Energy Consumption

Electrical energy is the amount of work a device uses up while it runs. Since power tells you how fast energy is being used, multiplying power by the time gives the total energy consumed. This is why a higher-power appliance uses more energy in the same time, and why even a low-power device can use a lot if it runs for many hours.

Use this formula when you want to calculate how much electrical energy an appliance, machine, or system uses over a period of time. It is common in electricity bills, energy audits, and environmental studies of household or industrial power use.

• Using watts and hours but forgetting to convert to kWh when needed
• Mixing up power and energy: power is the rate of use, energy is the total used
• Using minutes or seconds in time without converting them to matching units