Do your meter and utility bill match up?
Utility workers make mistakes just like the rest of us, and when they make mistakes reading your meter, it can be costly. While you'll probably notice a big error on your utility bill, you may not catch more subtle errors.
Make sure you're only getting charged for the electricity you actually used by comparing the meter reading on your utility bill to what you actually see on your meter. If the amount on your meter is lower than the one on your bill, that's a dead giveaway that you're being overcharged.