Suppose for a moment that it is 2050. Suppose, too, as increasingly seems to be the expectation in the energy sector, roughly half of the world’s total energy consumption is supplied by solar energy. That would require something like 100 TW of peak solar capacity, or 227 billion solar panels, roughly 29 panels per person on the planet. Who owns those 227 billion panels? It is literally a $100 trillion question, and one of the most consequential design choices confronting humanity in the coming energy transition. At one extreme, solar ownership might be spread broadly across the world’s nearly 8 billion people. At the other extreme, a small number of owners—whether public or private—could control most of the world’s solar energy supply. In between, are hundreds of different ways of configuring answers to who will own the world’s future solar panels. At stake in the future of energy ownership, I propose in this chapter, is not merely a vast economic resource but the character of political economy and democracy in the 21st century and beyond. Energy is constitutional of social, political, and economic order. As humans, the ways in which we work, move around, and exercise power are all tightly bound up with how we produce, organize, and use energy. As such, energy transitions are never just shifts in technology or fuel source but always also transformations of society and markets.