Along with Hyundai and Honda, Toyota has been one of the biggest exponents of hydrogen as an alternative to petrol and diesel power. As well as releasing the Mirai hydrogen fuel cell car, it has invested in fueling stations and infrastructure to make sure fuel cell vehicles aren't an under-supported flash in the pan, experience that will pay off when sales of its 77-seater Fuel Cell Bus start early next year.
The fuel cell in Toyota's bus draws from 10 high-pressure tanks, capable of holding a combined 600 liters (132 gal) of hydrogen at around 700 bar. Power comes from two electric motors making a combined 226 kW (303 hp) of power and 670 Nm (494 lb.ft) of torque.
As well as powering the bus itself, the fuel cell in the bus is able to act as a generator in emergencies. With a capacity of 235 kWh and a maximum output of 9 kW, Toyota says it could be used to power stadiums or homes in a blackout. It's an idea Nissan has been playing with in the UK, although its electric cars don't have quite the same capacity as the full-size bus.
Toyota has been testing its hydrogen-powered bus since 2015 in Japan, with other companies having been running trials in Hamburg and north-eastern China since 2009. The Fuel Cell Bus is expected to go on sale early in 2017, and there are plans to introduce 100 to the roads around Tokyo in the lead up to the 2020 Olympic and Paralympic Games.
Source: Toyota
https://www.solarisbus.com/vehicles_group/urbino-electric
So, whhy not run cars directly on nat gas instead, and avoid conversion loss?