Renewable energy was the biggest source of new power added to United States electricity grids last year as falling prices and government incentives made wind and solar increasingly viable alternatives to fossil fuels.
Developers installed 16 gigawatts (Gw) of clean energy in 2015, or 68 per cent of all new capacity, Bloomberg New Energy Finance (BNEF) said in its Sustainable Energy in America Factbook released with the Business Council for Sustainable Energy.
The biggest growth came from wind farms, with 8.5Gw of new turbines installed as developers sought to take advantage of a federal tax credit that was due to expire at the end of 2016; Congress extended it in December.
“System costs have really come down for renewable energy, which makes the case for installing them a lot stronger,” she added.
Demand for energy, meanwhile, flat lined in the US last year, holding steady even as the gross domestic product grew 2.4 per cent, BNEF said.
Since 2007, US energy consumption has dropped 2.4 per cent while GDP has grown by 10 per cent.
US clean-energy investments rose to US$56 billion last year, up 7.5 per cent from 2014.
The majority, US$30.2 billion, went to solar, but investors pumped US$11.6 billion into wind energy and US$11.1 billion into technology to improve grids, boost efficiency, develop storage systems and other ways to better manage power usage.
Power from natural gas-fired plants accounted for 25 per cent of capacity added to grids last year.
Nearly one third of all electricity in the US is now generated by gas, putting it nearly on par with coal.
A record number of coal plants were shuttered in 2015, with 11Gw of capacity coming off line by the end of October, and plants with another 3.0Gw of capacity expected to close in November and December.
Natural gas, meanwhile, continued to surge.
“It looks good for gas to be a larger share of electricity generation than coal in 2016,” Ms Regan said.