PORTLAND, Maine — When oil prices skyrocketed to more than $4 a gallon four years ago, Dan Stevens got rid of his oil-burning furnace, oil tank and heating baseboards and began using wood to heat his home. He wasn’t the only one.

The number of households using wood as their primary heating source nearly doubled in Maine from 2000 to 2010, while growing by a third nationwide, according to U.S. Census figures.

Stevens never was a fan of heating oil — he doesn’t like the idea of oil coming from overseas, he had troubles maintaining his furnace and he wasn’t keen on the feel of oil-fired heat. When heating oil prices rose to over $4 a gallon in 2008, he finally turned to wood to heat the rambling three-story wood-frame house in Gardiner.

He now uses one wood stove that burns firewood and another that burns wood pellets in the home where he lives with his wife and their youngest son. When needed, he has two small propane heaters for supplemental heat.

Since the change, he estimates he has been spending $2,500 or so on cord wood, wood pellets and backup propane. That’s less than half what he was paying annually when using oil.

“Maine’s got trees, so you can buy local this way and still heat your house,” Stevens said. “And the heat is definitely cheaper.”

Oil is the No. 1 heating fuel in Maine and across much of the Northeast. Three out of four households in Maine use oil as their primary heating source — making it the most oil-dependent state for heat.

Residential heating oil last week was going for $3.97 a gallon on the East Coast — although it’s cheaper in Maine — up 58 cents a gallon from a year ago, according to the federal Energy Information Administration. Ten years ago this week, it was selling for $1.19 a gallon.

Oil consumption has fallen as homeowners have found other sources of fuel, with wood being the fastest-growing alternative, according to census figures.

About 2.1 percent of U.S. homes, or nearly 2.4 million households, used wood as their primary heating source in 2010, according to the U.S. Census Bureau. That was up from 1.6 percent in 2000, or under 1.8 million homes.

Among states, the number of homes using wood as a primary heat source went up 135 percent in Michigan and 122 percent in Connecticut, while nearly doubling in New Hampshire, Massachusetts, Maine, Rhode Island, Ohio and Nevada. The top wood-burning states per capita are Vermont, where 15 percent of homes use it as their primary heating source; Maine, 12 percent; Montana, 8 percent; and New Hampshire, 8 percent.

Wood is an often-overlooked source of heating fuel, said John Ackerly, president of the Alliance for Green Heat, a Maryland-based nonprofit that promotes the use of wood heat.

Wood was the primary heating source in 23 percent of U.S. homes in 1940, but had virtually disappeared by 1970, according to the Census Bureau. It has become more popular in recent years mainly because of the high price of oil, Ackerly said. People are also drawn to wood because it’s both a renewable and local product, and it’s free for people who live on wooded lots.

“It’s kind of under the radar,” Ackerly said. “It’s more a popular movement. It’s not driven by big investments and big projects that are covered by the media. It’s driven by individuals who don’t have much of a voice.”

New wood stove models, those made since 1990, have had to meet specified EPA emissions standards and shouldn’t even have smoke that is visible when used properly, Ackerly said. But he cautions that there are still concerns about pollution — and elevated risks for people with respiratory illnesses — from old models that people may be dusting off and from people who use green wood in the new models.

Pollution isn’t considered much of a public health issue in the East, he said, because the smoke easily disperses and stoves aren’t used a lot in urban areas. But out West, particularly in valleys with temperature inversions, wood stove smoke can create pollution problems, he said.

Meanwhile, firewood sales have been hot. Southern Maine Firewood, in Gorham, ran out of seasoned firewood for this winter in November. The company sold 3,200 cords last year, up from 2,300 in 2009, said officer manager Shellee Zaharis.

“Oil’s so expensive, and it seems that people are worried that the 2008 oil prices are going to come back,” Zaharis said.

Wood stove sales have been brisk at Rocky’s Stove Shoppe in Augusta, said owner Rocky Gaslin. Sales of both firewood- and pellet-burning stoves roughly doubled from 2010 to 2011, he said. A medium-size firewood-burning stove that can heat up to 2,000 square feet costs from $1,700 to $2,500, plus installation, while a similar-size pellet stove would sell in the $2,500-$4,000 range.

“People are trying to do as much as they can to replace oil,” he said. “They don’t want to burn a drop of oil at $3.50 a gallon.”

In the small town of Somerville, Dr. Roy Miller heats his 1,400-square-foot house with a wood stove and two propane heaters for backup. He usually spends $600 to $800 burning three to four cords of wood a year, plus another $600 to $700 for propane. Miller, a family doctor, likes being able to make his house toasty warm without feeling guilty or wasteful, the way he might if he were cranking up an oil furnace.

“If at the end of the year we use an extra half cord, that’s just $100,” he said. “You can do that in a couple of nights with oil.”