The Viessmann  Vitovalor 300-P is a natural gas powered fuel cell boiler.

The fuel cell operates like  a battery, a chemical reaction takes place between the positive and negative electric poles. Hydrogen reacts with oxygen to produce electricity and heat, and water vapour. As there is no widespread infrastructure for supplying hydrogen, natural gas (CH4)is use to run stationary fuel cell devices.

Viessmann has integrated the fuel cell made by its Japanese partner Panasonic into  compact complete system and adapted it for use  in Europe. The fuel cell module with a gas condensing boiler to cover peak demands for heat, a hot water buffer cylinder (130 litres )

The Vitovalor 300-P has gained MCS certification entitling owners to claim under available feed in tariffs.

Energy efficiency category A++

Fuel cell module 
Electrical Output 750 Watt
Thermal Output 1kW

Gas Condensing peak load boiler
Thermal output 5.5 to 19 kW, optional up to 25.2 kW

The Princes Natural House was chosen to demonstrate this technology as it had two conventional gas boilers, one for each side of  the semi-detached house. Vitovalor unit lend itself to larger houses, and in this case both sides, comprising one 3 bed house, one studio unit and a two bedroom apartment above. This could also be appropriate for Houses of Multiple Occupations (HMOs) that have a high heat and hot water requirement with the electricity generated   to run the communal areas.

https://www.viessmann.co.uk/products/combined-heat-and-power/fuel-cell/vitovalor