For solar energy to spread mainstream on U.S. homes, installation will need to move beyond specialized solar contractors to traditional building trades, such as roofers and electricians.

But traditional trades face varied challenges to add solar to their business, from training employees to finding new suppliers to even buying new insurance, participants said Wednesday at a Solar Idea Swap.

Some conventional companies have expanded into solar successfully, including Petersen-Dean Roofing and Solar Systems, a California firm that diversified from roofing, initially through acquisitions.

“There are learning curves in many areas:  technology, licensing. It’s a longer process than certainly I thought,” said Bill Scott, vice president of solar sales development for Petersen-Dean. “But if we’re really going to scale residential solar the way we want, it’s imperative that more companies do this.”

Deploying solar through traditional trades lets the solar industry tap a broad network of companies that already have trucks, workers and ample customer relationships, said Aaron Nitzkin, national sales director for Dow Solar, which sells roofing materials with photovoltaics inside.

The United States has nearly 93,000 contractors in heating, ventilation and air-conditioning and more than 63,000 in the roofing, siding and sheet metal field.  That compares with just 2,000 contractors specialized in solar. Most solar contractors tend to be small too. The top five — Solar City, Trinity, Real Goods, REC Solar and Verengo — share less than one-third of the U.S. solar home market, said Nitzkin.

“It’s easy to get into solar,” Nitzkin told some two dozen attendees. “It’s hard to scale.”

Traditional contractors stand to gain from solar by adding a new source of revenue, an option enticing in today’s weak economy. One heating and air-conditioning contractor in San Diego now does about four solar jobs a week. “They were able to leverage their relationships in sales,” said Paige Johnson, a solar business manager for Owens Corning of Ohio.

How quickly contractors expand into solar depends partly on the outlook for solar installations in their areas. California offers more opportunities than many places. “In Nevada, where I live,” said marketer Richard Small, “there are not a lot of incentives to make this an attractive business.”

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