NorthWestern Energy (Montana) interconnection application

NorthWestern Energy (Montana) is an investor-owned utility serving 334,012 residential customers in Montana, Wyoming (EIA-861, 2025). Applications: PDF + email (Level 1 Small Generator Facility Interconnection Request to Interconnection Department (hand delivery, mail or e-mail)). Gridpol files NorthWestern Energy (Montana) interconnection applications for licensed installers – solar, storage and EV chargers – with single-line diagram and site plan, unlimited for $500 a month.

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Process verified from NorthWestern Energy (Montana)’s official sources (see below). Wyoming service territory not researched separately (WY has its own tariff); verify for WY projects.

NorthWestern Energy (Montana) at a glance

Utility

NorthWestern Energy LLC (NorthWestern Energy Group)

Type

Investor-owned utility

EIA utility ID

12825

Residential customers

334,012 (EIA-861, 2025)

Net-metered residential customers

11,386 (EIA-861, 2025)

Service territory

36 counties in Montana, 2 counties in Wyoming

How to apply

PDF + email – Level 1 Small Generator Facility Interconnection Request to Interconnection Department (hand delivery, mail or e-mail) · official link

Who submits

Applicant must be the NorthWestern customer (or premises owner if customer is tenant) in good standing; installer contact listed on form. Applicant signs the request and Exhibit A.

Export compensation

NEM – Electric Tariff Rule No. 16 Electric Net Metering
Monthly kWh netting; excess balance carried to annual settle-up month chosen by customer, then resets to zero.

Review time (official)

Rule 17: Interconnection Agreement provided within 5 business days after Level 1 approval determination; applicant must return signed agreement within 30 business days or request is withdrawn. Level 2 evaluation within 20 business days after complete request.

Documents NorthWestern Energy (Montana) asks for

Interconnection application formLevel 1 Small Generator Facility Interconnection Request (Rev 1/23); Levels 2-4 separate form Gridpol prepares this.
Single-line diagram (one-line)Site electrical one-line diagram incl. storage device if any Gridpol prepares this.
Site plan / site layoutDetailed site diagram: array, inverter, storage and disconnect locations Gridpol prepares this.
PV module spec sheetManufacturer spec sheets for all certified equipment; component list with certifying entity/standard (IEEE 1547, NRTL)
Inverter spec sheetManufacturer data sheet (string inverter, microinverter or hybrid inverter).
Battery spec sheet (when applicable)Storage nameplate kW plus explanation of charging/discharging/operating plan
Net metering / net billing agreement (when applicable)Exhibit A Net Meter Applicant Information (choose settle-up month Jan/Apr/Jul/Oct), signed
Customer signatureApplicant certification
Interconnection agreementProvided by NorthWestern after Level 1 approval; sign and return within 30 business days
Final inspection sign-offLocal/state electrical permit and inspection approval before connection

How the NorthWestern Energy (Montana) process runs

Submit Level 1 request with $200 fee, line diagram, site map, spec sheets, Exhibit A
Obtain local/state electrical permit in tandem
Level 1 screens; approval
Interconnection Agreement sent (5 BD), signed and returned (30 BD)
Install; external visible lockable AC disconnect within 10 ft of meter
Electrical inspector approval
NorthWestern installs net meter and authorizes interconnected operation

Fees

Fee	Applies to	Note
$200	Level 1 (<= 50 kW AC certified equipment)	Non-refundable processing fee

Utility fees are paid by the installer or customer; they are not part of the Gridpol plan.

Size levels and limits

Level	Up to	Note
Level 1	50 kW	Aggregate generation + storage nameplate AC, certified equipment
Levels 2-4		Separate request form (Rule 17)
Net metering cap	50 kW

Net metered facilities only solar, wind and/or hydro (Rule 16).

Storage, EV and stamps

Battery storage

Level 1 storage must store/discharge only energy produced by the net metering system (no grid charging); customer must demonstrate compliance of charge/discharge functions with Rule 16 before connection.

Common issues the utility lists

AC disconnect more than 10 ft from meter without prior written variance
Customer not in good standing
Storage charging from grid on Level 1 net-metered system

Gridpol’s pre-submission check covers these before we file.

Sources

NorthWestern Energy Level 1 Small Generator Facility Interconnection Request Rev 1/23: https://northwesternenergy.com/docs/default-source/default-document-library/clean-energy/environmental-projects/private-generation/level-1-small-generator-interconnection-request.pdf (retrieved 2026-11-13)
NorthWestern Energy Montana Electric Rule 17 Interconnection Procedures: https://www.northwesternenergy.com/docs/default-source/default-document-library/billing-and-payment/rates-and-tariffs/montana/rules/electric/rule-17_e.pdf (retrieved 2026-11-13)
NorthWestern Energy Net Metering & Private Generation: https://northwesternenergy.com/clean-energy/our-environmental-projects/net-metering-private-generation (retrieved 2026-11-13)

Other utilities in Montana

All Montana utilities →

Gridpol Unlimited

$500 / month

Unlimited interconnection applications. 12-month agreement, signed online. The agreement starts the day you sign; first invoice right away, then monthly.

Unlimited interconnection applications
Single-line diagram and site plan for every application
Pre-submission check against the utility’s requirements
Homeowner e-signature link for the authorization
Filing in your utility portal accounts or by the utility’s method
Utility questions, corrections and resubmissions
Follow-up through approval, inspection and PTO
Customer list, exports, API and webhooks

Get started

Applications are typically submitted within 2 business days after complete documents. Utility review times are set by each utility.