A report by Synapse Energy Economics for the Massachusetts Clean Peak Coalition suggests that Massachusetts can fully decarbonize peak generation by 2050 at a lower cost than continuing to run fossil-fuel peaker plants. The report recommends a portfolio of clean peaking resources including demand-side resources, energy storage, and wind generation. Challenges remain in fully decarbonizing the electricity system, particularly with the shift to a winter-peaking system and the current design of ISO New England's capacity market favoring fossil-fuel generators. The coalition is unsure if recent changes to the grid operator's capacity accreditation model will benefit decarbonization efforts in Massachusetts, but a peak generation portfolio combining wind, energy storage, and demand response could serve winter peaks at a lower cost than the current combustion-dominated generation mix. Regulators and policymakers need to focus on energy efficiency, longer-duration energy storage, addressing community concerns around wind siting, and considering climate and public health impacts to build this portfolio cost-effectively and explore alternatives to fossil peakers and combined heat and power plants.