FERC requests information about MISO’s zero-injection agreement

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FEDERAL ENERGY REGULATORY COMMISSION
WASHINGTON, DC  20426

OFFICE OF ENERGY MARKET REGULATION

In Reply Refer To:
Midcontinent Independent System Operator, Inc.
Docket No. ER26-3552-000

Issued:  October 9, 2026

Midcontinent Independent System Operator, Inc.
720 City Center Drive
Carmel, IN  46032

Attention:  Christopher Supino
	       Managing Senior Corporate Counsel 

Reference:  Deficiency Letter

Dear Mr. Supino:

On August 18, 2026, Midcontinent Independent System Operator, Inc. (MISO) submitted proposed revisions to its Open Access Transmission, Energy and Operating Reserve Markets Tariff (Tariff)[fn:2] to establish a 90-day study process, operational requirements, and market and resource adequacy rules to accommodate the interconnection of a Zero Injection Generation Resource (ZG Resource), which is a generating facility that intends to serve load interconnecting at the same substation and voltage level as the ZG Resource without injecting energy onto MISO’s transmission system.[fn:3]  MISO proposes to add a pro forma Zero Injection Generator Interconnection Agreement (ZGIA) to its Generator Interconnection Procedures (GIP), contained in Attachment X of the Tariff, to govern the ZG Resource’s Zero Injection Generation Interconnection Service (ZG Interconnection Service).  MISO also proposes that a ZG Resource may participate in MISO’s markets and resource adequacy construct, subject to the limitation that its participation is limited to serving, and being credited for serving, the load associated with the ZG Resource (ZG Associated Load).  

Please be advised that your submittal is deficient and that additional information is necessary to process the filing.  Please provide the information requested below.

The Commission applies an independent entity variation standard to evaluate regional transmission organization and independent system operator (RTO/ISO) proposals for deviations from the Commission’s pro forma Large Generator Interconnection Procedures (LGIP) and pro forma Large Generator Interconnection Agreement established in Order No. 2003[fn:4] and the Commission’s subsequent final rules on generator interconnection, including Order No. 2023.[fn:5]  Under the independent entity variation standard, an RTO/ISO must demonstrate that its proposed variations are just and reasonable and not unduly discriminatory or preferential and accomplish the purposes of Order No. 2003 and the Commission’s subsequent final rules on generator interconnection.  Please explain how the proposed revisions to MISO’s GIP accomplish the purposes of Order No. 2003 and the Commission’s subsequent final rules on generator interconnection. 

The proposed definition of “ZG Interconnection Service” in Module A of the Tariff, MISO’s GIP (including GIP section 3.2.5.1), and Articles 1 and 4.1.4.2 of MISO’s pro forma ZGIA each generally state, in relevant part, “ZG Interconnection Service does not grant any right to inject energy onto the Transmission System beyond the Point of Interconnection except as may be authorized by Section 3.11 of [this GIP].”[fn:6]

However, proposed GIP section 3.11 (Additional Requirements for Interconnection Requests Seeking ZG Interconnection Service) includes specific technical, deadline, and other requirements for such interconnection requests,  and GIP section 3.11.1(a) does not exist in the proposed or currently effective Tariff.  Please clarify the references to GIP sections 3.11 and 3.11.1(a) in the proposed Tariff language cited above.

Pursuant to GIP section 3.4.1, MISO must post certain information about each interconnection request on its Open Access Same Time Information System or website, including “associated Interconnection System Impact Study phase costs by Definitive Planning Phase” for interconnection requests in MISO’s traditional generator interconnection study process.[fn:7]  This section implements the public posting requirements contained in section 3.5.1 (OASIS Posting) of the Commission’s pro forma LGIP.[fn:8]  Please clarify whether MISO intends to publicly post any results from ZG Interconnection Service studies, including any associated network upgrades at the point of interconnection and interconnection facility costs, and, if so, please identify any currently effective or proposed Tariff provisions that would be applicable to such posting.  To the extent that MISO does not intend, under its proposal, to publicly post such information in alignment with the Commission’s public posting requirements, please explain why such a proposal meets the independent entity variation standard.[fn:9]

MISO proposes to revise the definitions of “Forecast Maximum Limit,” “Hourly Economic Maximum Limit,” “Hourly Economic Maximum Discharge Limit,” “Hourly Emergency Maximum Limit,” “Hourly Emergency Maximum Discharge Limit,” “Hourly Regulation Maximum Limit,” and “Hourly Regulation Maximum Discharge Limit” to limit the megawatt (MW) level that ZG Resources may offer into MISO’s day-ahead and real-time energy markets, as applicable within each definition, to “less than the Demand of the Resource’s ZG Associated Loads.”[fn:10]  

However, MISO proposes in GIP section 3.11(v) and Article 4.1.4.1 of its proposed pro forma ZGIA that a ZG Resource may receive ZG Interconnection Service and be dispatched at a level that shall not “exceed” the demand of the ZG Associated Load.[fn:11]  Additionally, MISO states that ZG Resources are required to submit maximum limit offers that are at most equal to the demand of the ZG Associated Load and that the subsequent dispatch instructions from MISO will be less than or equal to the offsetting demand of the ZG Associated Load.[fn:12]  

Please clarify whether a ZG Resource’s offers into MISO’s day-ahead and real-time energy markets must be less than the demand of the ZG Associated Load or if the ZG Resource’s offers into MISO’s day-ahead and real-time energy markets may be equal to the demand of the ZG Associated Load, if such ZG Resource also has an amount of ZG Interconnection Service equal to such demand.

