What is the unit commonly used to measure electrical energy consumption by utilities?

• A. Kilowatt-hour
• B. Joule
• C. Watt
• D. Volt

Answer: (A)

Electrical energy consumption is about how much energy is used over a period of time, not just the immediate power level. Utilities bill based on energy used, which means we need a unit that combines power and time into a single amount. The kilowatt-hour does just that: one kilowatt-hour is the energy used when a device drawing one kilowatt runs for one hour. For example, a 1 kW heater running for two hours uses 2 kWh of energy, which equals 7.2 million joules. The joule is the fundamental energy unit, but it's too small for typical home usage and isn’t convenient for billing. The watt measures power (the rate of energy transfer), not total energy over time, and the volt is a measure of electrical potential, not energy consumption.