Recommended dimensioning of the boiler output power for wood gasification boilers:

For wood boilers, a decisive factor is how often the customer is able or willing to refuel the boiler. Therefore, the boiler output is not based on the heating demand of the building, but on the daily heating requirement.

Since the wood boiler must be filled manually, it requires the presence of the operator for heating up or refueling. During combustion, the wood gasification boiler can now supply the heating system as well as the buffer storage tank. The combustion time depends on the boiler output, the amount of wood logs filled in and the quality of the firewood. If a wood gasification boiler is sized exactly according to the heating demand, the operator would have to refill firewood immediately after combustion to avoid a heat deficiency and to prevent the building from cooling down too much. This is understandably not very useful. Therefore, a wood gasification boiler should be dimensioned, such that even on the coldest day, 2-3 boiler fillings are sufficient. For emergencies, an electric heater can be used as an additional heater in the buffer tank.

If you know your daily heat demand you can enter it manually (e.g. daily heat demand = heating load * 24 h).
The daily heat demand must be entered in kWh per day!

If you do not know your daily heat demand, you can calculate it approximately with our calculation program:

Approximate calculation of the daily heat demand based on heating and hot water demand

 kWh per day

 kWh per day


The approximate calculation of the daily heat demand is for information purposes only and does not replace the heating load calculation according to standard DIN EN 12831, which is required by law for new buildings.
The daily heat demand depends on the type of building (standard EFH 24 h), average room temperature 20°C, outdoor temperature on the coldest day of the year (default -16°C or depending on the location).
Firewood residual water content 15%, calorific value beech 4.2 kWh/kg, weight beech 460 kg/rm, calorific value spruce 4.3 kWh/kg, weight spruce 312 kg/rm.
This calculation of the necessary filling quantities is only intended to provide you with information and guidance. It does not replace professional planning and advice from the installer on site. The actual consumption quantities may differ from the example shown depending on user behaviour, wood quality and building data.