A 1500 watt heater runs for 2 hours. How much energy does it use?

Correct answer to question 12 (Electronics Information): 3 kilowatt-hours

Method

Convert watts to kilowatts first: 1500 watts is 1.5 kilowatts, and running for 2 hours uses 1.5 x 2 = 3 kilowatt-hours. Forgetting to convert leaves the answer a thousand times too large.