The omission of renewed investment tax credits for solar energy in the wide-sweeping energy bill signed by President Bush late last month has put the future health of the U.S. solar power industry in question.

The bill includes more stringent mandates for fuel economy and energy efficiency, but it doesn't extend the investment tax credit for companies specializing in solar power systems. That credit, which amounts to 30 percent of the value of qualified residential or commercial solar equipment, is set to revert to 10 percent at the end of 2008 unless it is extended.

Solar companies also lost out because the bill didn't include a mandate that would have required utilities to produce up to 15 percent of their electricity from renewable energy sources. More than half the states, most of them in the Northeast and on the West Coast, already have similar requirements.

A federal mandate could have bolstered the solar industry by encouraging utilities in regions such as the Southeast, where most states don't have renewable energy standards, to buy more energy generated by the sun.

Unless the investment tax credit is renewed before the end of the year, companies that produce solar power and related technologies in the U.S. are likely to scale back or scrap existing projects and seek more business overseas, analysts say.

"There is nothing favorable in this bill for the solar industry," said Michael Carboy, managing director and clean energy research analyst for Signal Hill Capital Group LLC, a Baltimore-based investment bank for small and midsize companies.