AT&T is now Silicon Valley fuel cell maker Bloom Energy’s largest customer that’s not a utility, according to San Jose Mercury reporter Dana Hull. Hull reports that AT&T more than doubled the size of its deal to buy power from Bloom Energy fuel cells to 17.1 MW. Bloom makes fuel cells that take fuel (natural gas or biogas) and combine it with oxygen and other chemicals to create an electrochemical reaction that produces electricity. Bloom Energy servers can deliver distributed power on site at a building, and this can have a lower carbon footprint and potentially more electrical reliability than grid power.