Commitments and Contingencies	3 Months Ended
Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Environmental DTE Electric Air — DTE Electric is subject to the EPA ozone and fine particulate transport and acid rain regulations that limit power plant emissions of SO2 and NOX. The EPA and the state of Michigan have also issued emission reduction regulations relating to ozone, fine particulate, regional haze, mercury, and other air pollution. These rules have led to controls on fossil-fueled power plants to reduce SO2, NOX, mercury, and other emissions. Additional rule making may occur over the next few years which could require additional controls for SO2, NOX, and other hazardous air pollutants. In 2015, the EPA finalized the NAAQS for ground level ozone. In August 2018, the EPA designated southeast Michigan as "marginal non-attainment" with the 2015 ozone NAAQS. In January 2022, after collecting several years of data, the state submitted a request to the EPA for redesignation of the southeast Michigan ozone non-attainment area to attainment, and to accept their maintenance plan and emission inventories as a revision to the Michigan SIP. On May 19, 2023, the EPA posted in the Federal Register the redesignation of attainment of the ozone standard for the seven-county Southeast Michigan region. DTE Electric does not expect a significant financial impact related to the ozone NAAQS at this time, pending finalization of the state rules and implementation plans. In March 2024, the EPA finalized the NAAQS for fine particulate matter, particles of pollution with diameters generally 2.5 micrometers and smaller (PM2.5). It is likely that areas of Michigan in which DTE Electric operates will be designated as non-attainment in the future and the state will be required to develop a SIP for such areas. No impact is expected in the near term, and any long-term financial impacts cannot be assessed at this time. In May 2023, the EPA proposed new rules to address emissions of GHGs from existing, new, modified, or reconstructed sources in the power sector. DTE Electric provided individual comments on the proposal and also worked with industry partners on a broader set of comments. The financial impact cannot be estimated until a final rule is issued, which is currently expected by May 2024. Pending or future legislation or other regulatory actions could have a material impact on DTE Electric's operations and financial position and the rates charged to its customers. Potential impacts include expenditures for environmental equipment beyond what is currently planned, financing costs related to additional capital expenditures, the purchase of emission credits from market sources, higher costs of purchased power, and the retirement of facilities where control equipment is not economical. DTE Electric would seek to recover these incremental costs through increased rates charged to its utility customers, as authorized by the MPSC. To comply with air pollution requirements, DTE Electric has spent approximately $2.4 billion. DTE Electric does not anticipate additional capital expenditures for air pollution requirements, subject to the results of future rulemakings. Water — In response to EPA regulations and in accordance with the Clean Water Act section 316(b), DTE Electric was required to examine alternatives for reducing the environmental impacts of the cooling water intake structures at several of its facilities. A final rule became effective in October 2014, which required studies to be completed and submitted as part of the NPDES permit application process to determine the type of technology needed to reduce impacts to fish. DTE Electric has completed the required studies and submitted reports for most of its generation plants, and a final study is in-process for Monroe power plant. Final compliance for the installation of any required technology to reduce the impacts of water intake structures will be determined by the state on a case by case, site specific basis. DTE Electric is currently evaluating the compliance options and working with the state of Michigan on identifying any necessary controls or modifications to existing intake structures. DTE Electric's current capital plan includes an estimated $81 million of compliance-related expenditures, including $54 million for 2024 through 2028. Projected capital expenditures are expected to decrease as a result of the planned conversion of the Belle River power plant to natural gas and the retirement of Monroe power plant generating units. However, discussions with the state are ongoing and a revised cost estimate has not yet been determined. As part of the Monroe power plant NPDES permit, EGLE has added requirements to evaluate the thermal discharge of the facility as it relates to Clean Water Act section 316(a) regulations. DTE Electric has submitted to EGLE a biological demonstration study plan to evaluate the thermal discharge impacts to an aquatic community. After approval of the plan by EGLE and completion of field sampling, data will be processed and compiled into a comprehensive report. At the present time, DTE Electric cannot predict the outcome of this evaluation or financial impact. Contaminated and Other Sites — Prior to the construction of major interstate natural gas pipelines, gas for heating and other uses was manufactured locally from processes involving coal, coke, or oil. The facilities, which produced gas, have been designated as MGP sites. DTE Electric conducted remedial investigations at contaminated sites, including three former MGP sites. Cleanup of one of the MGP sites is complete, and that site is closed. The investigations have revealed contamination related to the by-products of gas manufacturing at each MGP site. In addition to the MGP sites, DTE Electric is also in the process of cleaning up other contaminated sites, including the area surrounding an ash landfill, electrical distribution substations, electric generating power plants, and underground and above ground storage tank locations. The findings of these investigations indicated that the estimated cost to remediate these sites is expected to be incurred over the next several years. At March 31, 2024 and December 31, 2023, DTE Electric had $9 million accrued for remediation. These costs are not discounted to their present value. Any change in assumptions, such as remediation techniques, nature and extent of contamination, and regulatory requirements, could impact the estimate of remedial action costs for the sites and affect DTE Electric’s financial position and cash flows. DTE Electric believes the likelihood of a material change to the accrued amount is remote based on current knowledge of the conditions at each site. Coal Combustion Residuals and Effluent Limitations Guidelines — A final EPA rule for the disposal of coal combustion residuals, commonly known as coal ash, became effective in October 2015 and has continued to be updated in subsequent years. The rule is based on the continued listing of coal ash as a non-hazardous waste and relies on various self-implementation design and performance standards. DTE Electric owns and operates three permitted engineered coal ash storage facilities to dispose of coal ash from coal-fired power plants and operates a number of smaller impoundments at its power plants subject to certain provisions in the CCR rule. At certain facilities, the rule required ongoing sampling and testing of monitoring wells, compliance with groundwater standards, and the closure of basins at the end of the useful life of the associated power plant. On August 28, 2020, Part A of the CCR rule was published in the Federal Register and required all unlined impoundments to initiate closure as soon as technically feasible, but no later than April 11, 2021. Additionally, the rule amends certain reporting requirements and CCR website requirements. On November 12, 2020, Part B of the CCR Rule was published in the Federal Register and provides a process to determine if certain unlined impoundments with an alternative liner system may be sufficiently protective and therefore may continue to operate. DTE Electric submitted applications