How to size a biomass boiler and estimate fuel consumption

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.

As a rule of thumb for sizing biomass boilers:

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

James Eades

By: James Eades

Operations Director, James Eades is EnergyMyWay's in-house expert on renewable energy policy, microgeneration technologies and best practice in the renewable energy industry.