MISO proposes to revise section 69A.4.1 of Module E-1 in the Tariff to state, in relevant part, that the Seasonal Accredited Capacity (SAC) for a ZG Resource will be determined based on its participation type, as set forth elsewhere in the section, and will be capped at the specified portion of the coincident peak demand forecast attributable to the ZG Associated Load.[fn:13]  Additionally, beginning in the 2028/2029 planning year, MISO will assign SAC values to capacity resources through a two-step process using class-level accreditation for each resource class (e.g., gas, solar, wind) and resource-level information on each resource’s demonstrated availability.[fn:14]  MISO also proposes to revise section 69A.3.1.g of Module E-1 to add “[t]he amount of ZG Interconnection Service under Attachment X only for a ZG Resource” to the list of factors, in sub-section A, that MISO uses to determine the deliverable amount of generation resources, electric storage resources, and external resources, as well as a similar list of factors in sub-section B used for determining the deliverable amount of intermittent generation, dispatchable intermittent generation, and electric storage resources.[fn:15]  MISO explains that the nature of the proposed revisions to Module E-1 reflect the fact that a ZG Resource cannot serve load in the MISO region beyond the substation and voltage level of its co-located ZG Associated Load.[fn:16]

Please explain why it is just and reasonable to assign a SAC for a ZG Resource, which cannot inject beyond its point of interconnection, using the currently effective method based on participation type and the method based on resource class going into effect for the 2028/2029 planning year.   

Under MISO’s proposal, a capacity resource with 100 MW of Network Resource Interconnection Service would be considered equally deliverable to load as a ZG Resource with 100 MW of ZG Interconnection Service.  Given that a ZG Resource cannot serve load in the MISO region beyond the substation and voltage level of its co-located ZG Associated Load, please explain why it is just and reasonable to consider these two resources as equally deliverable to load.  In addition, please explain how such a deliverability determination would impact conversion of the ZG Resource’s SAC to zonal resource credits for each resource type, as applicable, which load-serving entities may use to meet their resource adequacy requirements.  

To address situations in which there is a reduction or loss of load by the ZG Associated Load, MISO proposes to revise its GIP to define “Transient Tolerance Window” as follows:

Transient Tolerance Window shall mean the period of time after a reduction or loss of load by the ZG Associated Load by the end of which window the Generating Facility with ZG Interconnection Service must have reduced its injections to an amount not greater than the Load of the ZG Associated Load. The Transient Tolerance Window shall be no greater than 20 seconds, and is further described by the Business Practices Manual
for Large Load. The Transient Tolerance Window will be subject to Transmission Owner local planning criteria.[fn:17]
	
MISO states that it determined that a 20-second limit provides the best system-wide balance between what is technically feasible and commercially practical while minimizing even transient injections.  MISO further states that there may be circumstances where a narrower window is necessary and practical given electrical topology on certain parts of the MISO system or applicable local planning criteria.[fn:18]

Please explain how MISO and the applicable transmission owner will establish the Transient Tolerance Window applicable to each ZG Resource, including the circumstances in which it would require a window shorter than 20 seconds.  Please also explain the basis upon which MISO will apply shorter windows (e.g., on a transmission owner basis or individual ZG Resource basis).  Please also identify where any narrower window applicable to an individual ZG Resource will be documented.

Please explain how MISO will evaluate, in the ZG Impact Assessment, the amount, in MW, of injections during the Transient Tolerance Window and how it will determine that such amount will not cause adverse reliability impacts.

MISO proposes that ZG Interconnection Service is only available to an interconnection customer if the proposed interconnection will not require the construction or modification of network upgrades, with the exception of network upgrades located at the same substation as the point of interconnection or System Protection Facilities at adjacent substations.[fn:19]

Please explain what constitutes an “adjacent” substation for purposes of this exception.

Please explain whether the “obligations to implement equipment and/or operational procedures to prevent injections onto the Transmission System beyond the substation where the ZG Resource and ZG Associated Load are located” include procedures to address the failure of control equipment or associated communications.  Please identify any applicable Tariff provisions. 

Please explain the contingency scenarios that MISO will study in the ZG Impact Assessment, including whether and how MISO will evaluate a scenario involving a sudden trip of a ZG Resource while its ZG Associated Load remains in service.  

