Renewable electricity capacity reached 15.5% of the total installed electricity capacity in the US by the end of 2014, according to a report by the National Renewable Energy Laboratory. Installed capacity exceeded 179 gigawatts, generated 554 terawatt-hours.
NREL produced the 2014 Renewable Energy Data Book to "provide useful insights for policymakers, analysts, and investors," NREL Energy Analyst Philipp Beiter said in a statement.
The NREL team found that hydropower made up the vast majority of renewable electricity generation in 2014, followed by wind.
Although solar generation still made up a small mix of the renewables, at 6%, it accounted for 22% of total electricity capacity added in 2014.
Solar was one of the fastest-growing renewables during 2014, with California setting a record for solar power generation in March 2014 and nearly doubling its solar production in less than one year.
Renewables as a whole made up more than half of total electricity capacity added in 2014, with natural gas accounting for 47% of addition, and coal 1%.
Since 2004, renewable electricity capacity has grown 83%, from 98 GW to more than 179 GW in 2014. Even when hydropower is not included, renewable electricity generation has more than doubled since 2004.
With states implementing targets for renewables, such as California's goal of hitting 50% renewable electricity by 2030 and Hawaii's goal of 100%, as well global negotiations around climate change taking place this month Paris, renewables are likely to continue to grow.
In fact, according to the NREL report, investments in renewables grew in 2014 after two years of decline. In the US, investment in clean energy grew 11% to $40.8 billion in 2014, with wind and solar the biggest beneficiaries of those investments.
Of course there are still a number of factors pushing back on renewables' growth. The price of oil is falling and is predicted to stay low through 2016, utilities have started pushing back against the proliferation of rooftop solar by proposing transmission usage fees on customers, and of course the US's future political environment is uncertain.