The reduction in climate pollution – even as Congress failed to act on climate change – brings America more than halfway towards Barack Obama's target of cutting emissions by 17% from 2005 levels over the next decade, the Bloomberg analysts said.
By the end of last year, America's emissions of carbon dioxide and other greenhouse gas emissions had fallen 10.7% from the 2005 baselines.
That drop puts Obama in a better position to defend his environmental achievements, which have often gone overlooked in the bitter rows over climate science.
It may also buoy up America's standing in the global climate negotiations.
"There have certainly been some solid results on the board in the US as a result of all these changes," Ethan Zindler, a BNEF analyst said.
Lisa Jacobson, president of the BCSE, said the Bloomberg findings exposed the conservative argument that acting on climate change would be a drag on the economy. Instead, carbon emissions declined even as GDP was going up, she noted.
As described by Bloomberg, the US is in the throes of a major shift in energy production. Coal fell to just 18.1% of America's energy mix last year, down from 22.5% in 2007. Oil use also declined.
The explosion of natural gas production, thanks to fracking, filled much of the gap. America got 31% of its electricity from gas-fired power plants last year.
But the report found steadily expanding installation of wind, solar, hydro and geothermal energy. Renewables represented the largest single source of new growth last year, reaching $44bn in 2012, the report said, the report said.
Over the same time span, total energy use fell since 2007, by 6.4%, the report said. Most of the emissions cuts were due to installing more efficient heating and cooling systems in commercial building.
Other cuts in emission came from transport, with 488,000 Americans last year opting for hybrid and plug-in vehicles.