Toyota announced today that it will start selling buses that run on hydrogen fuel-cells in Tokyo next year in advance of the 2020 Summer Olympics. That news (first reported by Endgadget) in-and-of-itself isn’t that interesting — many cities across the globe have fleets of hydrogen-powered buses — but Toyota’s bus a nifty secret power: in an emergency situation, it can also operate as a high-powered external power generator.

“The Toyota Group considers the use of hydrogen to be a powerful source of energy for the future,” the company said in a statement, noting that its zero-emission Mirai fuel-cell sedan just went on sale.

Toyota’s fuel-cell buses will run on more powerful platform than the Mirai, with up to 10 fuel tanks holding 600 liters of highly pressurized H2 and producing 235 kwh, or almost three times the output of a Tesla Model S battery. This is what allows Toyota’s bus to double as an external power supply.

three times the output of a Tesla Model S

This bus isn’t the only vehicle that can be used as a power generator — GM’s Chevy Colorado ZH 2 is being used by the US Army to do just that — but Toyota says its bus’ fuel cells can generate enough power to light up a whole evacuation site, such as a school gymnasium.

The goal is to sell up to 100 buses in Tokyo before the start of the summer games. The Japanese government has committed to spending up to $6 billion to bolster Tokyo’s transportation infrastructure, including new roads and airport, rail, and port upgrades.