In July of 2015, two dozen experts met in Cambridge, Massachusetts to consider lessons from a suite of studies on strategies for developing electric systems that are decarbonized, reliable, and affordable. The workshop, sponsored by the Clean Air Task Force and the Energy Innovation Reform Project, found that 1) Near-total decarbonization of the electricity sector should be the primary goal for policymakers. This requires a focus on the long-term transition of energy systems, rather than short-term policies and narrow preferences for particular technologies. 2) Effective and affordable decarbonization of the power sector will require building a reliable and integrated system of multiple low-carbon technologies. 3) Current business investments, policy decisions, and research and development can facilitate the development of a zero-carbon future—but they can also lead to dead ends that constrain or prevent future progress. 4) Technological advances and system adaptations have increased our ability to integrate variable generation sources such as solar and wind. However, the best available information and analysis indicates there are important technical and economic constraints on the extent to which variable resources can be used to achieve the required level of zero-carbon supply. 5) Avoiding low-carbon dead ends will require the pursuit of a diverse portfolio of low-carbon resources and technologies, including a mix of variable and fully dispatchable generation resources. Innovation is urgently needed to develop more options for affordable, dispatchable, synchronous zero-carbon power sources that will be required in a nearly completely decarbonized power system.