LEGAL	3 Months Ended
Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]
LEGAL	LEGAL Other than as disclosed below or in Tri-State's annual report on Form 10-K for the year ended December 31, 2025 filed with the SEC, Tri-State does not expect any litigation or proceeding pending or threatened against it to have a potential material effect on its financial condition, results of operations or cash flows. CTP Proceeding: Pursuant to Tri-State's Bylaws, a Member may only withdraw from membership in Tri-State upon compliance with such equitable terms and conditions as Tri-State's Board may prescribe, provided, however, that no Member shall be permitted to withdraw until it has met all its contractual obligations to Tri-State. On September 1, 2021, Tri-State filed with FERC a contract termination payment methodology tariff as Rate Schedule No. 281 that provides a process should a Utility Member elect to withdraw from membership in Tri-State and terminate its wholesale electric service contract, Docket No. ER21-2818. The tariff process includes requirements for a two-year notice and the payment to Tri-State of a contract termination payment. On October 29, 2021, FERC accepted Rate Schedule No. 281, effective November 1, 2021, subject to refund. FERC set the matter for hearing and instituted a concurrent Federal Power Act ("FPA") section 206 proceeding to determine the justness and reasonableness of the methodology. On December 19, 2023, FERC issued an order adopting a modified balance sheet approach for the contract termination payment methodology ("FERC December 2023 Order"). On March 28, 2024, Tri-State filed a petition for review of the FERC December 2023 Order with the United States Court of Appeals for the Tenth Circuit ("Tenth Circuit Court of Appeals"), Case No. 24-9516, related to FERC's rejection of the lost revenue approach and also other items. On May 23, 2024, FERC issued a substantive order on rehearing, which modified the discussion in, but sustained the results of, the FERC December 2023 Order (“FERC May 2024 Order”). On May 31, 2024, Tri-State filed a petition for review of the FERC May 2024 Order, Case No. 24-9538, with the Tenth Circuit Court of Appeals. On June 3, 2024, the Tenth Circuit Court of Appeals issued an order partially consolidating the cases for purposes of briefing. On March 24, 2026, the Tenth Circuit Court of Appeals issued an opinion denying Tri-State's petitions for review and affirming FERC's rejection of the lost revenue approach and FERC's modified balance sheet approach. Tri-State is evaluating further options related to this decision. In 2024, Tri-State filed three revisions to Rate Schedule No. 281 as compliance filings with FERC as directed by applicable FERC orders. On December 5, 2024, FERC issued an order on certain of Tri-State's 2024 revisions of Rate Schedule No. 281, subject to further compliance filing ("FERC December 2024 Order"). The FERC December 2024 Order addressed the calculation of the contract termination payment for Utility Members served in the Eastern Interconnection and referred to a provision in Tri-State's Amended and Restated Wholesale Power Contract for the Eastern Interconnection with Basin ("Basin Eastern WPC") to inform Tri-State's calculation of such amount. The FERC December 2024 Order also addressed the calculation of a transmission credit for withdrawing Utility Members in the Western Interconnection. On February 12, 2025, Tri-State filed a petition for review of the FERC December 2024 Order, Case No. 25-9522, with the Tenth Circuit Court of Appeals. On April 29, 2025, FERC issued a substantive order on rehearing ("FERC April 2025 Order") addressing requests for hearing and clarification of the FERC December 2024 Order. The FERC April 2025 Order clarified certain aspects of the calculation of the transmission credit for withdrawing Utility Members in the Western Interconnection including that debt associated with distribution facilities should be used in calculating the transmission-related debt. On May 14, 2025, Tri-State filed a petition for review of the FERC April 2025 Order, Case