Wood-burning furnaces offer a potentially cheaper heating alternative, based on the fluctuation of gas and oil prices, reports eHow. However, the advantage of a multi-fuel furnace is the ability to alternate between wood, coal, oil or gas, as prices fluctuate due to market or seasonal demands, according to HomeAdvisor.
There are other efficient benefits of outdoor furnaces, such as a more even distribution of heat throughout the home. This is because the heat is carried through pipes, radiators or forced-air heat exchange, rather than being placed in a central room. Since the units have a higher capacity, they can burn much larger pieces of wood than a central indoor model. Additionally, the intensity of the heat is much greater so that wet and unseasoned wood still burn efficiently. Outdoor furnaces also have the ability to heat adjacent buildings, such as garages, sheds or outhouses. There's much less fire risk, since the fire itself is burned outside, away from the home.
One of the disadvantages is a high volume of smoke production. Some states and jurisdictions have regulations about smoke levels. Also, maintaining the operation of the furnace can be cumbersome. Cleaning ash periodically is required to keep the unit working efficiently. Loading wood twice a day is required in order to keep the unit heating efficiently, especially in colder winter months. Purchasing, transporting and storing wood is the responsibility of the customer, and space is required for storing an abundant wood supply.