🔋 Watt-hour Calculator
Calculate how much energy a device uses in watt-hours and kilowatt-hours, and estimate the electricity cost.
What is a watt-hour?
A watt-hour (Wh) is a unit of energy equal to one watt of power sustained for one hour. It’s the standard way to describe how much energy an appliance or device actually consumes over time, as opposed to watts, which only describe its instantaneous power draw. 1,000 Wh equals one kilowatt-hour (kWh), the unit most electricity bills are based on.
How this calculator works
The calculator multiplies the power draw per device by the number of hours used and the number of devices: Energy (Wh) = Power (W) × Time (hours) × Quantity. It then converts that to kWh and, if you enter your electricity rate, estimates the cost using Cost = kWh × Rate. A rough 30-day monthly estimate is also shown assuming the same daily usage pattern repeats.
This tool is for general planning and educational purposes. Actual utility bills depend on your specific rate plan, taxes, and fees, which can vary by provider and time of use.