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Pension and Other Postretirement Employee Benefits (OPEB) Plans
 12 Months Ended
Dec. 31, 2023
Compensation and Retirement Benefits Disclosures [Abstract]  
Pension and Other Postretirement Employee Benefits (OPEB) Plans PENSION AND OTHER POSTRETIREMENT EMPLOYEE BENEFITS (OPEB) PLANS
Vistra is the plan sponsor of the Vistra Retirement Plan (the Retirement Plan), which provides benefits to eligible employees of its subsidiaries. Oncor is a participant in the Retirement Plan. As Vistra accounts for its interests in the Retirement Plan as a multiple employer plan, only Vistra's share of the plan assets and obligations are reported in the pension benefit information presented below. After amendments in 2012, employees in the Retirement Plan now consist entirely of participants who were active and retired collective bargaining unit employees. The Retirement Plan is a qualified defined benefit pension plan under Section 401(a) of the Internal Revenue Code of 1986, as amended (Code), and is subject to the provisions of ERISA. The Retirement Plan provides benefits to participants under one of two formulas: (i) a Cash Balance Formula under which participants earn monthly contribution credits based on their compensation and a combination of their age and years of service, plus monthly interest credits or (ii) a Traditional Retirement Plan Formula based on years of service and the average earnings of the three years of highest earnings. Under the Cash Balance Formula, future increases in earnings will not apply to prior service costs. It is our policy to fund the Retirement Plan assets only to the extent required under existing federal regulations.
Vistra and our participating subsidiaries offer other postretirement employee benefits (OPEB) in the form of certain health care and life insurance benefits to eligible retirees and their eligible dependents. The retiree contributions required for such coverage vary based on a formula depending on the retiree's age and years of service.

Effective January 1, 2018, Vistra entered into a contractual arrangement with Oncor whereby the costs associated with providing OPEB coverage for certain retirees (Split Participants) whose employment included service with both the regulated businesses of Oncor (or its predecessors) and the non-regulated businesses of Vistra (or its predecessors) are split between Oncor and Vistra. As Vistra accounts for its interest in this OPEB plan as a multiple employer plan, only Vistra's share of the plan assets and obligations are reported in the OPEB information presented below. In addition, Vistra is the sponsor of OPEB plans that certain EFH Corp. and Dynegy retirees participate in.

Pension and OPEB Costs
Year Ended December 31,
202320222021
Pension costs$9 $2 $6 
OPEB costs5 4 8 
Total benefit costs recognized as expense$14 $6 $14 

Market-Related Value of Assets Held in Pension Benefit Trusts

We use the calculated value method to determine the market-related value of the assets held in the trust for purposes of calculating pension costs. We include all gains or losses in the market-related value of assets over a rolling four-year period. Each year, 25% of such gains and losses for the current year and for each of the preceding three years is included in the market-related value. Each year, the market-related value of assets is increased for contributions to the plan and investment income and is decreased for benefit payments and expenses for that year.
Detailed Information Regarding Pension Plans and OPEB Benefits

The following information is based on a December 31, 2023, 2022 and 2021 measurement dates:
Retirement PlanOPEB Plans
Year Ended December 31,Year Ended December 31,
202320222021202320222021
Assumptions Used to Determine Net Periodic Pension and Benefit Cost:
Discount rate5.16 %2.84 %2.50 %5.18 %2.87 %2.51 %
Expected rate of compensation increase3.79 %3.49 %3.41 %
Interest crediting rate for cash balance3.00 %3.00 %3.00 %
Expected return on plan assets (Vistra Plan)5.85 %4.24 %3.77 %
Expected return on plan assets (Dynegy Plan)5.85 %4.77 %4.42 %
Expected return on plan assets (EEI Plan)— %4.92 %4.72 %
Expected return on plan assets (EEI Union)3.89 %3.92 %6.79 %
Expected return on plan assets (EEI Salaried)4.85 %3.41 %2.95 %
Components of Net Pension and Benefit Cost:
Service cost$3 $4 $5 $1 $1 $1 
Interest cost21 17 16 5 4 4 
Expected return on assets(18)(19)(18)(1)(1)(2)
Amortization of unrecognized amounts, net3 — 3 — — 5 
Net periodic pension and OPEB cost$9 $2 $6 $5 $4 $8 
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net (gain) loss$7 $(16)$(27)$— $(22)$(10)
Prior service (credit) cost(6)9 — — — (2)
Curtailment and settlements— — (2)— — — 
Total recognized in net periodic benefit cost and other comprehensive income$10 $(5)$(23)$5 $(18)$(4)
Assumptions Used to Determine Benefit Obligations at Period End:
Discount rate4.97 %5.16 %2.84 %4.98 %5.18 %2.87 %
Expected rate of compensation increase3.64 %3.79 %3.49 %
Interest crediting rate for cash balance plans3.50 %3.00 %3.00 %

Net Actuarial Gains (Losses)

Retirement Plan

For the year ended December 31, 2023, the net actuarial loss of $5 million that occurred for the pension plans during 2023 was a result of losses attributable to decreasing discount rates due to changes in the corporate bond markets and losses attributable to actuarial assumption updates to reflect current market conditions, plan experience different than expected, and settlements, partially offset by a gain attributable to actual asset performance exceeding expectations. The Dynegy Pension Plan was amended during 2023 to extend the lump sum interest rates from calendar year 2022 through 2024 and provide in-service distributions for certain eligible employees as of December 31, 2022. As a result, the pension obligation increased by $1 million and a prior service cost was created to be amortized over 2 years.

