The Western Electric Coordinating Council (WECC) engaged E3 to model the benefits of implementing an energy imbalance market (EIM) across the Western Interconnection. Working with WECC staff and many stakeholders, we modeled and compared simulated production costs for a scenario that maintained existing operational arrangements and a second scenario with a consolidated regional balancing market. The analysis found benefits from improved system dispatch, as well as from reductions in operating reserves needed to accommodate wind and solar variability. E3 devised an innovative technique to more accurately estimate the potential impact of the EIM, and pioneered applying “hurdle rates” to calibrate the GridView production simulation base case so that it more accurately reflected bidding and dispatch practices in the West. Since presenting our findings to WECC in 2011, we have developed similar EIM cost-benefit studies for 10 additional utilities.