Chapter 01 · Climate & transitionEnergy & Transition
Clean energy standard (CES)
Definition
An electricity portfolio standard that sets enforceable, typically rising, targets for the share of clean electricity that utilities or retail providers must sell. Unlike a renewable portfolio standard (RPS), a CES is technology-inclusive — crediting nuclear, hydro and potentially fossil generation with CCS alongside renewables — and usually operates through tradable clean-energy credits earned per megawatt-hour of qualifying generation.
References
CES as electricity portfolio standard; broader-than-renewables eligibility; credit-trading compliance; RPS lineage.
Three defining features (enforceable requirement, technology inclusiveness, ambitious targets); design elements; RPS track record (almost half of 2000–2023 renewable additions).
Overview
What it means
The CES is the RPS's climate-era successor: state RPS policies drove nearly half of US renewable capacity additions between 2000 and 2023, and a growing number of states have layered on technology-neutral clean standards aiming at 80–100% clean electricity by 2030–2050.
Key design choices shape outcomes: whether the standard is framed as a share of sales or an emissions-rate reduction; which sources qualify; the point of regulation; credit tracking; and cost-containment off-ramps. Variants appear outside the US as clean-electricity regulations (e. g. Canada's proposed Clean Electricity Regulations). A federal US CES has been repeatedly proposed but not enacted.
How it is used
States design CESs to decarbonise grids while retaining reliability and cost flexibility; utilities comply via build-out, procurement or credit purchases; analysts model CES designs as alternatives or complements to carbon pricing.
Why it matters
Portfolio standards are the workhorse of power-sector decarbonisation; the clean (rather than purely renewable) framing decides whether firm low-carbon sources compete on equal terms.