Our model evaluated over 28 billion combinations of renewables and storage, each tested over 35,040 h (four years) of load and weather data. We find that the least cost solutions yield seemingly-excessive generation capacity—at times, almost three times the electricity needed to meet electrical load. This is because diverse renewable generation and the excess capacity together meet electric load with less storage, lowering total system cost. At 2030 technology costs and with excess electricity displacing natural gas, we find that the electric system can be powered 90%–99.9% of hours entirely on renewable electricity, at costs comparable to today's—but only if we optimize the mix of generation and storage technologies.
Source: Cory Budischak, DeAnna Sewell, Heather Thomson, Leon Mach, Dana E. Veron, Willett Kempton, "Cost-minimized combinations of wind power, solar power and electrochemical storage, powering the grid up to 99.9% of the time," Journal of Power Sources, Volume 225, 1 March 2013, Pages 60–74 http://dx.doi.org/10.1016/j.jpowsour.2012.09.054 http://www.sciencedirect.com/science/article/pii/S0378775312014759 [verified 4/17/14]