the A/C unit uses 1,000 watts, its amp usage = 1,000/110 = 9.09 amps. Always round the calculation up. In this example, the amp usage is 10.

Gauge

• The gauge of an extension cord is a measurement of the diameter of the wire inside. The larger the diameter of the wire, the more current it can handle. The lower the number, the thicker the wire and the higher the cord’s ability to deliver the current. Read the label on the extension cord to determine the gauge. Cords of the same thickness can have different-sized wires inside and, therefore, have different gauge ratings.

Length

• Use an extension cord that is only as long as you need. The longer the cord, the higher the electrical resistance and the less power the cord will deliver to the unit.

Determine the Right Cord

• The right extension cord is a combination of length, gauge and power requirements. In general, a 16-gauge extension cord up to 100 feet in length can handle loads of 10 amps. A 14-gauge 50-foot cord can safely handle the power requirements of units that require 10 to 15 amps. Read the extension cord label carefully to confirm that it will safely handle the power requirements for the A/C unit.