When considering a biomass boiler or any space heating it is important to make sure the boiler is the right size for the property. Traditionally boilers have tended to be over sized which means that they only work at their peak efficiency for a very small amount of time.
You will need to know the area of the property the boiler is intended to heat in cubic meters then divide this by 30 to get the size of boiler in Kw
e.g. 420 m3 / 30 = 14kw boiler
If the property is well insulated you can divide the volume of the heated envelope of the property by 50 rather than 30.
To estimate the amount of fuel a biomass boiler will require per annum divide the boiler size by 4
e.g. 14 / 4 = 3.5 tonnes of fuel per year
At current prices 1 tonne of fuel costs approximately £250