Utility Tariff Analysis · Updated September 2026

NorthWestern Energy's Large New Load Tariff: What It Means for AI Data Centre Siting in Montana

New large loads served from transmission or substation infrastructure are covered today by NorthWestern Energy's existing Schedule GSEDS-2 for customers served directly from a transmission line or qualifying substation, and, pending before the Montana Public Service Commission since March 2026, a proposed dedicated Large New Load Tariff.

NorthWestern Energy's Large New Load Tariff — AI data centre infrastructure

NorthWestern Energy's Large New Load Tariff

MT

NorthWestern Energy

2026.04.023

Regulatory docket / filing reference

New large loads served from transmission or substation infrastructure

Who the tariff applies to

New large loads served from transmission or substation infrastructure are covered today by NorthWestern Energy's existing Schedule GSEDS-2 for customers served directly from a transmission line or qualifying substation, and, pending before the Montana Public Service Commission since March 2026, a proposed dedicated Large New Load Tariff.

Also active in Montana: Montana is already hosting a 1,000 MW Quantica Infrastructure data centre project (500 MW in an initial phase beginning as early as 2026) and a 150 MW Atlas Power Group project in Butte.

Named Projects Already Underway

CustomerLocationDetails
Quantica InfrastructureMontana1,000 MW data centre project; initial 500 MW phase to begin as early as 2026, full expansion by 2030
Atlas Power GroupButte, MT150 MW data centre project, with 75 MW available in 2026

Figures compiled from the Edison Electric Institute's "Large Load Projects and Tariffs" (September 2026) member-company summary and public regulatory filings. Confirm current tariff terms directly with NorthWestern Energy and the relevant state public utility commission before relying on any figure for a capital decision.

Weighing Montana against another state or a Canadian province with a different rate and interconnection picture entirely? Run both sides of the comparison through our licensed AI data centre cost configurator — it applies each jurisdiction's actual power rate, tax treatment and large-load tariff rules to the same seven build configurations.

Model This State on Your Own Site

Every figure above comes from the same power-cost and tariff dataset behind the SCR AI Build Configurator — a licensed, embeddable widget that models seven data centre build configurations against all nine Canadian provinces and all 50 US states plus DC, returning capital expenditure by line item, energy cost, revenue by commercial structure, EBITDA and payback.

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Not ready for an annual licence? A one-time Site Screening Report ($950, one site) runs the same model for a single build without embedding anything.

Frequently Asked Questions

What is NorthWestern Energy's Large New Load Tariff?

New large loads served from transmission or substation infrastructure are covered today by NorthWestern Energy's existing Schedule GSEDS-2 for customers served directly from a transmission line or qualifying substation, and, pending before the Montana Public Service Commission since March 2026, a proposed dedicated Large New Load Tariff.

Why did NorthWestern Energy introduce this large-load structure?

To ensure the cost of new generation, transmission and distribution infrastructure built to serve very large customers, chiefly hyperscale data centres, is paid for by those customers rather than spread across the general rate base of residential and small commercial ratepayers.

What large data centre projects are already active in Montana?

Montana is already hosting a 1,000 MW Quantica Infrastructure data centre project (500 MW in an initial phase beginning as early as 2026) and a 150 MW Atlas Power Group project in Butte.

Does this tariff replace Montana's standard commercial and industrial rates?

No. NorthWestern Energy's Large New Load Tariff sits above NorthWestern Energy's standard commercial and industrial rate schedules and applies specifically to customers that meet or exceed the large-load threshold described above. Smaller commercial and industrial loads continue to be billed under existing rate schedules.

How can I model a Montana data centre build against this tariff and other states?

The SCR AI Build Configurator applies Montana's power cost, tax treatment and large-load tariff rules alongside all other US states and Canadian provinces, so a Montana scenario can be compared line-by-line against any alternative site.