Some of the biggest benefits came from choices that did not cost money per se, like having the front of the house face south to take maximum advantage of the sun. But other choices, like installing superinsulated windows and solar electric roof panels, added 8 percent to the cost, Mr. Doub said.  It did not take long for the gamble to begin paying off. In its first year, Solar Harvest fed enough energy into the local power grid during sunny spells to offset the cost of all the power it used other times. A copy of the $8.45 check that Xcel Energy, the utility, sent to settle 2006 accounts sits framed on the dining room table.  Mr. Doub especially enjoyed the tour he offered to 15 local land-use officials one day in early February 2007, when the temperature outside read just about zero. As usual, the indoor temperatures ranged in the high 60s despite the lack of any heat source other than the water tank and air circulating from the tightly insulated sun porch.  Even better, the home began attracting clients like Ronald M. Abramson, the president and chief executive of NexGen Energy Partners, an investment group focused on renewable energy projects, which Mr. Abramson recently moved from Maryland to Boulder. He worked with Mr. Doub for six months to develop plans for a 7,000-square-foot home for him and his family on a stretch of prairie near Lyons, not far from Boulder.  “We wanted to build the most environmentally responsible home in the country,” Mr. Abramson said.  Mr. Doub’s design for the Abramsons includes a combination of wind and solar power that is expected to generate 80 percent more energy than the house will require when it is finished early next year. And, with strict attention to the materials used and their environmental impact, the Abramsons think they can balance their carbon dioxide emissions and reductions.  Carbon neutral or not, the Abramson home is the first to meet new Boulder County regulations that set a sliding scale of permitted energy use, based on size. At the top of the scale, all new homes of more than 5,000 square feet must be energy neutral, generating as much as they use. County officials credit Solar Harvest with drawing support for the new regulations.  “We needed to be able to see some homes that were close to net-zero energy in Boulder County,” said Will Toor, a county commissioner. “Eric’s was the first, and that helped convince people it was feasible at a modest additional cost.”  Mr. Doub said that the smaller the home, the more challenging it can be to achieve a zero energy design because of the higher ratio of walls to interior space. Thus, Mr. Doub said, his work is in some respects less impressive than the single-story 1,130 square foot zero-energy home Habitat for Humanity built in 2005 in nearby Wheat Ridge with help from the National Renewable Energy Laboratory.  The several new Ecofutures projects begun since Solar Harvest was completed have come in at 7 percent to 9 percent above standard building costs, Mr. Doub said. He said that he continued to tinker with Solar Harvest, which cost $987,000 to build. During the unusually cold winter of 2006-7, the solar heating system proved inadequate, so he installed backup electrical heating. He also installed air-conditioning after finding that the only way to do without it in the summer was to wake people on the south side of the house at 5:30 a.m. to close windows before the sun came up.  Last fall, the family replaced its gas appliances with electric ones, partly to make Solar Harvest more representative of homes in the future. He said he expected natural gas prices to continue to rise, driving consumers to electric appliances.  A version of this article appears in print on , on Page SPG6 of the National edition with the headline: The Showhouse That Sustainability Built. Order Reprints| Today's Paper|Subscribe
The green home builder Eric Doub built a house that produces more energy than it uses. Now others are following suit, and that’s been good for business, he says.