Chargers, and other appliances plugged in but not in use, draw power. It is certainly less than when in use, but it adds up. This is often referred to as 'phantom power usage'. If you touch your phone chargers when they are plugged in, you'll feel the heat generated by the electricity.

Our power company recommends plugging chargers, computers, etc. into power strips. When you turn the power strip switch off, there is no power drawn.

HTH.