Do not confuse power (Watts) and energy (kWh=kilowatt hour). Power is displayed on a label attached to the device. But on the electricity bill, it is the energy used that is charged for. The energy E is linked to the power P by the formula:

P = E / t

t represents the duration of use (expressed in hours).

A device may indicate a high power but have low energy consumption over a year if not used much. An iron could be like this.

Conversely, some devices whose label indicates low power such as a lamp or refrigerator can be expensive users of energy because they are used frequently and over long periods.