For the year ended December 31, 2022, the net actuarial gain of $16 million was driven by gains attributable to increasing discount rates due to changes in the corporate bond markets, gains attributable to actuarial assumption updates to reflect current market conditions and plan experience different than expected, partially offset by losses attributable to actual asset performance falling short of expectations and settlements.
For the year ended December 31, 2021, the net actuarial gain of $24 million was driven by gains attributable to increasing discount rates due to changes in the corporate bond markets and gains attributable to actual asset performance exceeding expectations, partially offset by losses attributable to demographic assumption updates to reflect recent plan experience, actuarial assumption updates to reflect current market conditions, plan amendments, settlements and plan experience different than expected.

OPEB Plans

For the year ended December 31, 2023, the immaterial net actuarial loss that occurred for the OPEB plans during 2023 was a result of losses attributable to decreasing discount rates due to changes in the corporate bond markets, partially offset by gains attributable to plan experience different than expected, updates to health care assumptions, and actual asset performance exceeding expectations.

For the year ended December 31, 2022, the net actuarial gain of $22 million was driven by gains attributable to increasing discount rates due to changes in the corporate bond markets, plan experience different than expected and updates to health care assumptions, partially offset by losses attributable to actual asset performance falling short of expectations.

For the period ended December 31, 2021, the net actuarial gain of $7 million was driven by gains attributable to increasing discount rates due to changes in the corporate bond markets, plan experience different than expected, updates to health care claims and trend assumptions and actual asset performance exceeding expectations, partially offset by losses attributable to demographic assumption updates and life expectancy updates.
Retirement PlanOPEB Plans
Year Ended December 31,Year Ended December 31,
2023202220232022
Change in Pension and Postretirement Benefit Obligations:
Projected benefit obligation at beginning of period$449 $605 $110 $146 
Service cost3 4 1 1 
Interest cost21 17 5 4 
Participant contributions— — 3 2 
Plan amendments1 9 — — 
Actuarial (gain) loss10 (113)1 (30)
Benefits paid(59)(73)(12)(13)
Projected benefit obligation at end of year$425 $449 $108 $110 
Accumulated benefit obligation at end of year$422 $447 $— $— 
Change in Plan Assets:
Fair value of assets at beginning of period$320 $470 $29 $39 
Employer contributions— — 9 9 
Participant contributions— — 3 2 
Actual gain (loss) on assets24 (77)2 (6)
Transfers— — (19)(2)
Benefits paid(59)(73)(12)(13)
Fair value of assets at end of year$285 $320 $12 $29 
Funded Status:
Projected benefit obligation$(425)$(449)$(108)$(110)
Fair value of assets285 320 12 29 
Funded status at end of year$(140)$(129)$(96)$(81)
Amounts Recognized in the Balance Sheet Consist of:
Investments$— $— $3 $20 
Other current liabilities— — (9)(8)
Other noncurrent liabilities(140)(129)(90)(93)
Net liability recognized$(140)$(129)$(96)$(81)
Amounts Recognized in Accumulated Other Comprehensive Income Consist of:
Net actuarial (gain) loss$4 $(4)$(15)$(15)
Prior services cost3 9 1 1 
Net (income) loss and prior service cost$7 $5 $(14)$(14)
Fair Value Measurement of Pension and OPEB Plan Assets

Retirement Plan

As of December 31, 2023 and 2022, all of the Retirement Plan assets were measured at fair value using the net asset value per share (or its equivalent) except as noted and consisted of the following:
December 31,
20232022
Asset Category:
Interest-bearing cash (a)$— $2 
Cash commingled trusts4 4 
Equity securities:
Global equities82 80 
Fixed income securities:
Corporate bonds (b)82 107 
Government bonds54 44 
Other (c)18 24 
Real estate28 43 
Hedge funds17 16 
Total assets measured at net asset value$285 $320 
___________
(a)Interest -bearing cash is classified as Level 2.
(b)Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody's.
(c)Consists primarily of high-yield bonds, emerging market debt, bank loans, securitized bonds and private investment grade fixed income.

