How are kilowatt-hours determined?

• A. By dividing watt-hours by hours.
• B. By multiplying the number of kilowatts (kW) required by the number of hours of use.
• C. By measuring the voltage and current.
• D. By adding the kilowatts and the hours.

Answer: (B)

Kilowatt-hours are a measure of energy used over time. To determine them, multiply the power in kilowatts by the time in hours. This works because energy equals power times time. For example, a 1 kW device running for 1 hour uses 1 kWh of energy, and a 0.5 kW device running for 2 hours also uses 1 kWh.

Dividing watt-hours by hours would give watts, which is instantaneous power, not energy. Measuring voltage and current gives power, not the total energy consumed unless you also account for time. Adding kilowatts and hours mixes units that don’t combine to a meaningful energy value.