Tesla CEO Elon Musk speaks at the company's Battery Day event.Tesla/Youtube Replacing an electric car's battery can cost thousands of dollars. Luckily, most batteries last up to 200,000 miles and technology is constantly improving. Tesla guarantees its batteries for eight years or 100,000-150,000 miles, whichever comes first. A big concern for prospective Tesla owners is whether the battery will need replacing.EV battery replacement could cost anywhere from $5,000 to $20,000, according to Recurrent.