The coal trend is consistent with steep increases in other forms of supplementary heating that people can use to save money  most of them less messy than coal. Home Depot reports that it has sold more than 80,000 tons of pellet fuel, a sort of compressed sawdust, for the season to date. That is an increase of 137 percent compared with the same period last year, said Jean Niemi, a company spokeswoman.

Image Problematic in some ways and difficult to handle, coal is nonetheless a cheap, plentiful, mined-in-America source of heat. Credit... Laura Pedrick for The New York Times

Coal may never make economic sense in areas far from where it is mined. But in places within reasonable delivery range, the price tends to be stable, compared with heating oil or natural gas. Prices for natural gas more than tripled in recent years before plunging in the last few months amid the downturn.

Coals vary in quality, but on average, a ton of coal contains about as much potential heat as 146 gallons of heating oil or 20,000 cubic feet of natural gas, according to the Energy Information Administration. A ton of anthracite, a particularly high grade of coal, can cost as little as $120 near mines in Pennsylvania. The equivalent amount of heating oil would cost roughly $380, based on the most recent prices in the state  and over $470 using prices from December 2007. An equivalent amount of natural gas would cost about $480 at current prices.

Mr. Buck said he could buy coal for $165 a ton. On a blustery afternoon recently, he was still studying the manual for his $2,300 Alaska Channing stoker, which gave off an intense heat in the den. An automated hopper in the back slowly dispensed fine anthracite coal chips into the stove’s belly, and every couple of days, Mr. Buck emptied the ash. He said he hoped the stove would cut his oil consumption in half.

“Now, somewhere, you’ve got to take into account the convenience of turning up your thermostat, versus having two tons of coal to shovel and the hopper and ashes to deal with,” Mr. Buck said. But if the $330 worth of coal in his makeshift bin “heats the house for the winter,” he added, “you can’t beat it.”

Wesley Ridlington, a homeowner in Fairbanks, Alaska, bought an outdoor coal furnace for $13,000 in March and uses it as his main source for heat and hot water.