to the EPA that support continued use of all impoundments through their active lives. DTE Electric subsequently ceased receipt of waste at the St. Clair power plant bottom ash basins and initiated closure, resulting in withdrawal of the Part A demonstration for the plant. Additionally, DTE Electric implemented projects at the Belle River and Monroe power plants to cease receipt of waste within any unlined CCR impoundments, resulting in withdrawals of the Part B applications for those plants. On May 18, 2023, the EPA posted in the Federal Register a proposed rule to regulate legacy CCR surface impoundments and CCR management units. The rule proposes to expand the reach of the CCR rule to inactive electric generation sites and previously unregulated locations of CCR at a regulated facility. DTE Electric is currently evaluating the proposed rule. The financial impact of the proposed rule cannot be estimated until a final rule is issued, which is currently expected in mid-2024. At the state level, legislation was signed in December 2018 and provides for further regulation of the CCR program in Michigan. Additionally, the statutory revision provides the basis of a CCR program that EGLE has submitted to the EPA for approval to fully regulate the CCR program in Michigan in lieu of a federal permit program. The EPA is currently working with EGLE in reviewing the submitted state program, and DTE Electric will work with EGLE to implement the state program that may be approved in the future. On October 13, 2020, the EPA finalized the ELG Reconsideration Rule which revised the regulations from the 2015 ELG rule for FGD wastewater and bottom ash transport water only. The Reconsideration Rule re-established the technology-based effluent limitations guidelines and standards applicable to FGD wastewater and bottom ash transport water. The EPA set the applicability dates for bottom ash transport water "as soon as possible" beginning October 13, 2021 and no later than December 31, 2025. FGD wastewater retrofits must be completed "as soon as possible" beginning October 13, 2021 and no later than December 31, 2025 or December 31, 2028 if a permittee decides to pursue the Voluntary Incentives Program (VIP) subcategory for FGD wastewater. If a facility applies for the VIP, they must meet more stringent standards, but are allowed an extended time period to meet the compliance requirements. The Reconsideration Rule also provides additional compliance opportunities by finalizing low utilization and cessation of coal burning subcategories. The Reconsideration Rule provides new opportunities for DTE Electric to evaluate existing ELG compliance strategies and make any necessary adjustments to ensure full compliance with the ELGs in a cost-effective manner. Compliance schedules for individual facilities and individual waste streams are determined through issuance of new NPDES permits by the state of Michigan. The state of Michigan has issued an NPDES permit for the Belle River power plant establishing compliance deadlines based on the 2020 Reconsideration Rule. On October 11, 2021, in consideration of the deadlines above, DTE Electric submitted a Notice of Planned Participation ("NOPP") to the state of Michigan that formally announced the intent to pursue compliance subcategories as ELG compliance options: the cessation of coal at the Belle River power plant no later than December 31, 2028 and the VIP for FGD wastewater at Monroe power plant by December 31, 2028. On March 29, 2023, the EPA published two draft proposals to revise existing ELG rules. The first draft proposal reopened the cessation of coal compliance subcategory from the 2020 ELG rule and allows for compliance by committing to such cessation no later than December 31, 2028. This proposal was finalized by the EPA on May 30, 2023. The second draft proposal is a broader update to the ELG rules that includes revised compliance standards for FGD wastewater, bottom ash transport water, and other wastewater streams with a compliance date no later than December 31, 2029. DTE Electric's compliance strategy includes the conversion of the two generating units at the Belle River power plant to a natural gas peaking resource in 2025-2026, which was included in the NOPP filed in 2021. DTE Electric also submitted a new NOPP to apply for the cessation of coal compliance subcategory for generating units 3 and 4 at the Monroe power plant. DTE Electric plans to retire Monroe's generating units 1 and 2 in 2032. DTE Electric continues to evaluate compliance strategies, technologies and system designs to achieve compliance with the EPA rules at the Monroe power plant. DTE Electric currently estimates the impact of the CCR and ELG rules to be $412 million of capital expenditures, including $403 million for 2024 through 2028. This estimate may change in future periods as DTE Electric evaluates the CCR and ELG rules discussed above that are expected to be finalized in mid-2024. DTE Gas Contaminated and Other Sites — DTE Gas owns or previously owned 14 former MGP sites. Investigations have revealed contamination related to the by-products of gas manufacturing at each site. Cleanup of eight MGP sites is complete and those sites are closed. DTE Gas has also completed partial closure of four additional sites. Cleanup activities associated with the remaining sites will continue over the next several years. The MPSC has established a cost deferral and rate recovery mechanism for investigation and remediation costs incurred at former MGP sites. In addition to the MGP sites, DTE Gas is also in the process of cleaning up other contaminated sites, including gate stations, gas pipeline releases, and underground storage tank locations. As of March 31, 2024 and December 31, 2023, DTE Gas had $26 million accrued for remediation. These costs are not discounted to their present value. Any change in assumptions, such as remediation techniques, nature and extent of contamination, and regulatory requirements, could impact the estimate of remedial action costs for the sites and affect DTE Gas' financial position and cash flows. DTE Gas anticipates the cost amortization methodology approved by the MPSC, which allows for amortization of the MGP costs over a ten-year period beginning with the year subsequent to the year the MGP costs were incurred, will prevent the associated investigation and remediation costs from having a material adverse impact on DTE Gas' results of operations. Air — In March 2023, the EPA published the Good Neighbor Rule, which includes provisions for compressor engines operated for the transportation of natural gas. The status of the rule remains uncertain as litigation is ongoing. At this time, DTE Gas does not expect a significant financial impact. As noted above for DTE Electric, the EPA finalized the NAAQS for fine particulate matter in March 2024. It is likely that areas of Michigan in which DTE Gas operates will be designated as non-attainment in the future and the state will be required to develop a SIP for such areas. No impact is expected in the near term, and any long-term financial impacts cannot be assessed at this time. Non-utility DTE Energy's non-utility businesses are subject to a number of environmental laws and regulations dealing with the protection of the environment from various pollutants. In March 2019, the EPA issued an FOV to EES Coke Battery, LLC ("EES Coke"), the Michigan coke battery facility that is a wholly-owned subsidiary of DTE Energy, alleging that the 2008 and 2014 permits issued by EGLE did not comply with the Clean Air Act. In September 2020, the EPA issued another FOV alleging EES Coke's 2018 and 2019 SO2 emissions exceeded projections and hence violated non-attainment new source review permitting requirements. EES Coke evaluated the EPA's alleged violations and believes that the permits approved by EGLE complied with the Clean Air Act. EES Coke responded to the EPA's September 2020 allegations demonstrating its actual emissions are compliant with non-attainment new source review requirements. On June 1, 2022, the U.S. Department of Justice, on behalf of the EPA, filed a complaint against EES Coke in