A few dozen companies say advances in technology will let them halve the price of solar-panel installations in as little as three years.

By 2014, solar-system prices will be competitive with conventional electricity when energy savings are figured in, Deutsche Bank says.

Venture-capital firms pumped $264 million into solar companies in 2006, up from $64 million in 2004, research firm Clean Edge says. The start-ups also have benefited from $159 million in U.S. research grants this year.

The solar industry is expected to triple in the next three years, from about $13 billion to $40 billion in revenue, says analyst Jesse Pichel of Piper Jaffray.

Like wind power, solar energy is spotty, working at full capacity an average 20% to 30% of the time. Solar’s big advantage is that it supplies the most electricity midday, when demand peaks. And it can be located at homes and businesses, reducing the need to build pollution-belching power plants and unsightly transmission lines. In states such as California, with high electricity prices and government incentives, solar is already a bargain for some customers. Wal-Mart recently said it’s putting solar panels on more than 20 of its stores in California and Hawaii. Google is blanketing its Mountain View, Calif., headquarters with 9,212 solar panels, enough to light 1,000 homes.