How much heat do you need from your stove?
To produce a comfortable room temperature of around 21º/22º Celsius (70º Fahrenheit), when the outside temperature is 0º, you will need about 1kW of heat for every 14 cubic metres of space. 1kW is the equivalent of approximately 1 bar of an electric fire.
The following formula and example will give you a reasonable guide to the heat output you are likely to need. To establish the cubic capacity of the room, measure the length by the width by the height, for example a room that is in the region of 6.5 metres. (21ft. 6") x 4.5 metres. (15ft.) x 2.4 metres high (8ft.) will require a stove of about 5kW output to adequately heat its 70.2 cubic metres.
Please note that this calculator is designed to give you an estimate to the heat output needed to heat your room. The ability of a stove to heat your room is affected various elements including: the number of doors and windows in the room, other draft sources and the general insulation of the building.