The “next generation” electric utility must incorporate variable renewable resources, including wind and solar, in much larger quantities than conventionally thought possible. While resource variability presents a challenge, it should be possible to reduce and manage that variability by geographically distributing renewables, combining them with different renewables, and having more dynamic control of electric loads. This study shows that interconnecting individual solar generation sites into geographically diverse arrays can reduce power output variability, and that including solar generation sites in arrays of geographically diverse wind sites can further reduce the total variability beyond what is possible for either resource type alone. Specifically, optimized portfolios offer an average decrease in variability of 55% below the average of all individual sites. Finally, it was observed that, in the modeled system, only a small subset of the potential sites in an interconnected array need to be included to achieve these variability reductions.