At high penetration of solar generation there are a number of challenges to economically integrating this variable and uncertain resource. These include the limited coincidence between the solar resource and normal demand patterns and limited flexibility of conventional generators to accommodate variable generation resources. Of the large number of technologies that can be used to enable greater penetration of variable generators, concentrating solar power (CSP) with thermal energy storage (TES) presents a number of advantages. The use of storage enables this technology to shift energy production to periods of high demand or reduced solar output. In addition, CSP can provide substantial grid flexibility by rapidly changing output in response to the highly variable net load created by high penetration of solar (and wind) generation. In this work we examine the degree to which CSP may be complementary to PV by performing a set of simulations in the U.S. Southwest to demonstrate the general potential of CSP with TES to enable greater use of solar generation, including additional PV.