Without subsidies and incentives, such as those in California, PV power costs about twice as much as utility power, says Thomas Leyden, vice president of east coast operations for PowerLight, a PV systems integrator in Berkeley, CA. That difference, however, is shrinking. “PV hardware prices have gone down tenfold in the last 15 years, thanks to new technologies, better manufacturing techniques, and more efficient use of materials,” Leyden says. Prices are currently falling by about 5.5 percent yearly, he says, so they should come down another 50 percent in a little more than a decade – and become fully competitive with utility power.
Maycock is even more optimistic, projecting that the installed price will fall from today’s $8 or so per watt to $4 by 2014. That would make solar power “fully economic in the Sunbelt,” he notes.
Meanwhile, Guha maintains that PV roofing is already economical at certain times of the day, in places where utilities charge extra for peak daytime usage. There, he says, it can be used to avoid paying those surcharges, a practice called “peak shaving.”
Historically, the biggest market for residential PV roofing has been in Japan, which gets about half the sunlight that California does and the average residential user derives only a kilowatt. But government incentives, low mortgage interest rates, and high utility power rates have made residential PV popular there, says Maycock.