As of the end of 2018, 29 states and the District of Columbia had adopted renewable portfolio standards (RPS), polices that require electricity suppliers to source a certain amount of their electricity from designated renewable resources or eligible technologies. Three states—Maine, New York, and Ohio—have updated their RPS since May 2019. As a result of their updates, Maine and New York joined California, Hawaii, Nevada, New Mexico, and the District of Columbia in requiring 100% clean electricity by 2050.

The 29 states and the District of Columbia that have legally binding RPS policies in place collectively accounted for 63% of U.S. electricity retail sales in 2018. Another eight states have established nonbinding renewable portfolio goals.
In addition to establishing which technologies qualify to meet each state’s renewables standard, states have defined terms such as carbon-free, carbon-neutral, or clean energy in different ways. For example, some states may allow technologies such as nuclear or natural gas with carbon capture and storage to count toward policy targets. Other states have left implementation to regulatory processes and do not yet have formal guidelines on what qualifies to meet the targets.
Maine increased its overall RPS target in June 2019 to 100% of electricity sales from renewable generation by 2050, up from the previous target of 10% renewable generation by 2017.
Also in June 2019, New York increased its overall RPS target to 100% of electricity sales from clean energy generation by 2040, with an interim target of 70% renewable generation by 2030. This new target was an increase from the previous target of 50% renewable generation by 2030.
In July 2019, the Ohio legislature passed legislation decreasing its RPS to 8.5% of electricity sales from renewable generation by 2026 from the previous target of 12.5% by 2026. Ohio is the first state in the past decade to reduce or repeal its RPS target since Kansas repealed its RPS in 2009.
In January 2019, the District of Columbia increased its RPS target to 100% renewable electricity sales by 2040.