"Multiple years" on 6xAA (or there's a wired version with 3xAA as back up) according to http://www.theverge.com/2013/10/8/4790896/nest-protect-smoke-detector ht

"Multiple years" on 6xAA (or there's a wired version with 3xAA as back up) according to http://www.theverge.com/2013/10/8/4790896/nest-protect-smoke-detector http://www.theverge.com/2013/10/8/4790896/nest-protect-smoke...