There are different sizes, but on average they use 2 Amp, which - at 110 Volts - equals 220 Watt. But the pump wouldn't run all the time (unless you have a serious flooding problem which should be addressed at the source, not "pumped away"). A float switch inside the pump turns it on when the water level reaches a certain height, and off when the water is gone. I would say, money-wise and over time, it costs you as much as a standard light bulb. https://answers.yahoo.com/question/index?qid=20061004073449AAMBLTy