As news comes out of the climate change conference in Cancun, investors are eager to bet on non-fossil fuel technology.

Energy stock funds were at the bottom of the list this year, according to Morningstar, which may make them an opportunity for clients with the patience and stomach for volatility.

The political moment may be right, too: according to an October report from the Brookings Institution, the American Enterprise Institute, and the Breakthrough Institute, a bi-partisan consensus around American energy policy could emerge as the United States moves past the political stalemate over policies to cap carbon emissions.

But even with no change in policy, a new report from the Pew Charitable Trust projected that there will be 1.7 trillion invested worldwide in clean energy by 2020. With more government support, the number will top 2 trillion.

China and India are leading the way, the Pew report said, with the United Kingdom and Germany leading in Europe. The United States has the potential to attract $342 billion in clean power project investments over the next 10 years with stronger government support, the Pew found.

The Breakthrough report calls for a U.S. government investment of $25 billion a year in clean energy technologies while supporting development of small nuclear reactors.  There’s surprisingly little investment in the United States, considering the public support for a future economy built around green jobs. American energy firms now reinvest less than one percent of their revenues in R&D,  compared to 10 to 20 percent in the information technology, semiconductor, and pharmaceuticals industries. The report also concluded that “federal investments in energy technology — from hydro and nuclear to solar, wind, and electric vehicles — have been an overwhelming success.”

Substantial investment is needed as current green energy is still too expensive, says Bjørn Lomborg, adjunct professor at Copenhagen Business School.  As Lomborg points out, despite Germany’s heavily-subsidized early move to put up solar panels, the sun still provides only 0.1% of its total energy supply.  In Denmark, after an early investment in wind power, the industry remains dependent on subsidies and Danes continue to pay the highest electricity rates of any industrialized nation. Both wind and solar power require large tracts of land. Many areas will need direct-current lines to carry energy long distances and establish reliable storage in order to provide ongoing service. Next generation biofuels cost roughly twice as much as gasoline today and large-scale nuclear power plant remain unpopular and expensive to build.