Which unit is larger: watt-hour or kilowatt-hour?

Which unit is larger: watt-hour or kilowatt-hour?

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

Answer: (D)

Understanding energy units and how prefixes scale their size is what this question tests. A watt-hour is the amount of energy from one watt used for one hour. A kilowatt-hour is the energy from one kilowatt (which is 1000 watts) used for one hour. Since the power is 1000 times larger, the kilowatt-hour is 1000 times bigger than a watt-hour. In common terms, 1 Wh equals 3600 joules, so 1 kWh equals 3.6 million joules. That shows why the kilowatt-hour is the larger unit. (For perspective, a joule is a much smaller energy unit, so it’s not on the same scale as these hour-based energy units.)

Understanding energy units and how prefixes scale their size is what this question tests. A watt-hour is the amount of energy from one watt used for one hour. A kilowatt-hour is the energy from one kilowatt (which is 1000 watts) used for one hour. Since the power is 1000 times larger, the kilowatt-hour is 1000 times bigger than a watt-hour. In common terms, 1 Wh equals 3600 joules, so 1 kWh equals 3.6 million joules. That shows why the kilowatt-hour is the larger unit. (For perspective, a joule is a much smaller energy unit, so it’s not on the same scale as these hour-based energy units.)