Specifications

How do I Estimate Annual Wood Consumption?
Where a dwelling has a Building Energy Rating (BER), for example when built, sold or rented, the
accompanying advisory report can provide some useful information on estimated energy consumption for
heating and hot water, as can existing oil or gas bills if there has been an old boiler in place previously. If the
information is available this is exactly what you need to calculate projected wood consumption.
Example 1: Calculating wood consumption from an existing oil bill – (using wood pellets)
Oil bill - shows that you use 2,000 litres of oil per year
Energy content of oil = 10.55 kWh/litre, therefore total “oil” energy used = 10.55 x 2,000 = 21,100 kWh
per year
Oil boiler eciency = 80%, therefore actual dwelling heat requirement = 21,100 x 0.8 = 16,880 kWh
New wood boiler eciency = 90%, therefore “wood” energy required to heat dwelling= 16,880 / 0.9 =
18,756 kWh
Energy content of wood pellets = 4.8 kWh/kg, therefore 18,756 kWh of energy required would mean
18,756 / 4.8 = 3,908 kg/yr = 3.908 tonnes of wood pellets per year.
Suppliers and installers should also be able to advise you on projected annual fuel consumption of the boiler.
If you know the installed or planned capacity of the boiler in kW, multiplying this gure by the number of
running hours per year will give you the number of kWh of fuel required.
This can then be converted, in a similar fashion to example 1 above, into the number of tonnes required, and
based on the energy content of the fuel being used.
Clockwise from top left: Wood logs –
stacked and covered; Fabric wood pellet
store; Outdoor wood pellet storage
(plastic example); Outdoor wood pellet
storage (metal example).