moneyCleantech has been the industry of big-money investments in ambitious projects, but that may be changing, judging from a venture capital panel at VentureBeat’s GreenBeat conference today.

The most emphatic speaker on this point was Navin Chaddha, a partner at the Mayfield Fund. Chaddha said he’s more interested in investing “downstream” from energy generation, rather than in generation itself. That’s where entrepreneurs will find more opportunities, and those companies require less funding. As positive examples, Chaddha pointed to SolarCity (one of his portfolio companies) and SunRun, which aren’t trying to build giant solar plants or factories, and are instead trying to change the solar distribution model by bringing it directly to consumers.

On the flip side, he pointed to solar panel maker Solyndra, which has reportedly raised more than $1 billion but just announced that it’s closing one of its factories. $1 billion is more than most individual venture funds, Chaddha noted, and spending that much money on a single company is the “antithesis” of what venture capital is about.

Paul Holland from Foundation Capital added that cleantech investors are starting to feel pressure from their current portfolio companies. Firms that have invested steadily in cleantech over the past few years are finding that 40 of their companies need to raise more money, and that 20 of them need that funding in a matter of weeks or months.

“That’s a hard way to live,” Holland said.

Despite his emphasis on capital efficiency, Chaddha isn’t saying that he’s looking for unambitious companies that can sell quickly. In fact, he concluded that investors and entrepreneurs need to understand that cleantech companies take a long time to pay off.

“Let’s not live on the era of ‘97 and ‘99, and keep on waiting for things to happen in two years,” Chaddha said. “This is a marathon. This is not a sprint.”