A photo released by Tesla shows its new Powerwall lithium-ion battery pack mounted on the wall (left) of a garage behind one of the company's electric cars. Tesla Energy hide caption

itoggle caption Tesla Energy

Leo Thompson stands in front of his isolated home, where he has lived for 35 years, on the Navajo Nation reservation. Like an estimated 18,000 Navajos homes, his his isn't connected to the electrical grid — it's a half-mile from the nearest line — and until recently Thompson used a generator for power. Ibby Caputo for NPR hide caption

itoggle caption Ibby Caputo for NPR

Renewable energy sources — such as the Eolo wind park about 75 miles south of the Nicaraguan capital, Managua — generate about half of the country's electricity. Officials predict that figure could rise to 80 percent within years. Inti Ocon/AFP/Getty Images hide caption

itoggle caption Inti Ocon/AFP/Getty Images

Without horsepower, they rely on human power: Mother and daughter-in-law Sheela and Sunita Devi shred sugarcane into feed. Ibrahim Malik for NPR hide caption

itoggle caption Ibrahim Malik for NPR

Elizabeth Ebinger in Maplewood, N.J., bought her solar panels, while neighbor Tim Roebuck signed a 20-year lease. Both are happy with the approach they took, and both are saving money on energy bills. Jeff Brady/NPR hide caption

itoggle caption Jeff Brady/NPR

A worker installs solar panels atop a government building in Lakewood, Colo. The industry has added more than 80,000 jobs since 2010, according to The Solar Foundation. John Moore/Getty Images hide caption

itoggle caption John Moore/Getty Images

Solar energy panels on a roof in Marshfield, Mass. Stephan Savoia/AP hide caption

itoggle caption Stephan Savoia/AP

Vera Cole is president of the Mid-Atlantic Renewable Energy Association, a group arguing against proposed rules in Pennsylvania that would put stricter limits on how much grid-connected solar power homeowners can produce on their property. Jeff Brady /NPR hide caption

itoggle caption Jeff Brady /NPR

In Del Norte, Colo., Public Works Supervisor Kevin Larimore shows off solar panels that provide electricity for the town's water supply. Despite generating its own solar energy, the town is still at risk of a blackout if its main power line goes down. Dan Boyce/Inside Energy hide caption

itoggle caption Dan Boyce/Inside Energy

Solar sponge: The top layer of graphite soaks up the sun's energy in tiny holes. When drops of liquid fill the holes, the water quickly evaporates. (The beaker looks hot, but the water below the sponge is cool as a cucumber.) Courtesy of George Ni/MIT hide caption

itoggle caption Courtesy of George Ni/MIT