And in September, the Energy Infrastructure Update reports that all new electrical generating capacity was either solar or wind power.
In that month alone, some 433 MW of renewable generating capacity was added, with a total of 300 MW of wind power and 18 solar projects contributing 133 MW.
The latest figures take the totals for the first nine months of 2012 to 4055 MW of new wind capacity (77 projects), 936 MW of solar power (154 projects), 340 MW of biomass (76 projects) and 123 MW of geothermal power (7 projects). In addition, one 3 MW waste heat project and ten water power projects providing 9 MW have come on-line.
The total of 5466 MW for renewables to date even dwarfs that from new natural gas capacity, which totalled only 4587 MW, along with coal (2276 MW), oil and nuclear.
The figures represent a 29% increase in renewable capacity on last year, with renewables now accounting for nearly 15% of total US electricity generating capacity.
The picture is backed up by new figures from the the American Wind Energy Association (AWEA), which show that 2012 has been a record year for the US wind sector reaching 51,630 MW of electrical generation capacity.
So far this year, the AWEA makes the total new wind capacity to be 4738 MW, with a further 8430 MW in development.
The current capacity provides enough power for around 13 million homes, with Kansas, Oregon, Texas, Oklahoma, and Nevada leading the new installations.
"The remarkable expansion of renewable energy's contribution to the nation's electrical supply reflects continuing declines in costs, the impact of state renewable electricity standards, and the mix of tax and other incentives provided by the federal government," says Ken Bossong, executive director of the SUN DAY Campaign, a non-profit research and educational organization promoting sustainable energy.
He warns that proposals to scale back on investments and federal support for renewables generators - namely the production tax credit (PTC) - are "short-sighted and unwarranted".