Dive Brief:

• A house built with solar panels, thick walls, triple-pane windows and plenty of insulation will generate energy bills that are 75% lower than an otherwise identical home built without those features.

• In a five-year study by TVA of three homes with matching floor plans, square footage and exposure to the sun found that a high performance, “zero-energy” home to a family of four would have an annual utility bill of about $400. The family in a typical spec home would pay $1,600 a year. And an energy-efficient home without the solar feature would rack up $1,000 a year in electric and gas bills.

• To remove the variation that would occur if different families with unique lifestyles lived in the study's homes, researchers equipped each one with robotic arms that simulated human activity—like opening the refrigerator door, running the dishwasher and turning lights and TVs on and off—so energy use would be identical in the three structures.

Dive Insight:

The high-performance home cost about $30,000 more to build than the “normal” house. Aside from ultra-tight sealing and solar panels, its major energy-savers were ductwork installed in conditioned spaces and a heat pump water heater.