No. 25-9544, with the Tenth Circuit Court of Appeals, which is procedurally consolidated with Case No. 25-9522. On March 24, 2026, the Tenth Circuit Court of Appeals issued an order denying Tri-State's petitions for review and affirming the transmission crediting mechanism. In 2025, Tri-State filed four revisions to Rate Schedule No. 281 as compliance filings with FERC as directed by applicable FERC orders. On August 4, 2025, FERC issued an order on certain of Tri-State's 2025 revisions of Rate Schedule No. 281, subject to further compliance filing ("FERC August 2025 Order"). The FERC August 2025 Order further clarified certain aspects of the calculation of the transmission credit for withdrawing Utility Members in the Western Interconnection including that an allocated amount of Other Non-Current Liabilities and Deferred Credits should be included in the calculation. Tri-State filed a request for rehearing with FERC of the FERC August 2025 Order that was denied by operation of law. On October 28, 2025, Tri-State filed a petition for review of the FERC August 2025 Order, Case No. 25-9583, with the Tenth Circuit Court of Appeals. On November 25, 2025, FERC issued a substantive order on rehearing, which modified the discussion in, but sustained the results of, the FERC August 2025 Order (“FERC November 2025 Order”). On December 9, 2025, Tri-State filed a petition for review of the FERC November 2025 Order, Case No. 25-9594, with the Tenth Circuit Court of Appeals, which is procedurally consolidated with Case No. 25-9583, and is held in abeyance pending final decision of Case Nos. 24-9516, 24-9538, 25-9522, 25-9544. On November 25, 2025, FERC issued an order accepting Tri-State's August and September 2025 revisions of Rate Schedule No. 281. There are no additional compliance filing required for Rate Schedule No. 281. On May 1, 2024, United Power withdrew its membership in Tri-State and pursuant to Rate Schedule No. 281 on file with FERC and a Membership Withdrawal Agreement terminated its wholesale electric service contract. United Power’s contract termination payment amount was $709.4 million. On February 1, 2025, Mountain Parks Electric, Inc. ("MPEI") withdrew its membership in Tri-State and pursuant to Rate Schedule No. 281 on file with FERC and a Membership Withdrawal Agreement terminated its wholesale electric service contract. MPEI's contract termination payment amount was $86 million. On April 1, 2026, LPEA withdrew from membership in Tri-State and pursuant to Rate Schedule No. 281 terminated its wholesale electric service contract with Tri-State. LPEA's contract termination payment amount was $208 million. As provided in the Membership Withdrawal Agreements with United Power, MPEI and LPEA, United Power's, MPEI's, and LPEA's contract termination payments are also subject to true-up in the event Rate Schedule No. 281 and the amount paid are modified pursuant to a subsequent final and non-appealable FERC order, including resolution of the petitions for review. It is not expected that Tri-State will be required to refund any amounts to United Power, MPEI, or LPEA. NRPPD Section 206 Complaint: On March 25, 2024, Northwest Rural Public Power District ("NRPPD") filed an FPA section 206 proceeding with FERC, Docket No. EL24-93, against Tri-State and Basin seeking FERC to exercise primary jurisdiction over the interpretation of the FERC December 2023 Order and the Basin Eastern WPC. In particular, NRPPD requested that FERC hold that NRPPD’s withdrawal from Tri-State is permissible under the Basin Eastern WPC and that NRPPD’s contract termination payment calculation is the appropriate contract termination payment. On December 5, 2024, FERC issued an order denying NRPPD's complaint because NRPPD failed to satisfy its burden under FPA section 206. FERC's order also determined that NRPPD's withdrawal from Tri-State does not cause a breach of the Basin Eastern WPC ("FERC NRPPD Order"). On January 3, 2025, Basin filed a request for rehearing with FERC of the FERC NRPPD Order related to FERC's interpretation of the Basin Eastern WPC that NRPPD's withdrawal from