The US Environmental Protection Agency will given states different targets to meet depending on the carbon intensity of their current power plants.
The power sector would need to reduce carbon dioxide emissions by 25 per cent on average by 2020 and hit the 30 per cent target 10 years later.
Energy-related carbon emissions in the US fell after 2008 because of a shift toward cleaner-burning natural gas and away from coal-fired plants, and the severe economic downturn.
Emissions in 2013 were already slightly more than 10 per cent below 2005 levels, meaning the US is already well down the road to meeting to new targets.
As well as improving the efficiency of power plants and using sources such as nuclear and renewables, states are also expected to be allowed to use emissions trading systems to comply.