Wood-fuelled heating

Wood burning stove

Wood-fuelled heating systems, also called biomass systems, burn wood pellets, chips or logs to to provide warmth in a single room or to power central heating and hot water boilers.

A stove burns logs or pellets to heat a single room - and may be fitted with a back boiler to provide water heating as well.A boiler burns logs, pellets or chips, and is connected to a central heating and hot water system. A wood-fuelled boiler could save you up to £650 a year compared to old electric heating.

 

The benefits of wood-fuelled heating  

  • Affordable heating fuel: although the price of wood fuel varies considerably, it is often cheaper than other heating options.
  • Financial support: wood fuel boiler systems could benefit from the Renewable Heat Premium Payment and the Renewable Heat Incentive.
  • A low-carbon option: the carbon dioxide emitted when wood is burned is the same amount that was absorbed over the months and years that the plant was growing. The process is sustainable as long as new plants continue to grow in place of those used for fuel. There are some carbon emissions caused by the cultivation, manufacture and transportation of the fuel, but as long as the fuel is sourced locally, these are much lower than the emissions from fossil fuels.
 

Costs, savings and earnings  

 

Costs

An individual pellet stove will cost around £4,300 including installation. For boilers, an automatically fed pellet boiler for an average home costs between £14,000 and £19,000 including installation, flue, fuel store and VAT at 5%, and log boilers between £11,000 and £23,000. Pellet costs depend mainly on the size and method of delivery. Buying a few bags at a time makes them expensive. If you have room for a large fuel store that will accept several tonnes of pellets at a time, delivered in bulk by tanker, you can keep the cost down.Logs can be cheaper than pellets, but costs depend on the wood suppliers in your local area, as they cost a lot to transport. If you have room to store more than a year’s worth of logs you can save money by buying unseasoned logs and letting them season for a year. Search for wood fuel suppliers in your area at the Log Pile website.

 

Savings

Savings in carbon dioxide emissions are very significant - up to 14.5 tonnes a year when a wood-fuelled boiler replaces a solid (coal) fired system or electric storage heating. Financial savings are more variable - if you replace a older gas heating system with a wood-burning system you might save up to £80 a year, but if you are replacing an old electric heating system you could save as much as £650 per year.This table shows how much you could save by installing pellet central heating in a typical four-bedroom detached house with basic insulation:

Existing system

 

Savings per year

RHI income per year

Electricity (old electric storage heaters) £/year £340 to £650 £2,135 to £3,390
Carbon dioxide/year 8.4 to 14.5 tonnes
Oil older (non-condensing) £/year £335 to £470 £2,135 to £3,390
Carbon dioxide/year 4.8 to 7.5 tonnes
LPG older (non-condensing) £/year £950 to £1,435 £2,135 to £3,390
Carbon dioxide/year 4.7 to 7.3 tonnes
Coal £/year £265 to 425 £2,135 to £3,390
Carbon dioxide/year 9.0 to 14.5 tonnes
Gas older (non-condensing) £/year £25 to £80 £2,135 to £3,390
Carbon dioxide/year 4.0 to 6.3 tonnes

These savings assume the house has been insulated, as we always recommend that people insulate their homes properly before considering installing renewable energy systems. So you could save money from insulating, and then save the money from switching to wood heating too! We've assumed different boiler efficiencies for each fuel type; heat pumps produce more energy (as heat) than they use (as electricity), so their efficiency is more than 100%.  Find out more about how we made these calculations.

 

Earnings

You may be able to receive payments for the heat you produce from a wood boiler through the government’s Renewable Heat Incentive (RHI).From August 2011, you may be able to get help with the installation costs of a wood boiler through the Renewable Heat Premium Payment scheme.Pellet and log stoves are not eligible for Renewable Heat Premium Payments.

 

Green Deal finance and renewables

This technology is an eligible measure under the UK government’s Green Deal which is a financing mechanism that lets people pay for energy-efficiency improvements through savings on their energy bills.Further information on Green Deal.

 

  Maintenance

Wood fuelled boilers, stoves and room heaters should be kept clean and swept regularly to remove ash. Ash quantities are generally very low (<1% of fuel volume), but you will still need to empty the ash bin of a wood burning stove or boiler. This is likely to be weekly and never more than once a day. A log fire requires ash removal before every use.Some appliances particularly boilers have self-cleaning systems built in. A self-cleaning system will collect ash from the combustion grate and the heat exchanger tubes. If there is no automatic ash cleaning mechanism in place the boiler will need to be shut down periodically so that this can be done by hand. If the ash is not cleaned out regularly, it will build up and adversely affect combustion conditions, which can lead to boiler failure and shut down.

Some boilers have a mechanism for compressing the ash which reduces the number of times the ash bin needs to be emptied.With automatic ash removal and cleaning of the heat exchanger the only maintenance requirement will be occasional ash removal and an annual maintenance check (cost c£100).If you have a wood burning stove or boiler the chimney and flue pipe must be swept regularly to remove all soot deposits and prevent blockage. HETAS recommend that this “should be done at least twice a year, preferably before the heating season to check that the flue has not been blocked by bird's nests for example and also at the end of the heating season to prevent soot deposits from resting in the chimney during the dormant period”.

The Guild of Master Chimney Sweeps recommends that chimneys used in conjunction with wood fuel should be swept quarterly when in use.Further information on chimney safety can also be found in the National Association of Chimney Sweep’s leaflet Heat your Home Safely. Burning wet wood increases the amount of soot in a chimney and with it the chance of a chimney fire. Logs should always be seasoned (air-dried) for at least a year before being burned.

 

Choosing a wood-fuelled heating system  

  • Boiler or stove?
    Boilers can be used in place of a standard gas or oil boiler to heat radiators for a whole house, and to heat the hot water. Stoves are used to heat a single room, usually in conjunction with other heating systems, but may also have a back boiler to provide hot water.
  • Chips, pellets or logs?
    Chips are not suitable for heating a single house, but can be used to heat larger buildings or groups of houses. Pellets are much easier to use and much more controllable than logs; pellet boilers can run automatically in much the same way that gas or oil boilers operate. Log-burning stoves and boilers have to be filled with wood by hand; most pellet and chip burners use automatic fuel feeders which refill them at regular intervals. Logs require considerably more work, and you will need a lot of logs to heat a whole house, but they can be cheaper than pellets if you have a good local supply.
  • Do you have a local fuel supplier?
    Some companies now offer deliveries of pellets anywhere in mainland Britain and Northern Ireland; supply of logs is much more variable.
  • Do you have space?
    Wood boilers are larger than gas or oil equivalents. You will also need space to store the fuel: somewhere that's handy for deliveries but also appropriate for feeding the boiler.
  • Do you have somewhere to put the flue?
    You will need a flue which meets the regulations for wood-burning appliances: a new insulated stainless steel flue pipe or an existing chimney - though chimneys normally need lining to make them safe and legal.
  • Do you need permission?
    You may not need planning permission, but you should always check. All new wood heating systems have to comply with building regulations, and the best way to ensure this is to use an installer who is a member of a competent person scheme.
  • Do you have a thatched roof?
    Read HETAS's advice about building regulations (PDF, 741K).

Read our booklet A buyer's guide to wood-fuelled heating.

 

Before you start...

If you're thinking about installing a system to generate your own heat, make sure your home is as well insulated as it can be so your heat-producing system can be most efficient.

Focus on improving insulation and tackling draughts.