The most important consideration when purchasing a stove is the required output to heat the room it will be placed within. As a very rough guide, measure the room and multiply width x depth x height (in metres), and then divide this by 14. This will provide the average heating requirements for the room in kilowatts. e.g. For a room measuring 4.9m x 4.9m x 2.4m, multiply these together and then divide by 14. This makes a 4.1kW output.