Good energy policy frameworks foreground the capabilities of electric grids in terms of their holistic qualities. A holistic approach to energy problems requires understanding the sequence in which resources are added to the grid, how they interact collectively with other resources on the system, and what constraints and opportunities are produced by those interactions for the entire system. Holism matters because distinct compositions produce qualitatively distinct capabilities, each with different policy problems. A grid that is composed entirely of wind, water and solar, requires different governance and topology than, say, one composed entirely of nuclear and intermittent renewables or other conceivable permutations.