One kilowatt-hour equals how many watt-hours?

• A. 1,000 watt-hours
• B. 100 watt-hours
• C. 1 watt-hour
• D. 10,000 watt-hours

Answer: (A)

Power times time equals energy, and a watt-hour is the energy of one watt sustained for one hour. A kilowatt is 1000 watts, so a kilowatt-hour is 1000 W × 1 hour, which equals 1000 watt-hours. The other values would correspond to different amounts of energy—for example, 1 Wh is 0.001 kWh, and 10,000 Wh is 10 kWh.