Struggling with your wood pellet boiler running costs?

Struggling with your wood pellet boiler running costs?

02 August 2017

Are you finding your wood pellet boiler is burning more pellets and costing more to run than you expected? If you are then please read on.

One of the key areas to focus on is how well the wood pellets are burning inside the boiler.

Signs of poor combustion
  • Pellets burning out fast
  • Partly burnt pellets in the ash
  • Blackened but still complete pellets in the ash
  • Excessive amounts of either:
    • Ash output
    • Clinker on the grate or in the combustion chamber
    • Build up of soot and tar in the flue

The issue can often be related to the boiler itself and it’s worth making all the obvious checks (such as ensuring the combustion chamber is clean, seals around the door are sound, air holes are clear, pellets feeding in at the correct rate etc). Having your the boiler properly serviced once a year is ‘good practice’ to ensure it runs efficiently and the summer is an ideal time to do this.

If you have done all that and you haven’t seen a reduction in your running costs then it’s worth looking in detail at the pellets you are using.

Key things we see going wrong are:
  • Slightly damp pellets (normally obvious if the pellets are starting to swell up)
  • Excessive dust in the pellets
  • Fines (small particles of broken pellets)
  • Low calorific value (CV) of pellets

All of the above are normally as a result of poor pellet manufacturing, handling or storage.  They will all lead to excessive pellet consumption as the boiler typically tries to compensate for the pellet deficiencies by increasing the burn rate.

Excessive dust and fines leads to clinker and often temperature “hot spots” on the grate.  Damp pellets tend to fall apart and reduce the heat levels in the combustion chamber as the water content is driven off. Damp pellets can also jam the pellet feed, slowing down or stopping the intake of pellets.  Low CV pellets are normally a result of poor feedstock going into the pellets in the first place.

When pellets are made they need to meet a certain density to ensure that they actually stick together for the duration of the journey from the factory to your boiler.

It is no coincidence that the further they travel and the more they are handled, the more they are liable to fall apart and the higher the dust and fines content tends to be.

Fundamentally;  low quality wood pellets aren’t capable of producing the amount of heat expected. These have a high level of waste in terms of dust and fines which also  increase the wear, tear and maintenance on mechanical parts of your system. The increased running costs of your pellet boiler are due to using a higher volume of pellets for the heat output needed.


It can be difficult to know what is a high quality pellet and what isn’t. You can see the amount of fines, dust or swollen pellets in the bags or hopper.  But you can’t see the CV which is why we publish our monthly quality reports. These allow you to see our consistent quality month on month. Providing you with the information to compare our wood pellets with our competitors. Please take a look at our June report here June 2017 Woodlets – Certificate of analysis