Solid Fuel Boilers

Solid Fuel Boilers

You’ve got free (or cheap) firewood available? Why not use it to heat your entire house?

With a solid fuel boiler, you can!

A solid fuel boiler operates like a wood fireplace or stove, expect that instead of producing heat in the room, it heats water which is pumped into a hot water storage tank. The hot water in the tank is the used to heat your radiators just like a diesel- or gas-fired system.

The most common fuel types are wood or coal. Some boilers are designed to use a range of different fuel types, and the manufacturer will tell you.

The plant required is more substantial than gas or diesel boilers. In addition to the boiler, you’ll need a water storage tank. 1000L – 2000L is typical for a domestic installation.

You’ll also need a flue for the boiler. These are usually substantial and will generally be 6m-10m in length, and 100-150mm in diameter for an insulated flue. The manufacturer should tell you what sort of flue to install. If you’re pricing up a solid fuel boiler, make sure you allow for the flue cost as it will set you back a few thousand dollars.

All of the plant will need to be in a garage or dedicated plant room with a concrete floor, out of the weather. The boiler needs to be accessible for cleaning. There’s usually a cleaning port at the back as well as the front, and the flue will probably need to be accessible for sweeping too.

A solid fuel boiler differs from a diesel or gas boiler in that it can’t shut off its supply of fuel – once you put wood or coal in the fire box, it keeps on burning. This is why we need a water storage tank – to absorb the extra heat when the boiler is burning but no heating is required.

So if you don’t mind loading, stoking, and cleaning your boiler by hand, and if you’ve got access to an abundance of fuel, then a solid fuel boiler may be for you.


Cheap or even free fuel if you have firewood available
Doesn’t burn fossil fuels


Expensive to install
Space intensive
Has to be loaded and stoked manually