Castle Drogo: Biomass boiler house

 Another example of renewable energy being used. The poster claims 690000kWh. I take it that means per year, although it does not specify. 690000/(365x24) = 90kW which sounds realistic if it were running all the time. But say electricity were 10p per kWh, it would represent £69,000 a year of heating.

The diagram suggests that the system is 94% efficient.