Mar. 6--PROVIDENCE -- Alteris Renewables, the largest installer of solar-energy systems in the Northeast, is planning to purchase several companies to expand its presence to the mid-Atlantic part of the country.

Heartwood Group, a Providence-based alternative-energy company, says it expects to put twice as many photovoltaic cells online this year as it did last year.

The economy may be in recession, but executives from both companies who spoke at a roundtable discussion Wednesday night are banking on growth in the renewable-energy industry now that a green-minded administration is in Washington.

The $787-billion stimulus package is evidence of President Obama's support for renewable energy. The American Recovery and Reinvestment Act of 2009 provides billions of dollars in funding for green projects, creates new tax credit programs, extends others and sets up a groundbreaking system of federal grants for developers.

Robert Chew, director of wind energy for Wilton, Conn.-based Alteris, and Fred Unger, president of Heartwood, told more than 90 people at the event sponsored by the newly created Rhode Island chapter of the Northeast Sustainable Energy Association that they expect the stimulus plan to push the industry over the hump during a slow economy in which much of the funding for green-energy projects has dried up.

"But the stimulus is just part of the story," Unger said.

Installations of solar and wind systems have been increasing by 30 percent to 40 percent annually over the last few years, according to Unger. That growth may slow because credit has dried up, but the costs of producing energy from renewable sources is projected to decrease steadily. When so-called "grid parity" is reached -- a time when production costs for green energy are equal to those for fossil fuels -- the industry will thrive, he said.

"We are quickly approaching grid parity," Unger said. "When that happens, this market will take off."

Julian Dash, director of the state Renewable Energy Fund, and Karina Lutz, deputy director of the nonprofit People's Power and Light, also took part in the discussion at the Wolcott Eco-Office.

The office was built by John Jacobson and showcases sustainable building techniques and green technology. The building on Wolcott Street supplies all the energy it uses through solar cells.

Jacobson, president of JTJ Investments, a green development company, told the audience that a small community of eco-businesses is forming near his building in the Valley neighborhood.