Some characters have powers that when used in excess, whether in duration or overall exertion effort, cause themselves to be unable to use their power for a period of time. They may need to replenish through an activity, food, or regenerative process. Atom Eve's transmutation powers require she absorb any unused atoms into her body, which must later be eliminated from her system as waste. She claims that on days when she uses her powers a lot she can "go to the bathroom" six or seven times.
This can be confused with Power Loss which is when a character can lose control of their power for various reasons including external forces and lack of concentration. Power Depletion is the act of overusing a power demanding a recharge.