This essay notes some of the key institutions created in the twentieth century for the purpose of delivering energy in North America. Those institutions are being challenged by a combination of stresses in three interconnected areas: reliability, economics, and environmental sustainability. The essay argues that these three stresses create an “energy trilemma” requiring institutional reform. We suggest that new and modified institutions can best be understood if we evaluate them along three dimensions: institutional scale, structure, and scope. We consider real-world examples of recent institutions in light of each of these dimensions and note both successes and concerns that those factors illuminate. We conclude by noting that some institutional changes will be organic and unplanned; but many others, including responses to climate change, will benefit from conscious attention to scale, structure, and scope by those engaged in designing and building the energy institutions needed in the twenty-first century.