When the threat of wildfires has forced power to be cut in the tourist town of Calistoga, California, on the edge of Napa ...

But now Calistoga is shifting to a first-of-its-kind system that combines two clean-energy technologies — hydrogen fuel cells and batteries — for enough juice to power the city for about two days.

Lisa Gift, a resident who also serves on the city council, noted Calistoga is already grappling with climate change that is fueling more intense and frequent wildfires. “Continuing to depend on ...