For a utility in the Western U.S., Brattle experts assessed the potential compensating resource needs and costs associated with integrating intermittent resources into the regional system. We designed and managed the development of the first user-interactive evaluation tool to estimate the investment and operational cost associated with increasing regulation, load-following, day-ahead scheduling, and ramping services that will be needed with increasing intermittent resources that have generation output that can be unpredictable and variable in nature. The framework and mechanics of the model have been presented before the California Public Utility Commission’s Stakeholder workshops, with results of scenarios discussed at various forums.