When will cheaper gas threaten alternative energy?

Getting close?

I caught Mario Gabelli on a CNBC special today. Gabelli, Chairman and Chief Executive Officer of GAMCO Investors, Inc made a point of discussing how lower gas prices could have a huge effect on alternative energy stocks. In fact, Gabelli believes that if gas drops below $3.00, it could have a detrimental effect on America's push towards alternative energy policies.

Is green investing headed for trouble?