Of all the things K.K. DuVivier could hang on her refrigerator, that little piece of paper from Xcel Energy may tell her story best. It’s the energy bill that the Sturm College of Law professor and her husband, Lance Wright, are so proud of.

For a mere $5.91 a month, the couple powers their 2,200-square-foot home on South Gilpin Street. (The average electric bill in Denver is $78.01 a month, according to the non-profit Energy Resource Center.)

“We call ourselves the ‘Power Couple,’” DuVivier says with a laugh while setting out compostable plates and bowls. She is hosting a farewell for the house she designed and built 10 years ago — a labor of love she is leaving to be closer to her grandkids.

“I guess it’s good because I can pass this one on and move on to another house,” she says. “We very strongly wanted to get the word out and use this house as sort of a showcase to let people know [they can build a sustainable home too].”

Calling the three-bedroom, three-bathroom house sustainable would be selling it short. Modeled after an über-efficient German concept known as the passive house, DuVivier designed one of the country’s most efficient homes — a structure that actually generates more energy than it consumes. A well-insulated and well-sealed building means there is no need for gas or air conditioning.