Forestry Commission Scotland logo
Log boiler

Log boilers

Modern log boilers can provide clean and efficient heating to all domestic-sized situations and for heating larger spaces such as village halls with a heat output need of up to 70-80 kW.

Larger boilers are available but require a considerable amount of stoking.

Important: before purchasing any equipment, read Managing a successful wood fuel installation and get expert advice.

Log boilers need to be stoked only once or twice each day. They operate at high levels of efficiency and have large combustion chambers. Some boiler models can take large logs up to a metre long, which reduces the work of sawing logs. Stoking should take no more than five to ten minutes each day.

Heat is produced in a log boiler relatively quickly and is used to heat water up to around 90 degrees C. The heated water is stored in a highly insulated tank called an accumulator tank. This can be used to deliver both central heating and domestic hot water to the house for the rest of the day, in a programmable way.

The accumulator tank can be integrated into a system with different heat sources. For example, the water could be pre-warmed by solar panels, or come from other wood burning stoves or a kitchen range, an electric immersion heater, or an oil fired boiler which could also provide a back-up heating system.

Due to the fact that they require manual stoking, log boilers may not be suitable for everyone, but for those who have the resources and time they can be an ideal low cost option, especially where potential end users have their own source of fuel.

Combination log boilers

Some manufacturers incorporate automatic feed pellet burners into their log boilers.  These combine the best features of a batch fed log burner and an automatic pellet burner, giving the user considerable flexibility over the way in which the boiler is operated, depending on the fuels available. A pellet fuel store or silo is needed for use with this type of boiler.


Some log boilers come with automatic de-ashing, in which case you will only need to empty the ash bins on a weekly/monthly basis, dependent upon moisture content of the fuel and level of use.

If you don't have auto de-ashing, excess ash needs to be removed from the boiler's loading chamber following each use. You should usually leave some ash in the combustion chamber to provide a burning bed for the logs.

Air openings in the combustion chamber should also be checked.

When cold, and on a monthly basis, a more detailed clean is usually required necessitating the removal of accessible combustion chamber parts.

The fan should be cleaned every three months.

Log boilers must be serviced by the manufacturer or installer annually.

HETAS are the official body recognised by Government to approve biomass and solid fuel domestic heating appliances, including the registration of competent installers.