Plug Power, for example, trades about 539,000 shares a day, which isn't much by Wall Street standards. ExxonMobil, the largest oil company, trades about 6.3 million shares a day. So fuel-cell producers can be erratic, to say the least. Even FuelCell Energy, the best performer of the lot, is hard to bet on. But when you get into alternative energy, that's what you get.
Solar companies are similar.
Trading volume averages just 72,000 shares. Many socially conscious funds simply invest in natural gas companies because natural gas is cleaner than coal or oil. Mark Regier, director of social research at MMA Praxis funds, warns that if you overlook all oil companies, you overlook some opportunities in alternative energy. BP Amoco, for example, has the largest solar energy division in the world. Don't bet everything on small alternative energy companies or you might not have enough left to pay the gas bill.