SPP DISIS 2024 Phase 1: $30B in Upgrade Costs Across 260 Projects

On March 13, 2026, Southwest Power Pool (SPP) posted Phase 1 study results for the DISIS 2024 cluster. With 260 projects representing 66.5 GW of proposed generation capacity, DISIS 2024 is the largest interconnection cluster in SPP history, nearly double the size of the 2023 DISIS in both project count and capacity.

The Phase 1 results reveal a total of $30.2 billion in allocated network upgrade costs across the cluster, with a median cost assignment of $375/kW. Developers in this cluster now have 15 business days to determine whether to proceed in the queue or withdraw their request. Based on historical SPP withdrawal patterns, substantial attrition is likely.

DISIS 2024 Cycle Overview

The cluster's unprecedented size is partly by design. The application window was extended by roughly five months following SPP's FERC waiver request. The extension, combined with strong developer interest, produced a cluster more than twice the size of any prior cycle, and the pre-Phase 1 withdrawal rate had already exceeded 30% before a single cost assignment was posted.

Gas comprises the largest share of total active capacity at 17.7 GW across 33 projects. Solar (62 projects, 13.9 GW) and battery storage (74 projects, 13.9 GW) are nearly identical in total capacity. Solar + battery hybrids comprise 43 projects and 10.3 GW. Wind, historically a major resource type in SPP, accounts for just 32 projects and 9 GW, its smallest share of any recent DISIS cluster.

Phase 1 Cost Results

The Phase 1 results reveal a wide dispersion in cost assignments. The median total allocated cost is $375/kW (25th-75th percentile: $205/kW to $816/kW). Mean costs are driven upward by 37 projects assigned above $1,000/kW, with 2 exceeding $2,000/kW. Only about 47 projects were allocated costs below $150/kW, a range associated with low attrition in prior SPP cycles. The roughly 100 projects above $500/kW face materially higher withdrawal risk.

ERIS network upgrades account for roughly 86% of the $30.2B total. POI costs represent an additional 11%. The incremental cost of NRIS service is under 3%, indicating that the ERIS/NRIS decision has limited cost implications at this stage.

What's Driving the Costs

The costliest upgrades are new 765kV and 345kV high-voltage transmission lines across western Oklahoma, Kansas, and the Texas Panhandle. The six most expensive upgrades alone account for $6.5 billion (22% of the $30.2B cluster total) and each affect between 39 and 53 projects. All 44 projects allocated costs from the $1.3B Woodward-Crawfish Draw 765kV line are solar, wind, or hybrid configurations.

Regional Risk Profiles

The geographic distribution of costs across the SPP footprint reveals distinct regional risk profiles. Projects in the western Oklahoma and Texas Panhandle corridor face the highest cost allocations, driven by the need for major new 765kV transmission infrastructure. Eastern SPP projects, particularly gas-fired generation near load centers, face significantly lower costs.

Interactive Geographic Cost Map

Unlock Full Report

Methodology

Cost data is sourced from SPP's publicly posted DISIS 2024 Phase 1 Powerflow and Short Circuit Draft Report workbook (posted March 13, 2026). Project capacity and queue metadata is sourced from SPP's Generator Interconnection queue, maintained by interconnection.fyi. Cost per kilowatt ($/kW) is calculated as total allocated cost divided by nameplate capacity in kW.