Geothermal power has a promising future, but so far it has lagged behind most of its other renewable energy cousins, especially wind and solar. So while wind power in the US has grown by 13.2 gigawatts in 2012, with 5.5 gigawatts of that just in December, geothermal's growth is more modest. According to the Geothermal Energy Association, the U.S. added 147.05 MW of gross geothermal power capacity in 2012, which is 5% more than in 2011.

That might not seem like much, but geothermal power has very desirable attributes that make it worth developing further; unlike wind and solar, it generates power 24/7 regardless of the weather. It's true that there are many ways to mitigate the intermittency of wind and solar, including possibly with grid-scale liquid-metal batteries, but having some nice clean baseload power in the mix will always be a good thing. Now the trick is to reduce costs, and to make sure we understand the geology properly to avoid problems.