the U.S. District Court for the Eastern District of Michigan alleging that EES Coke failed to comply with non-attainment new source review requirements under the Clean Air Act when it applied for the 2014 permit. In November 2022, the Sierra Club and City of River Rouge were granted intervention. The case is currently in the discovery phase and trial is scheduled for April 2025. At the present time, DTE Energy cannot predict the outcome or financial impact of this matter. Other In 2010, the EPA finalized a new one-hour SO2 ambient air quality standard that requires states to submit plans and associated timelines for non-attainment areas that demonstrate attainment with the new SO2 standard in phases. Phase 1 addresses non-attainment areas designated based on ambient monitoring data. Phase 2 addresses non-attainment areas with large sources of SO2 and modeled concentrations exceeding the National Ambient Air Quality Standards for SO2. Phase 3 addresses smaller sources of SO2 with modeled or monitored exceedances of the new SO2 standard. Michigan's Phase 1 non-attainment area included DTE Energy facilities. However, the EPA published a Federal Implementation Plan (FIP) for the area in June 2022 that did not impact any DTE Energy facilities. It is also not expected that Phase 3 will have any impact on DTE Energy. Michigan's Phase 2 non-attainment area includes DTE Electric facilities in St. Clair County. The EPA approved a clean data determination request submitted by EGLE. This determination suspends certain planning requirements and sanctions for the non-attainment area for as long as the area continues to attain the 2010 SO2 air quality standards, but this does not automatically redesignate the area to attainment. Until the area is officially redesignated as attainment, DTE Energy is unable to determine the impacts. REF Guarantees DTE Energy provided certain guarantees and indemnities in conjunction with the sales of interests in or lease of its previously operated REF facilities. The guarantees cover potential commercial, environmental, and tax-related obligations that will survive until 90 days after expiration of all applicable statutes of limitations. DTE Energy estimates that its maximum potential liability under these guarantees at March 31, 2024 was $392 million. Payments under these guarantees are considered remote. Other Guarantees In certain limited circumstances, the Registrants enter into contractual guarantees. The Registrants may guarantee another entity’s obligation in the event it fails to perform and may provide guarantees in certain indemnification agreements. The Registrants may also provide indirect guarantees for the indebtedness of others. DTE Energy’s guarantees are not individually material with maximum potential payments totaling $44 million at March 31, 2024. Payments under these guarantees are considered remote. The Registrants are periodically required to obtain performance surety bonds in support of obligations to various governmental entities and other companies in connection with its operations. As of March 31, 2024, DTE Energy had $334 million of performance bonds outstanding, including $159 million for DTE Electric. Performance bonds are not individually material, except for $130 million of bonds supporting Energy Trading operations. These bonds are meant to provide counterparties with additional assurance that Energy Trading will meet its contractual obligations for various commercial transactions. The terms of the bonds align with those of the underlying Energy Trading contracts and are estimated to be outstanding approximately 1 to 3 years. In the event that any performance bonds are called for nonperformance, the Registrants would be obligated to reimburse the issuer of the performance bond. The Registrants are released from the performance bonds as the contractual performance is completed and does not believe that a material amount of any currently outstanding performance bonds will be called. Labor Contracts There are several bargaining units for DTE Energy subsidiaries' approximately 4,900 represented employees, including DTE Electric's approximately 2,550 represented employees. This represents 51% and 59% of DTE Energy's and DTE Electric's total employees, respectively. Of these represented employees, approximately 8% have contracts expiring within one year for DTE Energy. None of the represented employees have contracts expiring within one year for DTE Electric. Purchase Commitments Utility capital expenditures and expenditures for non-utility businesses will be approximately $4.7 billion and $3.4 billion in 2024 for DTE Energy and DTE Electric, respectively. The Registrants have made certain commitments in connection with the estimated 2024 annual capital expenditures. Ludington Plant Contract Dispute DTE Electric and Consumers Energy Company ("Consumers"), joint owners of the Ludington Hydroelectric Pumped Storage plant ("Ludington"), are parties to a 2010 engineering, procurement, and construction agreement with Toshiba America Energy Systems ("TAES"), under which TAES contracted to perform a major overhaul and upgrade of Ludington. The overhauled Ludington units are operational, but TAES' work has been defective and non-conforming. DTE Electric and Consumers have demanded that TAES provide a comprehensive plan to resolve those matters, including adherence to its warranty commitments and other contractual obligations. DTE Electric and Consumers have taken extensive efforts to resolve these issues with TAES, including a formal demand to TAES' parent, Toshiba Corporation, under a parent guaranty it provided. TAES has not provided a comprehensive plan or otherwise met its performance obligations. In order to enforce the contract, DTE Electric and Consumers filed a complaint against TAES and Toshiba Corporation in the U.S. District Court for the Eastern District of Michigan in April 2022. In June 2022, TAES and Toshiba Corporation filed a motion to dismiss the complaint, along with counterclaims seeking approximately $15 million in damages related to payments allegedly owed under the parties' contract. During September 2022, the motion to dismiss the complaint was denied. DTE Electric believes the outstanding counterclaims are without merit, but would be liable for 49% of the damages if approved. In October 2022, the combined parties submitted a joint discovery plan to proceed with the litigation process and a potential trial during the second half of 2024. DTE Electric cannot predict the financial impact or outcome of this matter. In May 2023, the MPSC approved a jointly-filed request by DTE Electric and Consumers for authority to defer as a regulatory asset the costs associated with repairing or replacing the defective work performed by TAES while the litigation with TAES and Toshiba Corporation moves forward. Such costs will be offset by any potential litigation proceeds received from TAES or Toshiba Corporation. DTE Electric and Consumers will have the opportunity to seek recovery and ratemaking treatment for amounts which are not recovered from TAES or Toshiba Corporation. Other Contingencies The Registrants are involved in certain other legal, regulatory, administrative, and environmental proceedings before various courts, arbitration panels, and governmental agencies concerning claims arising in the ordinary course of business. These proceedings include certain contract disputes, additional environmental reviews and investigations, audits, inquiries from various regulators, and pending judicial matters. The Registrants cannot predict the final disposition of such proceedings. The Registrants regularly review legal matters and record provisions for claims that they can estimate and are considered probable of loss. The resolution of these pending proceedings is not expected to have a material effect on the Registrants' Consolidated Financial Statements in the periods they are resolved. For a discussion of contingencies related to regulatory matters and derivatives, see Notes 4 and 7 to the Consolidated Financial Statements, "Regulatory Matters" and "Financial and Other Derivative Instruments," respectively.

