How is a kilowatt-hour defined?

A kilowatt-hour is defined as a unit of energy that represents the amount of energy consumed when a power of one kilowatt is used for one hour. This means if you run a device that uses power at a rate of one kilowatt for an entire hour, the total energy consumption for that period is one kilowatt-hour. This measurement is particularly useful for understanding electricity usage in households and businesses, as it allows consumers to quantify the energy they consume over time in a straightforward manner.

In this context, other options do not accurately define a kilowatt-hour. One watt used for one hour does not equate to a kilowatt-hour since it is a much smaller energy measurement. Voltage over time does not pertain to energy consumption, and resistance is a distinct electrical characteristic that relates to the opposition to current flow, not energy. Thus, focusing on the concept of power and duration indicates that choice B encapsulates both the measurement of power (in kilowatts) and the time it is used (in hours), accurately defining a kilowatt-hour.