Data vintage: Q2 2026 · Sources: SPP Tariff, Attachment V §7.2–7.6.2 · SPP DISIS Group 2023-A Final Results · ITP10 Completion Data
SPP Cost Allocation Framework
1
Attachment Facilities (Direct)
Generator lead, step-up transformer, revenue metering, and protective relaying. Directly assigned 100% to the project. Range: $2–20M depending on distance to POI and voltage level.
SPP Tariff, Attachment V §7.2
2
Network Upgrades — Substation
Breaker additions, bus extensions, protection upgrades at the interconnecting substation. Directly assigned if the project is the sole trigger. Shared if multiple projects trigger the same upgrade. Range: $3–30M.
SPP Tariff, Attachment V §7.4.2
3
Network Upgrades — Line Additions
New or upgraded transmission lines triggered by the project. If shared among multiple study group members, allocated by SPP's injection shift factor (ISF) methodology. Range: $20M–$250M in congested areas.
SPP Tariff, Attachment V §7.5
4
Interconnection Financial Assurance (IFA)
Posted at GIA execution. Wind: $50/kW. Solar/Storage: $40/kW. Returned upon commercial operation (net of study cost overruns). Forfeited if project withdraws after construction authorization issued.
SPP Tariff, Attachment V §7.6.2
5
DISIS & GIS Study Fees
Non-refundable study fees: DISIS $200k (large gen, ≥10 MW). GIS: $100k additional. Optional IFS: $50k. Total typical study cost: $350k. Study cost applies before NUC is determined — a sunk cost regardless of proceed/withdraw decision.
SPP Tariff, Attachment V §7.3–7.5
Network Upgrade Cost Benchmarks by Technology & Location
| Technology | States / Region | Avg NUC ($/MW) | IFA Rate | Typical Total Project Range |
|---|
| Onshore Wind — Open Area |
ND, SD, WY, MT |
$25,000–$60,000/MW |
$50/kW |
$6M–$35M |
| Onshore Wind — Congested |
OK (SW), KS (NW) |
$80,000–$200,000/MW |
$50/kW |
$20M–$120M |
| Utility Solar — Southern |
OK, TX (pt.), NM |
$35,000–$90,000/MW |
$40/kW |
$8M–$50M |
| Solar + BESS (co-located) |
All SPP regions |
$45,000–$120,000/MW |
$40/kW + $40/kW |
$12M–$65M |
| Standalone BESS |
All SPP regions |
$20,000–$55,000/MW |
$40/kW |
$5M–$28M |
| Gas Peaker |
OK, TX (panhandle) |
$30,000–$80,000/MW |
$40/kW |
$8M–$40M |
ITP Socialization & Generator Reimbursement Policy
ITP Benefit
Integrated Transmission Planning — 100% Socialized
SPP's proactive ITP transmission lines are socialized — costs spread across all load rather than charged to specific generators. ITP10 ($4B) was 100% socialized. Major benefit for wind developers in high-resource areas: NUC drops dramatically once ITP lines are in service.
SPP Tariff, Schedule 12 — Transmission Expansion Cost Sharing
CWIP Mechanism
Construction Work In Progress Allocation
For approved ITP lines, costs flow into CWIP and are socialized during construction — not just after completion. Generators near approved ITP lines can see NUC cost estimates fall in future DISIS groups as the ITP work progresses. Timing matters significantly for queue strategy.
SPP ITP Cost Recovery Framework §3.2
No Reimbursement
Generator NUC — No OATT Credit Stream
Unlike PJM (which has a Network Upgrade reimbursement mechanism through transmission revenues), SPP does not reimburse generators for NUC paid. Costs borne by developer are permanent sunk costs. This affects project IRR significantly — especially for shared upgrades in congested zones.
SPP Tariff, Attachment V §7.5.3
High-Risk Zone
Cost Shock Risk — SW Oklahoma & NW Kansas
Projects in congested OK/KS areas can receive DISIS results showing $150–250k/MW in shared NUC costs. SPP's 2023 DISIS batch for the SW Oklahoma group saw a 72% project withdrawal rate after cost results were published. Due diligence on cluster group composition is critical before entering the queue.
SPP DISIS Group 2023-A Final Results
SPP Interconnection Cost Trends
2019
ITP10 Completed — $4B Approved
SPP approved 30 new transmission lines across Kansas, Oklahoma, and Texas panhandle. Cost 100% socialized. Expected to reduce NUC for wind in KS/OK by 20–40% once lines complete in 2024–2027.
2020
SPP Average NUC: ~$55k/MW Wind, ~$40k/MW Solar
Pre-congestion benchmarks when the Great Plains grid still had significant headroom. Low by national standards — a primary reason SPP attracted the largest wind pipeline in the US during 2018–2021.
2022
SW Oklahoma Congestion Triggers $180k+/MW NUC
Some DISIS study groups in SW Oklahoma saw shared NUC estimates exceed $180,000/MW — more than 3× the 2020 benchmark. 60%+ withdrawal rates in affected groups. Signals end of the low-cost era for congested Oklahoma wind zones.
2023
Average Across All Groups: ~$85k/MW
SPP processed 3 DISIS groups in 2023. Average cost across all groups: ~$85k/MW. Non-congested ND/SD/WY remain below $50k/MW. Congested OK clusters skew the average significantly higher.
2024 — Now
JTIQ Construction Underway — Relief Expected by 2026
JTIQ's 5 seam projects now entering construction phase. Expected to reduce NUC for projects near the SPP-MISO border by ~15% by 2026, as seam capacity expands and dispatch economics improve for eastern SPP wind.
2025
ITP20 Study Launch — $8–15B Expected
SPP launches ITP20, its 20-year transmission expansion assessment. Expected to identify $8–15B in additional transmission needs for the 2045 clean energy vision. Results will shape generator queue economics for the next decade.
2027
ITP10 Final Projects Complete — Full Great Plains Relief
All 30 ITP10 transmission lines expected in service by 2027. Full NUC cost relief for the Great Plains wind corridor. Estimated 15–25% reduction in average NUC for KS/OK wind projects that enter queue after ITP10 completion.