Air — DTE Electric is subject to the EPA ozone and fine particulate transport and acid rain regulations that limit power plant emissions of SO2 and NOX. The EPA and the state of Michigan have also issued emission reduction regulations relating to ozone, fine particulate, regional haze, mercury, and other air pollution. These rules have led to controls on fossil-fueled power plants to reduce SO2, NOX, mercury, and other emissions. Additional rule making may occur over the next few years which could require additional controls for SO2, NOX, and other hazardous air pollutants.

In 2015, the EPA finalized the NAAQS for ground level ozone. In August 2018, the EPA designated southeast Michigan as "marginal non-attainment" with the 2015 ozone NAAQS. In January 2022, after collecting several years of data, the state submitted a request to the EPA for redesignation of the southeast Michigan ozone non-attainment area to attainment, and to accept their maintenance plan and emission inventories as a revision to the Michigan SIP. On May 19, 2023, the EPA posted in the Federal Register the redesignation of attainment of the ozone standard for the seven-county Southeast Michigan region. DTE Electric does not expect a significant financial impact related to the ozone NAAQS at this time, pending finalization of the state rules and implementation plans.

In March 2024, the EPA finalized the NAAQS for fine particulate matter, particles of pollution with diameters generally 2.5 micrometers and smaller (PM2.5). It is likely that areas of Michigan in which DTE Electric operates will be designated as non-attainment in the future and the state will be required to develop a SIP for such areas. No impact is expected in the near term, and any long-term financial impacts cannot be assessed at this time.

