From an article on ThinkProgress:
September was tied for the hottest of any September on record globally. It was also a very hot month for renewable energy in the U.S. According to figures from the Federal Energy Regulatory Commission, wind and solar accounted for all new electricity capacity added to America’s grid in September.
The projects consisted of five wind farms totaling 300 megawatts and 18 solar installations totaling 133 megawatts.