"We're approaching this as a very long-term, viable and profitable universe with huge upside potential," Kramer says. "But you just can't do it by riding the horse upwards. My belief is you have to be very nimble and quick to grab opportunities both on the upside and downside."
For investors who aren't into shorting stocks, the best bet is to grab some of the industry leaders--the market's recent downturn brought some of them back to reasonable levels--and be prepared for the long haul. Other options include green tech-focused mutual funds such as the Calvert or Guiness Atkinson offerings, or some of the PowerShares ETFs based on the Cleantech or WilderShares indices.
If green tech is still in the early innings, it's shaping up to be an interesting ball game.