In May 2023, the EPA proposed new rules to address emissions of GHGs from existing, new, modified, or reconstructed sources in the power sector. DTE Electric provided individual comments on the proposal and also worked with industry partners on a broader set of comments. The financial impact cannot be estimated until a final rule is issued, which is currently expected by May 2024.

Pending or future legislation or other regulatory actions could have a material impact on DTE Electric's operations and financial position and the rates charged to its customers. Potential impacts include expenditures for environmental equipment beyond what is currently planned, financing costs related to additional capital expenditures, the purchase of emission credits from market sources, higher costs of purchased power, and the retirement of facilities where control equipment is not economical. DTE Electric would seek to recover these incremental costs through increased rates charged to its utility customers, as authorized by the MPSC.

Water — In response to EPA regulations and in accordance with the Clean Water Act section 316(b), DTE Electric was required to examine alternatives for reducing the environmental impacts of the cooling water intake structures at several of its facilities. A final rule became effective in October 2014, which required studies to be completed and submitted as part of the NPDES permit application process to determine the type of technology needed to reduce impacts to fish. DTE Electric has completed the required studies and submitted reports for most of its generation plants, and a final study is in-process for Monroe power plant. Final compliance for the installation of any required technology to reduce the impacts of water intake structures will be determined by the state on a case by case, site specific basis.

DTE Electric is currently evaluating the compliance options and working with the state of Michigan on identifying any necessary controls or modifications to existing intake structures. DTE Electric's current capital plan includes an estimated $81 million of compliance-related expenditures, including $54 million for 2024 through 2028. Projected capital expenditures are expected to decrease as a result of the planned conversion of the Belle River power plant to natural gas and the retirement of Monroe power plant generating units. However, discussions with the state are ongoing and a revised cost estimate has not yet been determined.

As part of the Monroe power plant NPDES permit, EGLE has added requirements to evaluate the thermal discharge of the facility as it relates to Clean Water Act section 316(a) regulations. DTE Electric has submitted to EGLE a biological demonstration study plan to evaluate the thermal discharge impacts to an aquatic community. After approval of the plan by EGLE and completion of field sampling, data will be processed and compiled into a comprehensive report. At the present time, DTE Electric cannot predict the outcome of this evaluation or financial impact.

