The size of a wood burning stove is directly proportional to its heating capacity. Stoves featuring a firebox volume of less than 2 cubic feet provide enough heating capacity for a single large room or a small cabin, whereas larger stoves are suitable for houses with open floor plans.
In addition to the size, other factors that affect the efficiency of a wood burning stove include the type of wood that’s used for fuel and the house plan. Manufacturers typically list a wide range that delineates the space a wood burning stove can properly heat. A range between 1,000 and 2,000 square feet indicates that the heating power varies greatly, particularly in relation to climate conditions. The downside of this rating is that it normally doesn’t consider the cases where a house is poorly insulated against heat loss. Furthermore, it ignores the heat production per firebox of different types of wood, such as maple, which produces more heat than spruce.
The maximum heat output is expressed in British thermal units. As of 2015, most popular wood burning stoves feature a range between 25,000 and 80,000 BTUs. Since using the maximum heat output of a stove for a long period of time can severely damage it, this rating tends to be misleading. Due to the lack of standardization when it comes to determining the maximum heat output rating, it’s not a reliable way to compare the efficiency of different stoves.