20 w 30 w 6 w 0双 .2 03 碳 06 文 0. 库 vi p THE U.S. AND CHINA NEED D E C A R B O N I Z I N G T H E P OW E R S E C T O R TO REDUCE METHANE EMISSIONS, IN THE U.S. AND CHINA S U B STA N T I A L LY A N D CO L L A B O R AT I V E LY DECARBONIZING THE POWER SECTOR IN THE U.S. AND CHINA  Mike O’Boyle, Energy Innovation* Max Dupuy, Regulatory Assistance Project* * Organizations are noted for affiliation purposes only. This paper represents authors’ views, and not necessarily those of their institutions. KEY ISSUES AND TRENDS 20 w 30 w 6 w 0双 .2 03 碳 06 文 0. 库 vi p Together, the United States’ and Chinese power systems emitted 5,780 million metric tons of carbon dioxide equivalent (CO₂e) in 2020, about 36% of the two countries’ and 17% of the world’s annual carbon emissions (International Energy Agency 2022). Consensus is growing among the scientific community that majority renewables-based electricity systems exceeding 80% carbonfree can be operated reliably and at low cost, without developing new technologies (Abhyankar et al. 2022; MacDonald et al. 2016; Novacheck, Brinkman, and Porro 2018; NREL 2012; Phadke et al. 2020). The U.S. and China face similar physical and policy challenges to transform their power sectors, despite different economic and institutional conditions. The transition to a renewablesbased electricity system is also essential for decarbonizing end-uses – such as transportation and heating of buildings – through electrification. The Nationally Determined Contributions (NDC) of both countries under the United Nations Framework Convention on Climate Change include significant power sector commitments. Figure 1 | U.S. and China Electricity Sector Greenhouse Gas Emissions, 2000-2019. Data source: Climate Watch (https://www.climatewatchdata.org/ghg-emissions?end_year=2019&regions=CHN%2CU SA&sectors=electricity-heat&start_year=1990) 1 However, given that neither country’s NDC pledges for 2030 are sufficient to support a 1.5 degrees C pathway, and given the centrality of the power sector to decarbonization efforts, both must consider redoubling efforts to reduce power sector emissions. The good news is that wellunderstood and feasible policy pathways, applicable to both countries, can improve reliability and help reduce costs while accelerating the power sector transformation. The U.S. recently committed to reducing economy-wide net greenhouse gas emissions by 50% below 2005 levels by 2030, a zero-carbon power sector by 2035 and a net-zero emissions economy by no later than 2050. The U.S. electricity sector must reduce emissions approximately 80% below 2005 levels by 2030 in order to meet the 2030 national target (Abhyankar et al. 2021; Larsen et al. 2021; Larson et al. 2021). While the U.S. electricity sector has substantially reduced emissions from its peak in 2005, and is currently 40% carbon-free, reaching 80% carbon-free in 2030 and 100% in 2035 would represent a dramatic acceleration of clean energy deployment and fossil retirement. Sector experts widely agree that meeting these targets is possible, would markedly improve public health, create new jobs, and even potentially reduce consumer electricity costs (Abhyankar et al. 2022). However, doing so will require additional policy, including new federal regulation and sub-national action. 20 w 30 w 6 w 0双 .2 03 碳 06 文 0. 库 vi p U.S. efforts at the federal and sub-national levels are evolving. Twenty-one states plus the District of Columbia and Puerto Rico, representing one-third of electric generation, have set goals for 100% clean electricity, although many of these are 2050 goals, not 2035 as in the U.S. national commitment.1 39 of the 41 largest utilities in the U.S. have made public commitments to hit net zero emissions by midcentury (Esposito and Jeffrey 2022). The U.S. passed a major infrastructure bill in 2021 which includes funding for end-use energy efficiency and transmission projects (along with provisions to support transmission siting authorization) that will support renewable project development and renewable energy integration. In August 2022, the U.S. passed into law a historic package of federal policies to support economy-wide decarbonization.2 The package includes financial incentives for wind, solar, energy efficiency, energy storage, and electrification of transportation, buildings, and other end-uses. The U.S. Department of Energy estimates that the package will reduce economy-wide emissions to 40% below 2005 levels by 2030. W