I have read articles that tell folks to unplug chargers when not in use, saving the electricity they consume. Upon reading your comment on same topic, I finally got off my a$$ to compute the cost...
- Assuming 10 idle chargers left idle for 14 hours each day, if they consume 0.002A (or 0.25W, a generous assumption if they are charging nothing) per hour, over the course of a month they collectively use a wasted 2.8 cents per month (assuming $0.30 per kiloWatt-hour).