U.S. Department of Energy - Energy Efficiency and Renewable EnergySolar Energy Technologies ProgramGrid-Connected PV Case Study: PV Power for an Energy-Efficient Home in Massachusetts
This grid-connected, PV-powered home in Massachusetts has been operating without a hitch since 1980. The owners of this house and its 4.5-kilowatt PV array sell enough excess electricity back to the utility in summer to nearly balance out the cost of the backup energy they buy from the utility in winter. Concerned about the environment and rising energy costs, a retired couple in Massachusetts commissioned the design of a PV-powered, energy-efficient, all-solar home. Although they wanted to be more self-reliant, they didn't want to maintain a battery bank at their home. Because utility power was available, they specified a utility-connected PV system. The privately financed home incorporates many energy-conserving features. Built largely of masonry, concrete, and steel with earth berms against the north, east, and west sides, it stays warm in winter and cool in summer. The south wall of the house is nearly all glass to soak up the winter sun, and the roof overhang shades the south-facing glass in summer. The PV modules occupy 430 square feet (40 square meters) of the south-facing roof. The direct current (dc) electricity from the modules passes through an inverter, which converts it to utility-grade ac power. The PV system generates most of the electricity the couple needs, making the home nearly self-sufficient, energywise, over the course of the year. During summer, the PV system generates more electricity than the house uses and sends the excess out into the utility grid. In winter, the house uses more electricity than the PV system produces, and so it draws some power from the grid. For additional PV case studies, see: |