A Toyota Prius battery warranty is a good idea if you plan to drive a Prius. The warranty offered by Toyota is considered the best, as compared to warranties offered for other hybrid vehicles. The warranty runs for a period of eight (8) years or 100,000 miles, whichever comes first. During that period, the battery will be replaced should anything go wrong with it. Of course, you must take the vehicle to a Toyota dealership, because there are no outside companies that provide this service. California residents have warranties that run for ten (10) years and 150,000 miles, whichever comes first.