If you leave your charger plugged into the outlet without a device connected to it, it will, in most cases, consume a very small amount of power. This amount of power, also known as standby consumption, can however add up if it remains on unnecessarily for a long period of time.

The exact amount of costs depends on the energy price per kilowatt-hour (kWh) and the duration of the unnecessary power consumption. In general, you can expect the consumption of a charger not in use to have a negligible effect on your energy bill. Nevertheless, it is still a good habit to unplug chargers when they are not in use, both to save energy and to reduce potential safety risks.