Logs produce approximately 4.1kWh of energy per kilogram.  This  depends on how dry the wood is and the type of wood you’re using. For a batch-burning boiler such as the Effecta Lambda, we recommend logs that are 500mm long and 12-15cm thick.


Make sure that you only use sustainable wood. You’ll be doing such a lot to reduce emissions, it makes sense to boost your eco input! Check the wood doesn’t have any coatings or preservatives and that it’s as dry as possible: wet wood will only reward you with excess tar and soot which can wreak havoc on your flue.

See if you can get your hands on a moisture meter as this will help you test how dry wood is. If you’re dealing with harder woods, you’ll need around two years to season it properly, whereas soft wood needs closer to one year. 

Sourcing wood

When planning your biomass boiler installation you should also make sure you plan your fuel supply. If you have your own supply of logs, you must ensure they have a moisture content of less from 20% and should be seasoned for 1-2 years. A moisture meter will help you test how dry your wood is.

If you aren’t lucky enough to have your own supply, we recommend using the Biomass Suppliers List (BSL) for quickly and efficiently sourcing local wood, from suppliers you can trust.

This table gives you an idea of how wood compares to other types of fuel:

Fuel kg/m3 g CO2/kWh kWh/ Kg
Logs 350 7 4.1
Wood Chips 250 7 3.5
Wood Pellets 650 15 4.8
Coal n/a 484 8.6
LPG n/a 323 6.6
Heating Oil n/a 350 10
Electricity n/a 530 n/a
Source, Biomass Energy Centre