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CORVALLIS, Ore. - With fluctuating prices of natural gas, fuel oil and electricity, many people consider heating their homes by burning firewood or wood pellets as a less-costly alternative.

When considering a change in home-heating energy use, it's a good idea to compare heat content of traditional fuels with wood and wood pellets. The most common measure in the United States is the BTU, or British Thermal Unit. One BTU is the energy needed to raise the temperature of one pound of water by one degree Fahrenheit.

A new Oregon State University publication compares several types of fuels based on their cost per million BTUs of available heat at a given price. The publication, "Home Heating Fuels," (EC 1628-E) is available online at: http://extension.oregonstate.edu/catalog/pdf/EC/EC1628-E.pdf

A table reveals that burning wood or wood pellets can be less expensive at a cost per million BTUs than natural gas, electricity, heating oil or propane. The publication also explains how to calculate the payback period for money spent on a new wood stove or insert.

Cost is not the only consideration, however, when deciding to switch to firewood or wood pellets.

"Firewood heating values vary significantly, depending on how dry the wood is," said Jim Reeb, an OSU Extension forestry and natural resources faculty member in Lincoln County.

Because the most important factor affecting BTU is moisture content, if you decide to heat with wood, you need to stack and season the wood through a dry summer and protect it from getting wet throughout the rainy season. Seasoning over two summers is even better, Reeb said. "Stacked wood should allow free air flow through the openings to facilitate drying."

Tree species also are important in heating value, Reeb pointed out.

"Denser hardwoods such as white oak have more wood and weight with fewer air spaces than lower-density trees such as red alder or true fir," Reeb said. Denser hardwoods provide longer-burning fires and greater total heating value per unit of volume. Softwoods burn more quickly and heat less efficiently.

Good quality wood pellets typically have low moisture content and are cost competitive with firewood. Pellets must be stored in a dry environment, and electricity is needed to operate the stoker. Unless you have a back-up battery system, you'll be without heat if the electricity goes off.

There also may be safety issues to consider. Wood smoke consists of a complex mixture of gases and fine particles. The particles are the problem and can get into the eyes and respiratory system. Modern wood and pellet stoves produce less particulate matter than either open fireplaces or older models of wood stoves, Reeb said. Highly efficient pellet stoves emit even less than wood stoves.

"When purchasing a new stove, look for a U.S. EPA emissions testing certification label," Reeb said. More information is in the OSU publication.