Tri-State is not a breach of the Basin Eastern WPC. On February 3, 2025, FERC issued a notice stating the request for rehearing was denied by operation of law. On February 13, 2025, Basin filed a petition for review of the FERC NRPPD Order, Case No. 25-1060, with the United States Court of Appeals for the District of Columbia Circuit ("DC Circuit Court of Appeals"). On March 17, 2025, Tri-State filed a notice of intervention in Basin's petition for review. On April 29, 2025, FERC issued a substantive order on rehearing addressing the complaint filed by NRPPD. The hearing order modified the discussion in, but sustained the results of, the FERC NRPPD Order. On May 19, 2025, Basin filed a petition for review of FERC’s April 29, 2025, substantive order on rehearing with the DC Circuit Court of Appeals. FERC has moved to dismiss the petition arguing that Basin has no injury as NRPPD’s complaint was dismissed. Oral argument occurred on April 20, 2026. It is not possible to predict the outcome of this matter. NRPPD v. Basin and Tri-State: On July 16, 2025, Basin made multiple filings with FERC stating that Basin is no longer a public utility under Part II of the FPA because it received funding from the United States Department of Agriculture's Rural Utilities Service under the Rural Electrification Act. Basin sought cancellation of the rate schedule filed with FERC concerning the Basin Eastern WPC, which FERC accepted. On July 18, 2025, NRPPD filed a complaint against Basin and Tri-State in the United States District Court, District of Nebraska, 4:25-cv-03153, seeking a declaratory judgment that the FERC NRPPD Order continues to bind Basin and Tri-State under the doctrines of res judicata and collateral estoppel despite Basin’s assertion it is not a public utility under Part II of the FPA. On September 10, 2025, NRPPD filed an amended complaint adding additional claims against Basin. Tri-State and Basin each filed motions to dismiss the amended complaint. It is not possible to predict the outcome of this matter. Las Tusas Fire. In the first quarter of 2026, Tri-State was added as a co-defendant to an existing lawsuit against its Utility Member, Mora San Miguel Electric Cooperative, Inc. (“MSMEC”), relating to the Las Tusas fire that occurred in May 2023 in San Miguel County, New Mexico. Tri-State’s operations, assets or personnel are not implicated in the allegations. Rather, it is alleges that MSMEC’s facilities started the fire and that Tri-State had influence over or oversight of MSMEC’s activities. Tri-State's answer to the amended complaint is due May 20, 2026. Tri-State plans a vigorous defense in close coordination with its insurance carrier and with primary defense costs covered by insurance. It is not possible to predict the outcome of this matter or whether Tri-State will incur any liability in connection with this matter. Energy Sales - Soft-Cap. In 2020, Tri-State made certain energy sales to third parties in excess of the soft-cap price for short-term, spot market sales of $1,000 per megawatt hour established by the Western Electricity Coordinating Council and filed a report with FERC justifying the sales above the soft-cap, EL21-65-000. Based upon the FERC's May 20, 2022 order, in 2022, Tri-State recognized approximately $2.9 million in excess of the soft-cap and refunded $0.4 million to a third party. On July 22, 2022, the California Public Utilities Commission filed a petition for review with the DC Circuit Court of Appeals of FERC’s May 20, 2022 order, 22-1169. Tri-State intervened in this proceeding. In 2023, DC Circuit Court of Appeals consolidate this proceeding with other related proceedings with the DC Circuit Court of Appeals. On July 9, 2024, the DC Circuit Court of Appeals issued an order vacating FERC's order and remanding the case back to FERC to conduct a Mobile-Sierra analysis. On April 16, 2026, FERC issued an order after the DC Circuit Court of Appeals remand and conducted Mobile-Sierra analysis. FERC determined that no refunds are required by Tri-State and that Tri-State is entitled to recoup previous refunds to third parties.