Contaminated and Other Sites — Prior to the construction of major interstate natural gas pipelines, gas for heating and other uses was manufactured locally from processes involving coal, coke, or oil. The facilities, which produced gas, have been designated as MGP sites. DTE Electric conducted remedial investigations at contaminated sites, including three former MGP sites. Cleanup of one of the MGP sites is complete, and that site is closed. The investigations have revealed contamination related to the by-products of gas manufacturing at each MGP site. In addition to the MGP sites, DTE Electric is also in the process of cleaning up other contaminated sites, including the area surrounding an ash landfill, electrical distribution substations, electric generating power plants, and underground and above ground storage tank locations. The findings of these investigations indicated that the estimated cost to remediate these sites is expected to be incurred over the next several years. At March 31, 2024 and December 31, 2023, DTE Electric had $9 million accrued for remediation. These costs are not discounted to their present value. Any change in assumptions, such as remediation techniques, nature and extent of contamination, and regulatory requirements, could impact the estimate of remedial action costs for the sites and affect DTE Electric’s financial position and cash flows. DTE Electric believes the likelihood of a material change to the accrued amount is remote based on current knowledge of the conditions at each site.

Coal Combustion Residuals and Effluent Limitations Guidelines — A final EPA rule for the disposal of coal combustion residuals, commonly known as coal ash, became effective in October 2015 and has continued to be updated in subsequent years. The rule is based on the continued listing of coal ash as a non-hazardous waste and relies on various self-implementation design and performance standards. DTE Electric owns and operates three permitted engineered coal ash storage facilities to dispose of coal ash from coal-fired power plants and operates a number of smaller impoundments at its power plants subject to certain provisions in the CCR rule. At certain facilities, the rule required ongoing sampling and testing of monitoring wells, compliance with groundwater standards, and the closure of basins at the end of the useful life of the associated power plant.

On August 28, 2020, Part A of the CCR rule was published in the Federal Register and required all unlined impoundments to initiate closure as soon as technically feasible, but no later than April 11, 2021. Additionally, the rule amends certain reporting requirements and CCR website requirements. On November 12, 2020, Part B of the CCR Rule was published in the Federal Register and provides a process to determine if certain unlined impoundments with an alternative liner system may be sufficiently protective and therefore may continue to operate.

DTE Electric submitted applications to the EPA that support continued use of all impoundments through their active lives. DTE Electric subsequently ceased receipt of waste at the St. Clair power plant bottom ash basins and initiated closure, resulting in withdrawal of the Part A demonstration for the plant. Additionally, DTE Electric implemented projects at the Belle River and Monroe power plants to cease receipt of waste within any unlined CCR impoundments, resulting in withdrawals of the Part B applications for those plants.

On May 18, 2023, the EPA posted in the Federal Register a proposed rule to regulate legacy CCR surface impoundments and CCR management units. The rule proposes to expand the reach of the CCR rule to inactive electric generation sites and previously unregulated locations of CCR at a regulated facility. DTE Electric is currently evaluating the proposed rule. The financial impact of the proposed rule cannot be estimated until a final rule is issued, which is currently expected in mid-2024.

At the state level, legislation was signed in December 2018 and provides for further regulation of the CCR program in Michigan. Additionally, the statutory revision provides the basis of a CCR program that EGLE has submitted to the EPA for approval to fully regulate the CCR program in Michigan in lieu of a federal permit program. The EPA is currently working with EGLE in reviewing the submitted state program, and DTE Electric will work with EGLE to implement the state program that may be approved in the future.

On October 13, 2020, the EPA finalized the ELG Reconsideration Rule which revised the regulations from the 2015 ELG rule for FGD wastewater and bottom ash transport water only. The Reconsideration Rule re-established the technology-based effluent limitations guidelines and standards applicable to FGD wastewater and bottom ash transport water. The EPA set the applicability dates for bottom ash transport water "as soon as possible" beginning October 13, 2021 and no later than December 31, 2025. FGD wastewater retrofits must be completed "as soon as possible" beginning October 13, 2021 and no later than December 31, 2025 or December 31, 2028 if a permittee decides to pursue the Voluntary Incentives Program (VIP) subcategory for FGD wastewater. If a facility applies for the VIP, they must meet more stringent standards, but are allowed an extended time period to meet the compliance requirements.

The Reconsideration Rule also provides additional compliance opportunities by finalizing low utilization and cessation of coal burning subcategories. The Reconsideration Rule provides new opportunities for DTE Electric to evaluate existing ELG compliance strategies and make any necessary adjustments to ensure full compliance with the ELGs in a cost-effective manner.

Compliance schedules for individual facilities and individual waste streams are determined through issuance of new NPDES permits by the state of Michigan. The state of Michigan has issued an NPDES permit for the Belle River power plant establishing compliance deadlines based on the 2020 Reconsideration Rule. On October 11, 2021, in consideration of the deadlines above, DTE Electric submitted a Notice of Planned Participation ("NOPP") to the state of Michigan that formally announced the intent to pursue compliance subcategories as ELG compliance options: the cessation of coal at the Belle River power plant no later than December 31, 2028 and the VIP for FGD wastewater at Monroe power plant by December 31, 2028.

