Brattle Analysis Finds MISO-SPP Planning Process Undervalues Interregional Transmission
In a new white paper prepared on behalf of the Southern Renewable Energy Association (SREA), experts at The Brattle Group examine the 2024–2025 Coordinated System Plan (CSP) conducted by the Midcontinent Independent System Operator (MISO) and Southwest Power Pool (SPP) and identify opportunities to strengthen the evaluation of interregional transmission investments.
The white paper, Enhancing MISO-SPP Interregional Transmission Planning: Recommendations for Coordinated System Plan, concludes that the current CSP study understates the value of interregional transmission, leading to the premature elimination of promising solutions and ultimately increasing costs and risks to ratepayers. In particular, the analysis finds that the CSP considers a narrower range of benefits than MISO and SPP use in their respective regional planning processes and that its production cost modeling does not fully capture the value transmission provides during stressed system conditions.
The white paper recommends MISO and SPP:
- more fully analyze the benefits for all remaining solutions,
- consider total quantified benefits when selecting projects and allocating costs,
- incorporate all quantified benefits into the RTO-to-RTO cost allocation.
- assess whether cost-effective projects should be designed to accommodate future 765 kV operation, and
- strengthen the benefits framework and production cost modeling used in future CSP cycles.
After the white paper was completed, MISO and SPP made hourly energy-price outputs from their market simulations available. Brattle experts then analyzed those data and compared the simulated prices with historical market outcomes across the MISO South–SPP South seam.
The resulting addendum, Analysis of MISO-SPP’s 2024-25 CSP Production Cost Savings Results, finds that the CSP simulations do not fully capture the frequency or magnitude of high-value market conditions observed historically. Based on the analysis, Brattle experts estimate that the production cost savings associated with upgrades between SPP South and MISO South are likely to be approximately two to three times higher than reflected in the CSP simulations.
Together, the white paper and addendum highlight the importance of evaluating a broader range of transmission benefits and ensuring that production cost models adequately reflect the market conditions in which interregional transmission can provide the greatest value.
Principals Michael Hagerty and Johannes P. Pfeifenberger, and Energy Associate Charlotte Ross, authored the white paper and addendum. Both are available below.
