Question

Kilowatt is the unit of electrical _____ but kilowatt-hour is the unit of electrical _____.

• A. power
• B. energy

Answer 1

Power:

1. Power may be defined as the rate of doing work in unit time.
2. The unit of power is Watt ($W$) which is equal to joules per second ($\raisebox{1ex}{$J$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$).

Energy:

1. It is defined as the capacity to do work, such as the capacity to move an object (of a given mass) by the application of force.
2. Joule is the SI unit of energy.

Explanation:

1. In SI system, the unit of power is the watt $\left(W\right)$, Kilowatt is equal to one thousand $\left({10}^3\right)$ watts.
2. The kilowatt-hour $\left(kwh\right)$ is a unit of energy and is equal to one thousand $\left({10}^3\right)$ watt-hours.
3. If the energy is being transferred or used at a constant rate (power) over a definite period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time in hours.

Hence, kilowatt is the unit of electrical power but kilowatt-hour is the unit of electrical energy.