The power depends on the size of the room that needs to be heaten, on the quality of insulation and on the climatic area
where the habitation is located:

- For a non isolated house located in a cold climatic area, you need about 70W/m³ 
- For a reasonably isolated house located in an average climatic area, you need about 50W/m³
- For a very good isolated house located in a hot climatic area, you need about 30W/m³

Example for a 85 m² habitation, with a 2.5 m ceiling high reasonably isolated and located in an average climatic area :

85 m² x 2.5 m x 50 W/m³ = 10625 W = 10.625 kW