### Kilowatt Hours

To measure the electricity used by a large appliance over time, use kilowatt hours. You may recognize the unit from your electricity bill; a kilowatt equals one hour of continuous electricity usage at a rate of 1000 watts. A single household typically uses 1,079 kilowatt hours annually for its clothes dryer alone, which works out to 65.9 billion kilowatts per hour (kwh), per year used by clothes dryers, or 5.8 percent of total household power usage. Compared with other major appliances, electric dryers use less electricity than refrigerators or lighting, which use around 14 and 9 percent of total household electricity respectively. They use more than freezers or televisions, which each consume 3 percent.

### Volts

Whereas watts measure the flow of energy (in joules) over time (per second), you can understand volts as the "pressure" of the electricity. Volts relate to amperes, the flow of electricity, by Ohm's Law. Volts are equal to amperes times ohms, the measure of resistance. In other words, a flow of electrical charge that encounters resistance will produce volts. For practical purposes, most large appliances require either 110 to 120 or 220 to 240 volts. An electric dryer typically uses 220 to 240 volts with a 30 amp breaker. You can compare this with a gas-powered dryer, which only uses a 110 to 120 volt circuit, with a 15 amp circuit breaker. More specifically, an electric dryer requires only 120 volts for its timer and motor mechanisms; however, to operate the heating element, an electric dryer requires the full 240 volts.

### Energy Factor Requirements

To contextualize your electric dryer's power requirements in terms of efficiency, you can use its energy factor (EF). The EF measures pounds of clothing dried per kilowatt-hour of power used. The federal standard for an electric dryer's minimum EF is 3.01. Gas dryers have a slightly lower minimum standard at 2.67. An electric dryer meeting the minimum of 3.01 EF, and using 1,079 kilowatt-hours in one year, will dry 3,248 lbs. of laundry per year, or around 62 lbs. per week. Generally, an electric dryer's EF increases if it has moisture sensors to regulate the cycle's end.