All stoves are rated by their heat output range in kilowatts (kW). This rating depends not only on the size of the firebox in the stove, but also on the venting systems (both in and out) and on the type of fuel your stove uses.

This can be controlled by vents allowing you to alter the flow of air into the stove, affecting how quickly (and how hot) the burn is.

Mostly this is used when lighting the stove and it also allows the stove to be left on a slow burn, giving off gentle heat all through the night.