Braff, W. A.,Mueller, J. M.,Trancik, J. E.
Wind and solar industries have grown rapidly in recent years but they still supply only a small fraction of global electricity. The continued growth of these industries to levels that significantly contribute to climate change mitigation will depend on whether they can compete against alternatives that provide high-value energy on demand. Energy storage can transform intermittent renewables for this purpose but cost improvement is needed. Evaluating diverse storage technologies on a common scale has proved a major challenge, however, owing to their widely varying performance along the two dimensions of energy and power costs. Here we devise a method to compare storage technologies, and set cost improvement targets. Some storage technologies today are shown to add value to solar and wind energy, but cost reduction is needed to reach widespread profitability. The optimal cost improvement trajectories, balancing energy and power costs to maximize value, are found to be relatively location invariant, and thus can inform broad industry and government technology development strategies.