As winter approaches, homeowners across Maine have been preparing themselves for the change in temperature and the risk of the unmanageable cost of oil heat.

A wood stove at 60 percent efficiency with wood at $200 per cord can deliver 1 million Btu to a dwelling for $14.

Oil at $2.60 per gallon and with a heating system operating at 80 percent, efficiency will deliver heat to a dwelling at $25 for 1 million Btu.

I think wood is even more economical than this nearly 2-to-1 cost advantage would imply. The oil unit is in the basement with much duct work or piping between the heating unit and the living space. With the wood stove in the heated space, losses to the heat distribution system are eliminated. Stoves installed in the basement will do little to help heat the house – all one gets is early tulips.

Wood does have disadvantages: awkward storage and handling, clutter in the living area, odors of smoke during startup, deposits in the chimney, the constant need for attention and the concern for outside air pollution.

Once steady state is reached – a new stick put on the fire every hour or so – most stoves will operate in a relatively clean fashion. Endless data on thousands of stoves prove the best efficiency (least pollution) occurs when a large fraction of a particular fuel load is burned within an hour after loading. Filling the fire box, then closing the damper in hopes of a long burn is a recipe for inefficiency, pollution and creosote-related chimney fires.

I operate two Jotul No. 602 wood stoves. One is generations old, developed in Norway during World War II. The second is the same frame size, but redesigned to meet Environmental Protection Agency emissions requirements.

The old unit will hold seven split pieces of 18-inch firewood. Total fuel weight is 15.25 pounds.

The new unit – looks the same from the outside except for the glass in the door – holds only four sticks for a total weight of 10.5 pounds.

Some of the sticks must be less than 16 inches long. The old unit had a damper in the door that could shut down the air supply for a long burn. The new unit has a damper in the door, but other air passages within the stove are not assessable to the operator. One can’t shut this stove down for a long – and polluting – burn.

Wood stoves do not fit the modern lifestyle. One can’t build a fire in the morning, take off for school or work, and expect to come home to a warm house for lunch. But for a retired college professor, it is just the thing. He can fantasize about being Humphrey Bogart and that the stove is the African Queen.

Richard Hill is a retired professor of engineering at the University of Maine in Orono.