On March 29, 2023, the EPA published two draft proposals to revise existing ELG rules. The first draft proposal reopened the cessation of coal compliance subcategory from the 2020 ELG rule and allows for compliance by committing to such cessation no later than December 31, 2028. This proposal was finalized by the EPA on May 30, 2023. The second draft proposal is a broader update to the ELG rules that includes revised compliance standards for FGD wastewater, bottom ash transport water, and other wastewater streams with a compliance date no later than December 31, 2029. DTE Electric's compliance strategy includes the conversion of the two generating units at the Belle River power plant to a natural gas peaking resource in 2025-2026, which was included in the NOPP filed in 2021. DTE Electric also submitted a new NOPP to apply for the cessation of coal compliance subcategory for generating units 3 and 4 at the Monroe power plant. DTE Electric plans to retire Monroe's generating units 1 and 2 in 2032.

DTE Electric currently estimates the impact of the CCR and ELG rules to be $412 million of capital expenditures, including $403 million for 2024 through 2028. This estimate may change in future periods as DTE Electric evaluates the CCR and ELG rules discussed above that are expected to be finalized in mid-2024.

Contaminated and Other Sites — DTE Gas owns or previously owned 14 former MGP sites. Investigations have revealed contamination related to the by-products of gas manufacturing at each site. Cleanup of eight MGP sites is complete and those sites are closed. DTE Gas has also completed partial closure of four additional sites. Cleanup activities associated with the remaining sites will continue over the next several years. The MPSC has established a cost deferral and rate recovery mechanism for investigation and remediation costs incurred at former MGP sites. In addition to the MGP sites, DTE Gas is also in the process of cleaning up other contaminated sites, including gate stations, gas pipeline releases, and underground storage tank locations. As of March 31, 2024 and December 31, 2023, DTE Gas had $26 million accrued for remediation. These costs are not discounted to their present value. Any change in assumptions, such as remediation techniques, nature and extent of contamination, and regulatory requirements, could impact the estimate of remedial action costs for the sites and affect DTE Gas' financial position and cash flows. DTE Gas anticipates the cost amortization methodology approved by the MPSC, which allows for amortization of the MGP costs over a ten-year period beginning with the year subsequent to the year the MGP costs were incurred, will prevent the associated investigation and remediation costs from having a material adverse impact on DTE Gas' results of operations.

As noted above for DTE Electric, the EPA finalized the NAAQS for fine particulate matter in March 2024. It is likely that areas of Michigan in which DTE Gas operates will be designated as non-attainment in the future and the state will be required to develop a SIP for such areas. No impact is expected in the near term, and any long-term financial impacts cannot be assessed at this time.

In March 2019, the EPA issued an FOV to EES Coke Battery, LLC ("EES Coke"), the Michigan coke battery facility that is a wholly-owned subsidiary of DTE Energy, alleging that the 2008 and 2014 permits issued by EGLE did not comply with the Clean Air Act. In September 2020, the EPA issued another FOV alleging EES Coke's 2018 and 2019 SO2 emissions exceeded projections and hence violated non-attainment new source review permitting requirements. EES Coke evaluated the EPA's alleged violations and believes that the permits approved by EGLE complied with the Clean Air Act. EES Coke responded to the EPA's September 2020 allegations demonstrating its actual emissions are compliant with non-attainment new source review requirements. On June 1, 2022, the U.S. Department of Justice, on behalf of the EPA, filed a complaint against EES Coke in the U.S. District Court for the Eastern District of Michigan alleging that EES Coke failed to comply with non-attainment new source review requirements under the Clean Air Act when it applied for the 2014 permit. In November 2022, the Sierra Club and City of River Rouge were granted intervention. The case is currently in the discovery phase and trial is scheduled for April 2025. At the present time, DTE Energy cannot predict the outcome or financial impact of this matter.

In 2010, the EPA finalized a new one-hour SO2 ambient air quality standard that requires states to submit plans and associated timelines for non-attainment areas that demonstrate attainment with the new SO2 standard in phases. Phase 1 addresses non-attainment areas designated based on ambient monitoring data. Phase 2 addresses non-attainment areas with large sources of SO2 and modeled concentrations exceeding the National Ambient Air Quality Standards for SO2. Phase 3 addresses smaller sources of SO2 with modeled or monitored exceedances of the new SO2 standard.

