The only sector as prone to booms and busts as old energy is new energy.
The cleantech sector—also referred to as renewable energy or green energy—has experienced intense volatility over the past several years. That's not surprising for a relatively new sector of the economy. Forecasting supply and demand in the early days of any industry is tough. The booms and busts in the cleantech sector, in particular, have offered hedge funds plenty of "short" profit-taking opportunities, while the longer-term-minded green investors have needed a strong stomach to ride out the ups and downs.
But that's the history. What has the attention of the cleantech experts now is how various niches within cleantech have begun to define themselves and, in some cases, offer steadier, less-risky returns than the catchall cleantech sector has been associated with historically. ETFs are one way to investigate and then invest in cleantech stock plays, and it is an investing theme that has a growing audience.