A periodic cleaning with a wire brush can increase heater efficiency. Heat transfer can be reduced by as much as 50 percent if there is 1/10 inch of soot, according to the U.S. Department of Energy's Energy Savers website.
Wood should be properly seasoned to maximize heat. It should not have any green and should have a moisture content of about 20 to 25 percent by weight. Wet wood uses a lot of energy, but if the wood is too dry, it will smoke and cause creosote.
The wood heater should be the right size to heat the space. A heater too large can release too much heat, which may require a reduction in the air supply entering the stove and reduce the stove's efficiency.
A blower can be placed in front of a stove to help distribute warm air. Additionally, a heat reclaimer can be installed to capture heat that usually goes up the chimney.