ALBANY, N.Y. (AP) -- As outdoor wood furnaces catch on with homeowners looking to escape high heating bills, they're running afoul with more town and village officials worried about smoked-out neighbors.

The units, also called outdoor wood boilers, are becoming a common sight along rural roads. They look like sheds or outhouses with chimneys on top, but actually circulate water into homes for heating systems or hot water.

Owners love them because they can avoid buying heating oil, though local officials worried about downwind neighbors have been restricting their use.

"Right now, we feel they're too inefficient and they're impacting everybody," said East Fishkill Town Supervisor John Hickman.

The Hudson Valley town late last month adopted regulations on outdoor furnace operations just as two Adirondack villages passed similar local laws; Tupper Lake banned new outdoor furnaces and Saranac Lake set its own usage regulations.

The municipalities joined about 50 other towns, cities, villages and counties across New York state that either regulate or ban outdoor furnaces. Many more localities in northern states have taken similar actions as outdoor furnace sales boom.

An estimated 14,500 outdoor boilers were sold in New York from 1999 to 2007 and 188,500 were sold nationwide, with the bulk of the sales in recent years, according to the New York Attorney General Andrew Cuomo's office. Ken Decker of Decker Heating & Construction said he has sold more than 200 this year from his store just west of the Adirondack Park — more than double his 2007 sales.

Prices vary depending on the manufacturer, but installed costs of $7,000 to $10,000 are common. The cost of firewood varies widely by region, though users who cut their own can recoup their investment in a matter of years. Consider that the U.S. Energy Information Administration predicts the average heating oil bill in the Northeast this winter will be about $2,600.

Jon Wilder, of Blue Arrow Farm southeast of Albany, said he and his family can collect enough wood for a winter over a few weekends in the fall.

"I get done with my three weeks of work and I look out my window and say, 'There's my winter heat,'" said Wilder, who also sells the outdoor boilers.

Decker and Wilder both stressed that smoke is not an issue as long as the boiler is stoked with dry, seasoned wood. They said problems occur when people burn cardboard or other trash. Decker said the outdoor units are cleaner than fireplaces.

"People see these ... with this plume of smoke coming off," he said, "so they point their fingers."

Regardless, drifting smoke is becoming an issue as the outdoor units multiply. Paul J. Miller, deputy director of Northeast States for Coordinated Air Use Management, said the problem is becoming more acute as their popularity spreads from very rural areas to villages and other densely populated regions.

Miller said the outdoor boilers can put out a thousand more times fine particulate matter per hour than gas- or oil-fired furnaces. The smoke can be especially hazardous to people with asthma and other respiratory conditions, he said.

The U.S. Environmental Protection Agency has a voluntary program that encourages manufacturers to sell cleaner-burning units, but there are no mandatory federal standards. Three New England states regulate outdoor boilers: Maine, Vermont and New Hampshire.