NEW YORK ( TheStreet) -- Clean energy is destined to gain favor in the next decade. Demand for energy will surely increase, but the use of carbon-based fuels will make the planet dirtier. The hard part is knowing which technology to invest in. Solar, wind, geothermal and others are options, though trying to pick the ultimate winner may not appeal to everyone, which is where a broad-based exchange traded fund like iShares S&P Global Clean Energy Index Fund ( ICLN) comes in. The ETF covers a lot of ground. The iShares Web site breaks down the holdings by industry group, which may not tell the whole story. The fund allocates 45% to solar, 33% to producers and transmitters of energy, 15% to wind power as well as a few battery makers and a geothermal company. The U.S. is the largest country in the fund, at 24%, followed by China (solar stocks), 17%, Spain and Germany, 14%, and Norway and Chile each get 5%. There are 12 countries in all. The fund has been volatile since it debuted in June 2008. At its worst, it was down 80% from its peak, compared with about 45% for the S&P 500 Index and about 55% for the Energy Select Sector SPDR ( XLE). All three bottomed in March. But since then, iShares S&P Global Clean Energy is up 70% versus 60% for the S&P 500 and not quite 50% for the Energy Sector SPDR. The iShares fund has a beta of 2.01. (Beta is a measure of volatility wherein the S&P 500 equals 1; the higher the number, the more volatile the fund.) Surprisingly, the ETF yields a relatively high 2.46%, which is attributable to the utility (producers and transmitters) components.