Electric energy is usually expressed in _______, and power is expressed in ______

• A. amps, kilowatt-hours
• B. kilowatt-hours, watts
• C. volts, amps
• D. watts, amps

Answer: (B)

Electric energy is the total amount of energy used over a period, while power is the rate at which that energy is used at any moment. In everyday electrical use, energy is expressed in kilowatt-hours because it captures consumption over time, and power is expressed in watts (or kilowatts) because it’s a rate. A kilowatt-hour is the energy used by a 1-kilowatt device running for one hour (1 kW × 1 h = 1 kWh), so a 2 kW appliance running for 3 hours consumes 6 kWh of energy. The rate at which it uses energy is 2 kW, which is 2000 watts. Therefore, energy is expressed in kilowatt-hours and power in watts. Ampere and volt are current and voltage, respectively, and do not express energy or power, so they don’t fit the pairing.