The Guinness fund has favored solar stocks since 2006, which has dragged the fund down in the past year. The portfolio also has a little exposure to wind power with turbine maker Vestas Wind Systems ( VWDRY). Picking a fund requires investors to predict the direction of alternative energy. If you think solar energy will lead a rebound then the Guinness fund might be the best choice. If you think green technology will take the limelight, the Winslow Green fund might be the way to go. A year ago, I called solar stocks and exchange-traded funds faddish. They had had a great run, but they seemed overextended. After all, solar power won't be affordable for widespread use for years. The companies' stocks have dropped more than the broader market in the past year. Investors need to realize that adding alternative energy companies to a diversified portfolio will create volatility. This helps on the way up, but it will hurt on the way down.