Can home photovoltaic systems meet all the electrical needs of your house?
Probably not. The biggest limiting factor, aside from cost, is the area of roof available for the panels.
Solar panels capture only a small amount of the sun's energy each day -- about 15 percent. There are about four hours daily of peak energy capture in South Florida. Therefore, many panels are needed to run several appliances. Roof size as well as orientation limit the number of panels that can be used.
''If you look at a roof, it's generally large enough to support a photovoltaic system in the 4 to 6 kilowatt range,'' said Cocoa Beach solar expert Jim Dunlop. ``That will only produce 15 to 25 kilowatt hours a day. The average [home use] is upwards of 45 kilowatt hours a day. So size is limited to about half the customer's load.''
Bob Reedy, director of the photovoltaics division at the Florida Solar Energy Center, says a 1-kilowatt panel produces 4.5 kilowatt hours a day, so 10 panels are needed to meet the electricity needs of an average Florida home.
Dan Morris, who works with Vergona Bowersox Electric in Boca Raton, an electrical contracting firm with a photovoltaic division, said, ''The rough number we use is for every 1,000 watts (one kilowatt), you're looking at 100 square feet'' of roof space.
An energy-efficient home reduces the power needs.
Under new building codes, with energy-efficient lights and appliances in place, a home may well use less than half of the 45 kilowatt hours, Reedy said. ''So a 4 to 5 kilowatt hour system is sufficient if you have an energy-efficient home,'' he said.
Will four, eight or 10 panels stay in place in a hurricane?
The experts say yes.
Typically, arrays of panels are mounted parallel to the roof, just a few inches above it. The panels are lightweight and don't add any extra load.
''From an engineering perspective, if it's on the same plane with the roof, you really have almost zero wind resistance,'' said Reedy.
To be on the safe side, rooftop mounting systems for the panels are beefed up in Florida, the solar people say.
Reedy downplays the danger of flying debris. ''Anything can happen, but you just don't have problems with modern flush-mounted systems,'' he said.
The systems are tested for resistance to debris, said Sarah Howell in the Washington, D.C., office of BP Solar, which sells PV systems through Home Depot in some states (not Florida).
''We shoot hail at them at 90 or 100 miles an hour,'' she said. ``They also go through cycling of high and low temperatures.''