CAISO's "Benefits for Participating in EIM, 2016 Q1 Report", published April 30, 2016, finds that each participating balancing authority area (ISO, NV Energy, and PacifiCorp) experienced estimated gross benefits for the quarter totaling $18.90 million. These benefits are consistent with pre-launch projections.
Three categories of benefits are evaluated in the report: more efficient dispatch, reduced renewable curtailment, and reduced flexibility reserves needed in all balancing authority areas.
1. More efficient dispatch: The EIM facilitates transfer capability across the participating balancing authority areas (BAA) which provides lower supply cost. In Q1 2016 ISO exported a significant amount of renewable energy to PacifiCorp and NV Energy, whereas in past quarters ISO mainly imported energy.
2. Reduced renewable curtailment: "The EIM helps avoid renewable curtailment within the ISO, which has both economic and environmental benefits." The total avoided renewable curtailment volume in Q1 2016 was 112,948 MWh, which displaced an estimated 48,342 metric tons of CO2.
3. Reduced flexibility reserves needed: "The EIM facilitates procurement of flexible ramping capacity in the [15 minute market] to address variability that may occur in the [real time dispatch]. Because variability across different BAAs may happen in opposite directions, the flexible ramping requirement for the entire EIM footprint can be less than the sum of individual BAA's requirement." The flexible ramping savings for Q1 2016 was about 35%.
You can read the whole report, including a breakdown of benefits by BAA here.