Idle phone charger draws 0.1–0.5 W — is it worth unplugging?

Measurements show that a phone charger left plugged in without a device draws between 0.1 and 0.5 W in standby mode. Over a year of average use, this translates to a few kilowatt-hours and a small addition to the electricity bill. Unplugging chargers after use is a good habit, though the financial savings are modest.