October 09, 2007
| by Steven Castle
I attended a couple of green open houses last Saturday, Oct. 6, as part of the National Solar Tour put on by the American Solar Energy Society and its regional chapters. First stop was a Colonial-style house with a south-facing solar roof.
Homeowner Bob Zak of Bolton, Mass., showed off his photovoltaic system, which consists of 480 separate solar cells arrayed to the look like roof shingles. The entire roof, except for the half-shingles at the ends, was done with the Sunslates roofing system from Atlantis Solar Energy. You can see photos of Zak’s house on this site.
The Sunslates, in effect, take the place of traditional roof shingles and give the roof a uniform, unobtrusive look. Zak explained that he didn’t want traditional solar panels mounted on his roof, which faces the road. “I wanted something efficient, and that my neighbors wouldn’t mind.” The slates aren’t made with thin-film solar technologies, but of the more traditional crystalline silicon variety.
The Sunslates overlap, like roofing shingles, with each tile wired separately—although there is usually only one penetration point. The 20 arrays of 24 tiles each are wired to three inverters in Zak’s attic. The inverters convert the direct current (DC) generated by the solar panels to alternating current (AC) used for home’s electricity.
The 6-kilowatt system is tied to the grid, meaning that Zak effectively “sells” his excess power back to the power company. He went the grid route, he says, because “I didn’t want a roomful of batteries in the basement.” Batteries are often required to store electricity collected by a solar array.
Zak estimates that about two-thirds of his solar power makes it back to the grid, saving him about half a normal electric bill, or about $1,000 a year. He says the system cost him about $60,000 to have installed in 2001. He received a one-time state tax break of about $1,500.
According to Atlantis Energy, the roofing and electrical contractors who install its systems will on average charge $13,000 per 100 square feet—and expect about 1 kilowatt per 100 square feet and costs of about $13 per watt.
Although he’s in the northeast and gets plenty of snow, Zak says the snow melts quickly off the solar panels. Performance, water runoff, and installation costs also depend on the slope of the roof.
I’ll be writing about more green homes I’ve visited in upcoming entries. Let us know if you saw any as well!
Steven Castle is Electronic House's managing editor. he has been writing about consumer electronics, homes and energy efficiency topics for two decades. He is also the co-founder of GreenTech Advocates