This paper describes the second step toward development of an affordable net zero energy house as part of the Department of Energy’s Building Technology Program. Building affordable houses that generate as much energy as they use is the long-term goal of that program. The house discussed in this paper is located in Lenoir City, Tennessee. A Habitat for Humanity family of three took occupancy in December 2003. This all-electric house has airtight structural insulated panels (SIPS), high-efficiency windows with a 0.34 U-factor and 0.33 solar heat gain coefficient, a SEER 14 heat pump, a space-integrated heat pump water heater, and a 1.98 kWp grid-connected solar photovoltaic system. Together these features, which cost less than $100,000 to construct, have led to an annual total energy cost of $0.88 per day after utility solar credits. Thirtytwo sensors were installed in the house to monitor thermal comfort, energy-efficient technologies, and the rooftop photovoltaic system every 15 minutes for longer than a year. Twenty three percent of the total energy demand of the house is satisfied by the solar photovoltaic system.

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