MISO MTEP-26: $8.8 Billion Transmission Plan Allocates $3.1 Billion for Data Center Load Growth
MISO's draft 2026 Transmission Expansion Plan (MTEP-26) represents a paradigm shift in grid planning for the Midwest. The $8.8 billion portfolio — the largest in MISO history — dedicates $3.1 billion (35%) exclusively to load growth infrastructure, driven overwhelmingly by data center interconnections, industrial reshoring, and electrification. MISO has revised its long-term peak demand compound annual growth rate (CAGR) to 1-2% through 2044, materially higher than the 0.5% flat growth assumed in prior planning cycles. The Expedited Project Review (EPR) pipeline now processes over 13 GW of load additions annually — up from 10 GW approved in 2025. These costs will be socialized across commercial and industrial ratepayers through transmission cost allocation, with the Midwest subregion bearing the largest share.
Executive Impact
- →Transmission Cost Socialization: The $3.1 billion in load growth projects will be allocated across MISO's footprint through its cost-sharing formula. For commercial customers in the Midwest subregion, this could add $0.50-$1.00/MWh to transmission charges beginning in 2028, compounding on top of already-rising capacity costs from the annual PRA auctions.
- →Planning Paradigm Shift: MISO has abandoned its historical "diffuse, linear growth" model. Data center loads now represent "step-change" demand additions — single sites requesting 200-500 MW of firm capacity — that require dedicated substation builds and high-voltage line extensions. This new reality means grid plans are now driven by a handful of major corporate decisions, not aggregate population trends.
- →Capacity Auction Pressure: MISO's 2026/27 PRA results (due April 28) will reflect the supply-demand squeeze that MTEP-26 aims to address over the next decade. The 1.9 GW capacity gap identified in pre-auction data suggests clearing prices will rise materially from last year's Zone 4 cost of $72.84/MW-day.
Inside the $8.8 Billion Portfolio
MTEP-26 is organized into three investment tiers, each reflecting a different urgency and cost-allocation mechanism:
- Local Reliability + Age/Condition ($5.9B): The largest bucket covers traditional grid maintenance — replacing aging transformers, rebuilding deteriorated transmission lines, and reinforcing substations. While mundane, this spend reflects decades of deferred maintenance now converging with record-high load growth.
- Expedited Load Growth Projects ($1.3B): These are fast-tracked projects specifically tied to large load interconnections. The majority serve data center and industrial campus requests in the Midwest subregion. MISO's EPR process has approved nearly 10 GW of load additions since 2025, with another 13+ GW expected to flow through the pipeline in 2026.
- Multi-Value Projects (MVPs): Long-range, high-voltage projects (345 kV+) designed to increase transfer capability between MISO subregions. These are the successors to MISO's $10.3 billion Long Range Transmission Plan (LRTP) Tranche 1 approved in 2022.
How Data Center Demand Reshaped MISO's Forecast
MISO's planning evolution over the past three years tells a striking story. In 2023, the organization assumed flat-to-slightly-declining peak demand through 2040, consistent with the energy efficiency gains that had flattened US electricity consumption for nearly two decades. By 2024, data center requests in Indiana, Michigan, and the Mississippi corridor forced MISO to adopt "scenario-based planning" that treated large load additions as discrete, probabilistic events rather than smooth forecast curves.
Now, in MTEP-26, data center demand has graduated from an alternative scenario to a baseline assumption. MISO's revised peak demand CAGR of 1-2% means the organization expects system peak to grow from approximately 127 GW today to 140-160 GW by 2044 — a 10-26% increase that dwarfs anything the grid has experienced since the industrial expansion of the 1960s.
The geographic concentration makes the impact even more acute. Indiana and Michigan alone account for a disproportionate share of large load interconnection requests, driven by the I-65 and I-69 "Data Center Corridor" where cheap land, low natural disaster risk, and access to both MISO and PJM transmission attract hyperscale developers.
Commercial Rate Impact: The Three Cost Channels
For existing commercial and industrial customers in the MISO footprint, MTEP-26 creates rate pressure through three distinct channels:
1. Transmission Cost Allocation
Under MISO's current cost-sharing formula, the costs of Baseline Reliability Projects are allocated 100% locally, while Multi-Value Projects are socialized 100% across the MISO footprint on a load-ratio share. The $3.1 billion in load growth projects fall into a hybrid category — partially local, partially socialized. For a typical 1 MW commercial load in Illinois, this could translate to $4,000-$8,000/year in incremental transmission charges by 2028-2029.
2. Capacity Auction Tightening
Every new data center that interconnects reduces the available surplus capacity in MISO's Planning Resource Auction. The April 28 PRA results will preview the supply-demand imbalance that MTEP-26 aims to solve over the next decade. If Zone 4 (IL) clearing prices rise above $100/MW-day — up from $72.84 in the prior year — it directly increases the capacity component of commercial electricity bills by $0.50-$1.00/MWh.
3. Congestion Costs
Until the MTEP-26 transmission upgrades are built (3-7 year construction timelines), existing bottlenecks will worsen. Congestion costs in MISO totaled $3.4 billion in 2025 — up 28% from 2024 — and are expected to continue rising as new loads energize ahead of supporting infrastructure. Commercial buyers with locational exposure to constrained interfaces (e.g., the Michigan-Indiana transfer limit) should evaluate basis-hedging strategies.
Action Items for Midwest Commercial Buyers
- Monitor April 28 PRA Results: The MISO 2026/27 capacity auction clearing prices will be the first concrete signal of how data center demand is pricing into your capacity charges. Budget for a 30-50% increase over last year's Zone 4 clearing.
- Audit Transmission Charges: Request a line-item breakdown of your transmission costs from your utility or REP. As MTEP-26 projects enter rate base, these charges will escalate. Understanding your baseline now enables accurate multi-year budget forecasting.
- Evaluate Demand Response: MISO's tightening supply-demand balance increases the value of curtailable load. If your facility can shed 500+ kW during system peaks, demand response enrollment could offset $30,000-$80,000/year in capacity costs depending on clearing prices.
- Long-Term Procurement Strategy: For large commercial loads (5+ MW), explore bilateral PPAs with renewable or gas generators to hedge against the structural rate increases embedded in MTEP-26. These arrangements bypass the auction-driven capacity price entirely.