The size of the kW of the boiler is chosen by looking at the size of the house in m2, the age of the house and whether the house is detached, semi-detached, in a town or in the country. The age of the house. e.g. a house aged 20-30 years will often use about 1 kw per 10 m2 so e.g. 180 m2 house = 18 kw. Newer houses use less and older houses use more.
Solid fuel, stoker fuels (wood chip, wood pellet and corn) or both? If you only wish to burn solid fuel (timber only) then you do not require the stoker but the facility comes with all boilers that you can add a stoker at a later time.
If you mix your fuels ¬ it will burn all fuels safe for stoker use. If you burn timber in your boiler and you have already set up your stoker - the stoker will automatically stop feeding in fuel and burn the solid fuel first.
One of the most important things about the boiler is that you choose something that fits the needs of your home, has good efficiency and is easy to clean.