Other than as disclosed below or in Tri-State's annual report on Form 10-K for the year ended December 31, 2025 filed with the SEC, Tri-State does not expect any litigation or proceeding pending or threatened against it to have a potential material effect on its financial condition, results of operations or cash flows.

CTP Proceeding: Pursuant to Tri-State's Bylaws, a Member may only withdraw from membership in Tri-State upon compliance with such equitable terms and conditions as Tri-State's Board may prescribe, provided, however, that no Member shall be permitted to withdraw until it has met all its contractual obligations to Tri-State. On September 1, 2021, Tri-State filed with FERC a contract termination payment methodology tariff as Rate Schedule No. 281 that provides a process should a Utility Member elect to withdraw from membership in Tri-State and terminate its wholesale electric service contract, Docket No. ER21-2818. The tariff process includes requirements for a two-year notice and the payment to Tri-State of a contract termination payment. On October 29, 2021, FERC accepted Rate Schedule No. 281, effective November 1, 2021, subject to refund. FERC set the matter for hearing and instituted a concurrent Federal Power Act ("FPA") section 206 proceeding to determine the justness and reasonableness of the methodology. On December 19, 2023, FERC issued an order adopting a modified balance sheet approach for the contract termination payment methodology ("FERC December 2023 Order").

On March 28, 2024, Tri-State filed a petition for review of the FERC December 2023 Order with the United States Court of Appeals for the Tenth Circuit ("Tenth Circuit Court of Appeals"), Case No. 24-9516, related to FERC's rejection of the lost revenue approach and also other items. On May 23, 2024, FERC issued a substantive order on rehearing, which modified the discussion in, but sustained the results of, the FERC December 2023 Order (“FERC May 2024 Order”). On May 31, 2024, Tri-State filed a petition for review of the FERC May 2024 Order, Case No. 24-9538, with the Tenth Circuit Court of Appeals. On June 3, 2024, the Tenth Circuit Court of Appeals issued an order partially consolidating the cases for purposes of briefing. On March 24, 2026, the Tenth Circuit Court of Appeals issued an opinion denying Tri-State's petitions for review and affirming

In 2024, Tri-State filed three revisions to Rate Schedule No. 281 as compliance filings with FERC as directed by applicable FERC orders. On December 5, 2024, FERC issued an order on certain of Tri-State's 2024 revisions of Rate Schedule No. 281, subject to further compliance filing ("FERC December 2024 Order"). The FERC December 2024 Order addressed the calculation of the contract termination payment for Utility Members served in the Eastern Interconnection and referred to a provision in Tri-State's Amended and Restated Wholesale Power Contract for the Eastern Interconnection with Basin ("Basin Eastern WPC") to inform Tri-State's calculation of such amount. The FERC December 2024 Order also addressed the calculation of a transmission credit for withdrawing Utility Members in the Western Interconnection.

On February 12, 2025, Tri-State filed a petition for review of the FERC December 2024 Order, Case No. 25-9522, with the Tenth Circuit Court of Appeals. On April 29, 2025, FERC issued a substantive order on rehearing ("FERC April 2025 Order") addressing requests for hearing and clarification of the FERC December 2024 Order. The FERC April 2025 Order clarified certain aspects of the calculation of the transmission credit for withdrawing Utility Members in the Western Interconnection including that debt associated with distribution facilities should be used in calculating the transmission-related debt. On May 14, 2025, Tri-State filed a petition for review of the FERC April 2025 Order, Case No. 25-9544, with the Tenth Circuit Court of Appeals, which is procedurally consolidated with Case No. 25-9522. On March 24, 2026, the Tenth Circuit Court of Appeals issued an order denying Tri-State's petitions for review and affirming the transmission crediting mechanism.

In 2025, Tri-State filed four revisions to Rate Schedule No. 281 as compliance filings with FERC as directed by applicable FERC orders. On August 4, 2025, FERC issued an order on certain of Tri-State's 2025 revisions of Rate Schedule No. 281, subject to further compliance filing ("FERC August 2025 Order"). The FERC August 2025 Order further clarified certain aspects of the calculation of the transmission credit for withdrawing Utility Members in the Western Interconnection including that an allocated amount of Other Non-Current Liabilities and Deferred Credits should be included in the calculation. Tri-State filed a request for rehearing with FERC of the FERC August 2025 Order that was denied by operation of law. On October 28, 2025, Tri-State filed a petition for review of the FERC August 2025 Order, Case No. 25-9583, with the Tenth Circuit Court of Appeals. On November 25, 2025, FERC issued a substantive order on rehearing, which modified the discussion in, but sustained the results of, the FERC August 2025 Order (“FERC November 2025 Order”). On December 9, 2025, Tri-State filed a petition for review of the FERC November 2025 Order, Case No. 25-9594, with the Tenth Circuit Court of Appeals, which is procedurally consolidated with Case No. 25-9583, and is held in abeyance pending final decision of Case Nos. 24-9516, 24-9538, 25-9522, 25-9544.

On May 1, 2024, United Power withdrew its membership in Tri-State and pursuant to Rate Schedule No. 281 on file with FERC and a Membership Withdrawal Agreement terminated its wholesale electric service contract. United Power’s contract termination payment amount was $709.4 million. On February 1, 2025, Mountain Parks Electric, Inc. ("MPEI") withdrew its membership in Tri-State and pursuant to Rate Schedule No. 281 on file with FERC and a Membership Withdrawal Agreement terminated its wholesale electric service contract. MPEI's contract termination payment amount was $86 million. On April 1, 2026, LPEA withdrew from membership in Tri-State and pursuant to Rate Schedule No. 281 terminated its wholesale electric service contract with Tri-State. LPEA's contract termination payment amount was $208 million.

