One kilowatt hour of electrical energy equals how many joules?

1. Energy is power times time, E = P t. 2. One kilowatt is 1000 W, and one watt is one joule per second. 3. One hour is 60 times 60 = 3600 s. 4. So 1 kW h = (1000 J/s)(3600 s). 5. Multiplying gives 3.6 x 10^6 J. 6. 3.6 x 10^3 J is the value for one watt hour, the trap of dropping the kilo prefix. 7. 6.0 x 10^4 J would follow from using 60 s for an hour rather than 3600 s. _Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section The Cost of Electricity_