Roofing contractor Bob Kulp says he started selling solar systems because he figured his company works on the roof anyway. At the time — 2009 — many in the roofing industry saw solar as a huge potential profit opportunity.

Kulp, owner of Kulp's of Stratford, in central Wisconsin, which does windows, siding, and decks, in addition to roofing, climbed the mountain of research and due diligence needed to find the right products and to train installers. It took five months to “get the right personnel in place,” he says.

The company sold its first solar job in August 2009 and today offers three photovoltaic solar products. Its solar division, Marathon Solar Roofing, has sold 40 systems, 80% of them residential. A pin map on the wall in Kulp's office shows the location of each.

THE SOLAR SURGE Solar — a technology available for decades and one that has waxed and waned — is in comeback mode. With improved product, a cost affordable to many homeowners, and incentives such as rebates, tax credits, and SRECs (solar renewable energy credits) making it more affordable still, residential solar systems began to take off in 2009.

There was a time when a solar system mounted on a roof was viewed as odd. But today the technology is more sophisticated and the appeal broader. “People are not questioning the technology,” says Tony Ruffine, vice president of sustainability and strategic markets for GAF Solar, a division of the roofing manufacturer. “They're questioning the financing, the payback, and the service. That's what needs to be sold.”

According to research company Greentech Media, residential and commercial solar installations in the U.S. have more than doubled in the last two years, to 213,957. What some saw as a fad now seems to have a solid future as a reliable energy source; one in which millions of Americans might be persuaded to invest. A study released May 1 by the Howard H. Baker Jr. Center for Public Policy, at the University of Tennessee, shows renewable energy following a path of steadily expanding use tied to incentives.

But the incentive picture is changing. Some state programs, such as Pennsylvania's Sunshine Solar Rebate, as well as some local tax credits, are depleted. According to The New York Times, clean energy funding from all sources fell from a peak of $44.3 billion in 2009 to $16 billion in 2012 and is projected to drop to $11 billion in 2014, an overall decline of 75%.

If you, an installing contractor, are trying to sell a solar system to a homeowner, incentives often make the difference. For example, one Saturday this spring a salesperson from American Century Solar, a division of American Design & Build, in Maryland, showed a Montgomery County homeowner a 6 kilowatt solar system. The county is one of five in the state offering a property tax credit of up to $5,000 for installing solar. Or was. That's now “down to four,” says American Design & Build vice president Kevin Carmen. That much money on a system selling for somewhere between $30,000 and $40,000 can be “a deal-breaker,” he says.

LOCATION, LOCATION, LOCATION The attraction of solar power is a local affair. To sell it, you must know what incentives are available and be able to process the applications. Kulp, for example, has one person in his office knowledgeable in that paperwork.

In the states with the highest electrical rates — California, Hawaii, New Jersey — solar has emerged as a strong alternative to conventional fossil fuel use. California, for instance, has enough solar-generating capacity to power 267,000 homes. On the other hand, Virginia — according to the Solar Energy Industry Association (SEIA) — has enough solar power for 560 homes.