As provided in the Membership Withdrawal Agreements with United Power, MPEI and LPEA, United Power's, MPEI's, and LPEA's contract termination payments are also subject to true-up in the event Rate Schedule No. 281 and the amount paid are modified pursuant to a subsequent final and non-appealable FERC order, including resolution of the petitions for review. It is not expected that Tri-State will be required to refund any amounts to United Power, MPEI, or LPEA.

NRPPD Section 206 Complaint: On March 25, 2024, Northwest Rural Public Power District ("NRPPD") filed an FPA section 206 proceeding with FERC, Docket No. EL24-93, against Tri-State and Basin seeking FERC to exercise primary jurisdiction over the interpretation of the FERC December 2023 Order and the Basin Eastern WPC. In particular, NRPPD requested that FERC hold that NRPPD’s withdrawal from Tri-State is permissible under the Basin Eastern WPC and that NRPPD’s contract termination payment calculation is the appropriate contract termination payment. On December 5, 2024, FERC issued an order denying NRPPD's complaint because NRPPD failed to satisfy its burden under FPA section 206. FERC's order also determined that NRPPD's withdrawal from Tri-State does not cause a breach of the Basin Eastern WPC ("FERC NRPPD Order"). On January 3, 2025, Basin filed a request for rehearing with FERC of the FERC NRPPD Order related to FERC's interpretation of the Basin Eastern WPC that NRPPD's withdrawal from Tri-State is not a breach of the Basin Eastern WPC. On February 3, 2025, FERC issued a notice stating the request for rehearing was denied by operation of law. On February 13, 2025, Basin filed a petition for review of the FERC NRPPD Order, Case No. 25-1060, with the United States

On April 29, 2025, FERC issued a substantive order on rehearing addressing the complaint filed by NRPPD. The hearing order modified the discussion in, but sustained the results of, the FERC NRPPD Order. On May 19, 2025, Basin filed a petition for review of FERC’s April 29, 2025, substantive order on rehearing with the DC Circuit Court of Appeals. FERC has moved to dismiss the petition arguing that Basin has no injury as NRPPD’s complaint was dismissed. Oral argument occurred on April 20, 2026. It is not possible to predict the outcome of this matter.

NRPPD v. Basin and Tri-State: On July 16, 2025, Basin made multiple filings with FERC stating that Basin is no longer a public utility under Part II of the FPA because it received funding from the United States Department of Agriculture's Rural Utilities Service under the Rural Electrification Act. Basin sought cancellation of the rate schedule filed with FERC concerning the Basin Eastern WPC, which FERC accepted. On July 18, 2025, NRPPD filed a complaint against Basin and Tri-State in the United States District Court, District of Nebraska, 4:25-cv-03153, seeking a declaratory judgment that the FERC NRPPD Order continues to bind Basin and Tri-State under the doctrines of res judicata and collateral estoppel despite Basin’s assertion it is not a public utility under Part II of the FPA. On September 10, 2025, NRPPD filed an amended complaint adding additional claims against Basin. Tri-State and Basin each filed motions to dismiss the amended complaint. It is not possible to predict the outcome of this matter.

Las Tusas Fire. In the first quarter of 2026, Tri-State was added as a co-defendant to an existing lawsuit against its Utility Member, Mora San Miguel Electric Cooperative, Inc. (“MSMEC”), relating to the Las Tusas fire that occurred in May 2023 in San Miguel County, New Mexico. Tri-State’s operations, assets or personnel are not implicated in the allegations. Rather, it is alleges that MSMEC’s facilities started the fire and that Tri-State had influence over or oversight of MSMEC’s activities. Tri-State's answer to the amended complaint is due May 20, 2026. Tri-State plans a vigorous defense in close coordination with its insurance carrier and with primary defense costs covered by insurance. It is not possible to predict the outcome of this matter or whether Tri-State will incur any liability in connection with this matter.