Please clarify whether the use of the lowercase term “system protection facilities” in proposed GIP section 3.11(ii) is intended to refer to the defined term “System Protection Facilities.”[fn:20]

Please clarify whether the use of the term “ZG Impact Analysis” in proposed GIP sections 3.11.2 and 3.11.3 is intended to refer to the proposed defined term “ZG Impact Assessment.”[fn:21]

Please clarify whether the use of the lowercase term “point of interconnection” in Article 9.7.4.7(c) of the proposed pro forma ZGIA is intended to refer to the defined term “Point of Interconnection.”[fn:22]

This letter is issued pursuant to 18 C.F.R. § 375.307 (2025) and is interlocutory.  This letter is not subject to rehearing pursuant to 18 C.F.R. § 385.713 (2025).  A response to this letter must be filed with the Secretary of the Commission within 45 days of the date of this letter by making a deficiency filing in accordance with the Commission’s electronic tariff requirements.  For your response, please use Type of Filing Code 180, Deficiency Filing.[fn:23]  The information requested in this letter will constitute an amendment to your filing, and a new filing date will be established.[fn:24]  A notice will be issued upon receipt of your filing.

Failure to respond to this letter within the time period specified may result in a
further order rejecting your filing.

Issued by:  Natalie Y. Tingle-Stewart, Director, Division of Electric Power Regulation – Central

Footnotes
[fn:2] Capitalized terms not otherwise defined herein have the meanings ascribed to them in the Tariff or proposed Tariff revisions.
[fn:3] Transmittal at 1.
[fn:4] Standardization of Generator Interconnection Agreements & Procs., Order          No. 2003, 104 FERC ¶ 61,103, at P 827 (2003), order on reh’g, Order No. 2003-A, 106 FERC ¶ 61,220, order on reh’g, Order No. 2003-B, 109 FERC ¶ 61,287 (2004), order on reh’g, Order No. 2003-C, 111 FERC ¶ 61,401 (2005), aff’d sub nom. Nat’l Ass’n of Regul. Util. Comm’rs v. FERC, 475 F.3d 1277 (D.C. Cir. 2007).
[fn:5] Improvements to Generator Interconnection Procs. & Agreements, Order No. 2023, 184 FERC ¶ 61,054, at P 1764 & n.3346, order on reh’g, 185 FERC ¶ 61,063 (2023), order on reh’g, Order No. 2023-A, 186 FERC ¶ 61,199, errata notice, 188 FERC ¶ 61,134 (2024), aff'd sub nom. Advanced Energy United v. FERC, No. 23-1282 (D.C. Cir. July 31, 2026).
[fn:6] MISO, Proposed Tariff, Module A, § 1.Z (Definitions Z) (43.0.0); id., attach. X (190.0.0), §§ 1 (Definitions), 3.2.5.1 (The Product); id., app. 19 (31.0.0), art. 1 (Definitions); id., art. 4.1.4.2 (Transmission Service Delivery Implications), citing specifically to section 3.11.1(a) of the GIP.
[fn:7] MISO, Tariff, attach. X (183.0.0), § 3.4.1.
[fn:8] Pro forma LGIP § 3.5.1.
[fn:9] See supra notes 3 and 4.
[fn:10] MISO, Proposed Tariff, Module A, § 1.H (Definitions H) (63.0.0) (emphasis added).
[fn:11] Id., attach. X (190.0.0), § 3.11(v); id., app. 19 (31.0.0), art. 4.1.4.1 (The Product).
[fn:12] Transmittal, Tab C (Prepared Direct Testimony of Marc Keyser) (Keyser Test.) at 38-39.
[fn:13] MISO, Proposed Tariff, Module E-1, § 69A.4.1 (Seasonal Accredited Capacity of Capacity Resources) (43.0.0).
[fn:14] MISO, Tariff, Schedule 53A (34.0.0).
[fn:15] MISO, Proposed Tariff, Module E-1, § 69A.3.1.g (Determination of Deliverability) (44.0.0).
[fn:16] Transmittal at 19.
[fn:17] MISO, Proposed Tariff, attach. X (190.0.0), § 1 (Definitions).
[fn:18] Transmittal at 21.
[fn:19] MISO, Proposed Tariff, attach. X (190.0.0), § 3.2.5.1 (The Product); id., app. 19 (31.0.0), art. 4.1.4.1 (The Product).
[fn:20] Id., § 3.11 (Additional Requirements for Interconnection Requests Seeking ZG Interconnection Service).
[fn:21] Id., §§ 3.11.2 (Evaluation Process for ZG Interconnection Service Interconnection Requests), 3.11.3 (ZG Interconnection Service - Notice to Proceed).
[fn:22] Id., app. 19 (31.0.0), art. 9.7.4.7.
[fn:23] Elec. Tariff Filings, 130 FERC ¶ 61,047, at PP 3-8 (2010) (stating that an amendment filing must include at least one tariff record even though a tariff revision might not otherwise be needed).
[fn:24] See Duke Power Co., 57 FERC ¶ 61,215, at 61,713 (1991) (“[T]he Commission will consider any amendment or supplemental filing filed after a utility’s initial filing . . . to establish a new filing date for the filing in question.”).

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