Michigan's Phase 2 non-attainment area includes DTE Electric facilities in St. Clair County. The EPA approved a clean data determination request submitted by EGLE. This determination suspends certain planning requirements and sanctions for the non-attainment area for as long as the area continues to attain the 2010 SO2 air quality standards, but this does not automatically redesignate the area to attainment. Until the area is officially redesignated as attainment, DTE Energy is unable to determine the impacts.

DTE Energy provided certain guarantees and indemnities in conjunction with the sales of interests in or lease of its previously operated REF facilities. The guarantees cover potential commercial, environmental, and tax-related obligations that will survive until 90 days after expiration of all applicable statutes of limitations. DTE Energy estimates that its maximum potential liability under these guarantees at March 31, 2024 was $392 million. Payments under these guarantees are considered remote.

In certain limited circumstances, the Registrants enter into contractual guarantees. The Registrants may guarantee another entity’s obligation in the event it fails to perform and may provide guarantees in certain indemnification agreements. The Registrants may also provide indirect guarantees for the indebtedness of others. DTE Energy’s guarantees are not individually material with maximum potential payments totaling $44 million at March 31, 2024. Payments under these guarantees are considered remote.

The Registrants are periodically required to obtain performance surety bonds in support of obligations to various governmental entities and other companies in connection with its operations. As of March 31, 2024, DTE Energy had $334 million of performance bonds outstanding, including $159 million for DTE Electric. Performance bonds are not individually material, except for $130 million of bonds supporting Energy Trading operations. These bonds are meant to provide counterparties with additional assurance that Energy Trading will meet its contractual obligations for various commercial transactions. The terms of the bonds align with those of the underlying Energy Trading contracts and are estimated to be outstanding approximately 1 to 3 years. In the event that any performance bonds are called for nonperformance, the Registrants would be obligated to reimburse the issuer of the performance bond. The Registrants are released from the performance bonds as the contractual performance is completed and does not believe that a material amount of any currently outstanding performance bonds will be called.

There are several bargaining units for DTE Energy subsidiaries' approximately 4,900 represented employees, including DTE Electric's approximately 2,550 represented employees. This represents 51% and 59% of DTE Energy's and DTE Electric's total employees, respectively. Of these represented employees, approximately 8% have contracts expiring within one year for DTE Energy. None of the represented employees have contracts expiring within one year for DTE Electric.

DTE Electric and Consumers Energy Company ("Consumers"), joint owners of the Ludington Hydroelectric Pumped Storage plant ("Ludington"), are parties to a 2010 engineering, procurement, and construction agreement with Toshiba America Energy Systems ("TAES"), under which TAES contracted to perform a major overhaul and upgrade of Ludington. The overhauled Ludington units are operational, but TAES' work has been defective and non-conforming. DTE Electric and Consumers have demanded that TAES provide a comprehensive plan to resolve those matters, including adherence to its warranty commitments and other contractual obligations. DTE Electric and Consumers have taken extensive efforts to resolve these issues with TAES, including a formal demand to TAES' parent, Toshiba Corporation, under a parent guaranty it provided. TAES has not provided a comprehensive plan or otherwise met its performance obligations. In order to enforce the contract, DTE Electric and Consumers filed a complaint against TAES and Toshiba Corporation in the U.S. District Court for the Eastern District of Michigan in April 2022.

In June 2022, TAES and Toshiba Corporation filed a motion to dismiss the complaint, along with counterclaims seeking approximately $15 million in damages related to payments allegedly owed under the parties' contract. During September 2022, the motion to dismiss the complaint was denied. DTE Electric believes the outstanding counterclaims are without merit, but would be liable for 49% of the damages if approved. In October 2022, the combined parties submitted a joint discovery plan to proceed with the litigation process and a potential trial during the second half of 2024. DTE Electric cannot predict the financial impact or outcome of this matter.

In May 2023, the MPSC approved a jointly-filed request by DTE Electric and Consumers for authority to defer as a regulatory asset the costs associated with repairing or replacing the defective work performed by TAES while the litigation with TAES and Toshiba Corporation moves forward. Such costs will be offset by any potential litigation proceeds received from TAES or Toshiba Corporation. DTE Electric and Consumers will have the opportunity to seek recovery and ratemaking treatment for amounts which are not recovered from TAES or Toshiba Corporation.

The Registrants are involved in certain other legal, regulatory, administrative, and environmental proceedings before various courts, arbitration panels, and governmental agencies concerning claims arising in the ordinary course of business. These proceedings include certain contract disputes, additional environmental reviews and investigations, audits, inquiries from various regulators, and pending judicial matters. The Registrants cannot predict the final disposition of such proceedings. The Registrants regularly review legal matters and record provisions for claims that they can estimate and are considered probable of loss. The resolution of these pending proceedings is not expected to have a material effect on the Registrants' Consolidated Financial Statements in the periods they are resolved.