Renewable resources represent an opportunity for environmentally preferred generation of electricity that supports energy security and independence; however integrating renewable technologies is not without challenges. Renewable resources have limitations that can include location, capacity, cost and availability. California is proactive in the implementation of renewable energy through legislation and execution of a Renewable Portfolio Standard. This work explores key challenges to achieving high penetrations of renewables onto California's grid. The Holistic Grid Resource Integration and Deployment (HiGRID) tool has been developed for this analysis and is verified herein. This tool resolves the hourly operation, performance and cost of renewable and non-renewable generation resources. Three renewable deployment strategies are explored including all wind, all solar photovoltaic, and 50/50 mixture. Initially, wind is the preferred candidate from a cost and required installed capacity perspective; however, as the penetration increases excess wind generation encourages installation of solar. The 50/50 case becomes more cost competitive at high renewable penetrations (greater than 32.4%) and provides the highest system-wide capacity factor and CO2 reduction potential. Results highlight the value of optimizing the renewable deployment strategy to minimize costs and emphasize the importance of considering capacity factor and curtailment when representing the true cost of installing renewables. (C) 2012 Elsevier Ltd. All rights reserved.