Venture capitalists are increasingly looking at the alternative energy market. In the last six months activity is way up; over the summer four solar-energy companies attracted $60 million in new financing, a showing impressive enough to spark the first talk of a "bubble."

Warren Weiss, general partner at Foundation Capital, says that alternative energy is

a very nascent market. It almost reminds you of looking at the Internet market 10 years before Netscape. You couldn't do it 10 years ago. We think the market is ready.

According to a recent survey, venture investments in alternative-energy companies jumped this year, although they remain a small slice of the overall business. Venture capitalists put $139.5 million into solar, wind and geothermal energy companies through the second quarter of the year, already surpassing the $95 million they spent in all of 2004, according to the National Venture Capital Association, Thomson Financial and PricewaterhouseCoopers.