Power is a rate. Energy adds up over time.
A watt (W) measures the rate at which an appliance uses electrical energy. A kilowatt is 1,000 watts. A kilowatt-hour (kWh) measures the energy used by one kilowatt operating for one hour.
A kettle and a lamp can tell different stories.
A 2,000 W kettle running for six minutes uses 0.2 kWh: 2 kW × 0.1 hours. A 60 W lamp used for four hours uses 0.24 kWh. The lamp draws much less power, but its longer operating time makes the energy use in this example slightly higher.
At an example rate of USD 0.25 per kWh, those uses cost USD 0.05 and USD 0.06 respectively. These are illustrative inputs, not device specifications or a suggested electricity tariff.
Rated watts are only one piece of the picture.
Some appliances draw a fairly steady amount while operating. Others switch on and off, change speed, or heat only during part of a cycle. Multiplying a maximum rating by every hour the appliance is plugged in can substantially overstate use.
For those appliances, use measured kWh over a representative period, or energy label data that matches your usage. Include standby consumption in a measured period if you want it included; the calculator does not add a hidden standby allowance.
How to enter the information you have
- Power and time: enter watts or kilowatts and actual operating hours.
- A meter reading: enter kWh and the number of days measured.
- An annual label: enter its kWh as a yearly figure.
- A cycle label: use the per-cycle input, including a per-100-cycles option.
Check the time period before comparing.
One appliance’s daily kWh is not directly comparable to another’s yearly kWh. PlugMallow scales inputs to a 365-day year, then divides by 12 for an average month. This is a consistent annual estimate; it does not predict seasonal peaks.
Further reading: Australian Government: energy rating. Formula details: PlugMallow methodology.