COMMITMENTS AND CONTINGENCIES	3 Months Ended
Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES COMMITMENTS There have been no significant changes to TEP's long-term commitments since December 31, 2025, except as noted below. Purchase Commitments Renewable Power Purchase Agreements In March 2026, a renewable PPA facility with 160 MW of solar capacity was placed in service. On April 3, 2026, an additional facility with 100 MW of solar capacity and 100 MW of battery storage (400 MWh of energy capacity) was placed in service. CONTINGENCIES Legal Matters TEP is involved in various legal proceedings that arise in the ordinary course of business. These matters include, from time to time, claims for punitive or exemplary damages. Based on currently available information, TEP does not believe that the outcome of these proceedings will have a material adverse effect on TEP's financial position, results of operations, or cash flows. Mine Reclamation at Generation Facilities Not Operated by TEP TEP pays ongoing mine reclamation costs for coal mines that supply generation facilities where TEP holds an ownership interest but is not the operator. The estimated liability for final mine reclamation depends on assumptions, such as projected costs, timing, and inflation. When these assumptions change, TEP adjusts future expense recognition over the remaining term of the applicable coal supply agreement. TEP’s PPFAC allows the pass-through of final mine reclamation costs to retail customers as part of fuel costs. Therefore, TEP defers these expenses by recording a regulatory asset and a reclamation liability over the remaining life of the respective coal supply agreement. TEP recovers the regulatory asset through the PPFAC as final mine reclamation costs are funded. After expiration of the related coal supply agreement, any changes in the estimated liability are recorded to both the regulatory asset and reclamation liability. TEP is responsible for a portion of final mine reclamation costs for the mines at Four Corners and San Juan. TEP’s liability related to Four Corners totaled $2 million and $3 million as of March 31, 2026, and December 31, 2025, respectively, and was recorded in Current Liabilities—Other and Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. TEP's Four Corners coal supply agreement expires in 2031. TEP ceased operations at San Juan in 2022 following expiration of its coal supply agreement. TEP’s remaining final mine reclamation liability at San Juan was $21 million and $23 million as of March 31, 2026, and December 31, 2025, respectively, and was recorded in Current Liabilities—Other and Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. TEP established a trust to fund its share of estimated final mine reclamation costs at San Juan that will remain in effect until reclamation activities are completed, which are currently projected to be completed in 2040. See Note 1 for additional information on restricted cash related to reclamation and decommissioning costs at San Juan. Performance Guarantees TEP participates in joint generation agreements at Four Corners and Luna, which expire in 2041 and 2046, respectively. Under these agreements, all participants, including TEP, guarantee certain performance obligations. If a participant defaults on payment, the non-defaulting participants must cover a proportionate share of expenses otherwise payable by the defaulting participant. In return, the non-defaulting participants are entitled to receive a proportionate share of the defaulting participant's generation capacity. For Luna, there is no maximum potential payment under this guarantee. For Four Corners, the maximum potential payment for non-defaulting participants is $250 million. As of March 31, 2026, no payment defaults have occurred under either agreement. The Navajo and San Juan participation agreements expired in 2019 and 2022, respectively, but certain performance obligations continue through the decommissioning of both generation facilities. In the case of a default on these continuing obligations, the non-defaulting participants are entitled to seek financial recovery directly from the defaulting party. Environmental Matters TEP operates under federal, state, and local environmental laws and regulations covering air and water quality, renewable portfolio standards, emissions performance, climate change, coal combustion byproduct disposal, hazardous and solid waste disposal, protected species, and other environmental matters that have the potential to impact TEP's current and future operations. These requirements are subject to interpretation and may be clarified by court decisions. Because these laws and regulations continue to evolve, TEP is unable to predict the impact of the changing laws and regulations on its operations or consolidated financial results. TEP expects to recover environmental compliance costs through customer rates. TEP believes it is in material compliance with applicable environmental laws and regulations.

In March 2026, a renewable PPA facility with 160 MW of solar capacity was placed in service. On April 3, 2026, an additional facility with 100 MW of solar capacity and 100 MW of battery storage (400 MWh of energy capacity) was placed in service.

TEP is involved in various legal proceedings that arise in the ordinary course of business. These matters include, from time to time, claims for punitive or exemplary damages. Based on currently available information, TEP does not believe that the outcome of these proceedings will have a material adverse effect on TEP's financial position, results of operations, or cash flows.

TEP pays ongoing mine reclamation costs for coal mines that supply generation facilities where TEP holds an ownership interest but is not the operator. The estimated liability for final mine reclamation depends on assumptions, such as projected costs, timing, and inflation. When these assumptions change, TEP adjusts future expense recognition over the remaining term of the applicable coal supply agreement. TEP’s PPFAC allows the pass-through of final mine reclamation costs to retail customers as part of fuel costs. Therefore, TEP defers these expenses by recording a regulatory asset and a reclamation liability over the remaining life of the respective coal supply agreement. TEP recovers the regulatory asset through the PPFAC as final mine reclamation costs are funded. After expiration of the related coal supply agreement, any changes in the estimated liability are recorded to both the regulatory asset and reclamation liability.

TEP is responsible for a portion of final mine reclamation costs for the mines at Four Corners and San Juan. TEP’s liability related to Four Corners totaled $2 million and $3 million as of March 31, 2026, and December 31, 2025, respectively, and was recorded in Current Liabilities—Other and Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. TEP's Four Corners coal supply agreement expires in 2031.

TEP ceased operations at San Juan in 2022 following expiration of its coal supply agreement. TEP’s remaining final mine reclamation liability at San Juan was $21 million and $23 million as of March 31, 2026, and December 31, 2025, respectively, and was recorded in Current Liabilities—Other and Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets. TEP established a trust to fund its share of estimated final mine reclamation costs at San Juan that will remain in effect until reclamation activities are completed, which are currently projected to be completed in 2040. See Note 1 for additional information on restricted cash related to reclamation and decommissioning costs at San Juan.

TEP participates in joint generation agreements at Four Corners and Luna, which expire in 2041 and 2046, respectively. Under these agreements, all participants, including TEP, guarantee certain performance obligations. If a participant defaults on payment, the non-defaulting participants must cover a proportionate share of expenses otherwise payable by the defaulting participant. In return, the non-defaulting participants are entitled to receive a proportionate share of the defaulting participant's generation capacity. For Luna, there is no maximum potential payment under this guarantee. For Four Corners, the maximum potential payment for non-defaulting participants is $250 million. As of March 31, 2026, no payment defaults have occurred under either agreement.

The Navajo and San Juan participation agreements expired in 2019 and 2022, respectively, but certain performance obligations continue through the decommissioning of both generation facilities. In the case of a default on these continuing obligations, the non-defaulting participants are entitled to seek financial recovery directly from the defaulting party.

TEP operates under federal, state, and local environmental laws and regulations covering air and water quality, renewable portfolio standards, emissions performance, climate change, coal combustion byproduct disposal, hazardous and solid waste disposal, protected species, and other environmental matters that have the potential to impact TEP's current and future operations. These requirements are subject to interpretation and may be clarified by court decisions. Because these laws and regulations continue to evolve, TEP is unable to predict the impact of the changing laws and regulations on its operations or consolidated financial results. TEP expects to recover environmental compliance costs through customer rates. TEP believes it is in material compliance with applicable environmental laws and regulations.