The United States is lagging behind in the $50-billion global market for clean energy, panelists said at the Red Herring spring conference.

While clean-energy investment has been growing in the U.S., panelists said American purchases have been lower than those in countries such as Germany and Japan. Unlike the U.S., those countries—and others—have widespread subsidy programs for renewable energy.

“One of my partners is in China this week,” said Bill Green, managing director of VantagePoint Venture Partners. “He called me and said, ‘The game is over and it’s not being played in the U.S.’”

The audience reacted with nods, smirks, and head-shaking, as people agreed, disagreed, and expressed surprise. The panel discussed the issue Thursday, the final day of the technology conference in Monterey, California.

The panelists agreed that the largest renewable-energy markets are not in the U.S., but disagreed somewhat about where and how far the U.S. has fallen behind.

“I wouldn’t go so far as saying the game is over and we lost, but there are certainly big drivers overseas,” said William Acker, CEO of MTI Micro Fuel Cells.

European wind projects have outpaced those in the U.S., said Chuck McDermott, a panelist and general partner with RockPort Capital Partners. The biggest solar companies, such as Sharp Electronics, Sanyo, and BP, are also based outside of the country, said Mr. Green. And Konarka, an American solar company, is one of several that have opened facilities in Europe in the last year.

“In energy, it’s far more interesting to look at technology outside of the U.S.,” said Mr. Green. “I don’t know where we have a leadership position.”

But Nancy Floyd, managing director at clean-energy investment firm Nth Power, said the U.S. does have some interesting technologies. The problem is not technology, but government policies, she said.

“One company we invested in is selling 100 percent of its goods to other countries,” she said. “We are losing jobs, losing our leadership position. We’ve certainly lost it in wind, where we were a leader in the 1980s. Because of our policies, we are going to see products sold there and manufactured there.”

After the panel, she added that Nth Power encourages its portfolio companies to sell outside of the country.

About 16 states currently have renewable-energy requirements, but there is no federal standard, said Mr. Green. He added that the different state policies make it difficult for clean-energy companies to market in the U.S.

Mr. McDermott said he thinks the federal government should match its oil and gas subsidies with similar aid for solar and other renewable-energy technologies, at least at first. “We’re missing the opportunity to become the market,” he said.

Another reason the U.S. is not the top market is its culture, said Mr. Green. European countries, as well as Japan, generally place higher value on the environment, he said.

“Have you ever stayed at a hotel in the United States where you have to put your room key in a box to turn your power on?” he said at the panel. “And then when you leave the room and take the key, the power turns off.”

Nobody in the audience raised a hand. “I’ve done this experiment at panels all over the country, and you get maybe one person,” said Mr. Green. “But it happens all the time in Europe. It’s not a technology difference.” Later, he added: “We just don’t think with that design element.”