Ygrene Energy Fund has been sued in a potential class-action complaint that alleges the Santa Rosa company deceived customers about the costs and difficulties linked to its financing for home energy improvement projects.

The federal lawsuit alleges the company misled clients in California and Florida by suggesting they wouldn’t have to pay off their Ygrene financing if they sold or refinanced their homes. In reality, it is “impossible or nearly impossible for consumers to sell their homes without first paying off the loan and incurring a large prepayment penalty,” the lawsuit maintains.

The reason is that two key federally controlled mortgage enterprises, Fannie Mae and Freddie Mac, won’t purchase home mortgages on properties tied to financing like Ygrene provides, commonly called property assessed clean energy, or PACE financing. As a result, homeowners who want to sell or refinance their houses typically first must pay off their Ygrene financing, which often results in a prepayment penalty of 5 percent of the loan balance, the lawsuit alleges.

A Ygrene spokesman said the lawsuit lacks merit and vowed a vigorous defense.

“We hold ourselves to the highest ethical standards,” Mike Lemyre, a senior vice president, said in a statement. “Complete transparency and a commitment to consumer disclosure, protection, and education are of utmost importance to Ygrene.”

Lemyre declined further comment on the lawsuit’s specific allegations.

Ygrene, founded in 2010 by developer Dennis Hunter, calls itself “the nation’s leading provider” of PACE financing.

In December, the company announced it had received a total of $329 million in investments and had approved more than $1.85 billion in energy-efficiency projects for homes and businesses.

Ygrene and other PACE financing companies around the nation receive authorization from local governments to offer PACE loans in a particular jurisdiction.

Homeowners and businesses in those areas can borrow money for energy-saving projects and repay the loans via their property tax bills.

The idea was pioneered here by the Sonoma County Energy Independence Program, a government agency that offers financing for solar electric generation and other energy upgrades.

The suit alleges that Ygrene markets PACE loans through a network of 3,200 “ill-trained and self-interested” home improvement contractors who misrepresent the risks and restrictions of the loans to maximize their own profits.

The lawsuit was filed March 9 in the U.S. District Court in San Francisco by two firms that specialize in class-action cases: Kasdan LippSmith Weber Turner in Los Angeles and Tycko & Zavareei, in Washington, D.C. Attorneys did not return a call seeking comment.