When the Solar Energy Research Institute, now National Renewable Energy Laboratory in Golden, staged a tour of 12 new solar home designs built across the Denver area in 1981, engineer John Avenson bought a tour house that was built in Westminster.

The month-long Institute tour drew a hundred thousand visitors to homes scattered around Golden, Arvada, Denver, Aurora and Boulder, in a cold winter when energy savings were a hot topic nationally.

Fast-forward to today, and Avenson has refitted the house for a quantum leap in performance — so energy efficient that he charges his Chevy Volt car on excess power produced and still gets a $300 check back from Xcel every year for added electricity he supplies to his neighbors.

Avenson’s house in the Westbrook area off Wadsworth Boulevard at West 100th Avenue is one of a dozen homes that are open Saturday as part of the one-day Metro Denver Green Homes Tour.

For a $10 donation, participants can register for the self-guided tour at MetroDenverGreenHomesTour.org or pick up a map at the American Mountaineering Center, 710 10th St., Golden.

Following the Institute’s tradition, the event is carried out annually as a fundraiser for non-profit organizations New Energy Colorado and the American Solar Energy Society. The Society, Avenson said, was founded in 1954, around the moment when the Bell Telephone Laboratories invented the solar battery.

The Westminster house, built by Walden Homes, had no solar cells on it when the original tour opened — as they were still too expensive to incorporate. But costs have dropped radically, and Avenson, who spent his career with Bell Labs, added three kilowatts of photovoltaic cells in 2006, then took the system to the 14 kilowatts it generates today.

Meanwhile, he extensively modified the home’s original solar design for more efficiency — super-insulation, computerized shades to keep the passive solar from overheating in winter and replacing the original furnace with a heat pump matched to an energy-recovery ventilator. The backup heating-cooling system is now so efficient, Avenson said, he heats and cools the entire house on around 200 watts of power. A hairdryer uses around 1,300 watts.

Other solar homes are on view in Broomfield, Golden, Lakewood, and Superior.

In Arvada, one of NREL’s project managers has his newer, custom solar home on view. Owners of the 12 homes will be on hand during the tour to talk with visitors about their modifications and experiences.

Tour homes are open 9 a.m. to 4 p.m. The Mountaineering Center will have an energy expo in the parking lot, including a “tiny home” design on view until 7 p.m., and volunteers will offer rides in electric cars.