OPEB Plans

As of December 31, 2023 and 2022, the Vistra OPEB plan assets measured at fair value totaled $12 million and $29 million, respectively. At December 31, 2023 and 2022, assets consisted of $9 million and $28 million, respectively, of comingled funds valued at net asset value and $3 million and $1 million, respectively, of municipal bond and cash equivalent mutual funds classified as Level 1.

Pension Plans with Projected Benefit Obligations (PBO) and Accumulated Benefit Obligations (ABO) in Excess of Plan Assets

The following table provides information regarding pension plans with PBO and ABO in excess of the fair value of plan assets.
December 31,
20232022
Pension Plans with PBO and ABO in Excess of Plan Assets:
Projected benefit obligations$425 $449 
Accumulated benefit obligation$422 $447 
Plan assets$285 $320 

Retirement Plan Investment Strategy and Asset Allocations

Our investment objective for the Retirement Plan is to invest in a suitable mix of assets to meet the future benefit obligations at an acceptable level of risk, while minimizing the volatility of contributions. Fixed income securities held primarily consist of corporate bonds from a diversified range of companies, U.S. Treasuries and agency securities and money market instruments. Equity securities are held to enhance returns by participating in a wide range of investment opportunities. International equity securities are used to further diversify the equity portfolio and may include investments in both developed and emerging markets. Real estate, hedge funds and credit strategies (primarily high yield bonds and emerging market debt) provide additional portfolio diversification and return potential.
The target asset allocation ranges of pension plan investments by asset category are as follows:
Target Allocation Ranges
Asset Category:Vistra PlanDynegy Plan
Fixed income securities50 %-70%40 %-50%
Global equity securities20 %-28%28 %-38%
Real estate6 %-10%7 %-15%
Credit strategies2 %-6%4 %-8%
Hedge funds2 %-6%4 %-8%

Retirement Plan Expected Long-Term Rate of Return on Assets Assumption

The Retirement Plan strategic asset allocation is determined in conjunction with the plan's advisors and utilizes a comprehensive Asset-Liability modeling approach to evaluate potential long-term outcomes of various investment strategies. The study incorporates long-term rate of return assumptions for each asset class based on historical and future expected asset class returns, current market conditions, rate of inflation, current prospects for economic growth, and taking into account the diversification benefits of investing in multiple asset classes and potential benefits of employing active investment management.
Retirement Plan
Expected Long-Term Rate of Return
Asset Class:Vistra PlanDynegy Plan
Fixed income securities5.3 %5.1 %
Global equity securities7.4 %7.4 %
Real estate5.5 %5.5 %
Credit strategies6.5 %6.5 %
Hedge funds7.3 %7.3 %
Weighted average5.9 %6.1 %

Benefit Plan Assumed Health Care Cost Trend Rates

The following tables provide information regarding the assumed health care cost trend rates.
December 31,
20232022
Assumed Health Care Cost Trend Rates-Not Medicare Eligible:
Health care cost trend rate assumed for next year7.00 %6.80 %
Rate to which the cost trend is expected to decline (the ultimate trend rate)4.50 %4.50 %
Year that the rate reaches the ultimate trend rate20332032
Assumed Health Care Cost Trend Rates-Medicare Eligible:
Health care cost trend rate assumed for next year (Vistra Plan)12.90 %10.30 %
Health care cost trend rate assumed for next year (Split-Participant Plan)12.30 %10.00 %
Rate to which the cost trend is expected to decline (the ultimate trend rate)4.50 %4.50 %
Year that the rate reaches the ultimate trend rate20332032

Significant Concentrations of Risk

The plans' investments are exposed to risks such as interest rate, capital market and credit risks. We seek to optimize return on investment consistent with levels of liquidity and investment risk which are prudent and reasonable, given prevailing capital market conditions and other factors specific to us. While we recognize the importance of return, investments will be diversified in order to minimize the risk of large losses unless, under the circumstances, it is clearly prudent not to do so. There are also various restrictions and guidelines in place including limitations on types of investments allowed and portfolio weightings for certain investment securities to assist in the mitigation of the risk of large losses.
Assumed Discount Rate

We selected the assumed discount rates using the Aon AA Above Median yield curve, which is based on corporate bond yields and at December 31, 2023 consisted of 509 corporate bonds with an average rating of AA using Moody's, S&P and Fitch ratings.

Contributions

Contributions to the Retirement Plan for the years ended December 31, 2023, 2022 and 2021 totaled zero, zero and $1 million, respectively, and contributions in 2024 are expected to total $14 million. OPEB plan funding for each of the years ended December 31, 2023, 2022 and 2021 totaled $9 million, and funding in 2024 is expected to total $9 million.

Future Benefit Payments

Estimated future benefit payments to beneficiaries are as follows:
202420252026202720282029-2033
Pension benefits$52 $30 $36 $37 $29 $142 
OPEB$10 $9 $9 $9 $8 $37 

Qualified Savings Plans

Our employees may participate in a qualified savings plan (the Thrift Plan). This plan is a participant-directed defined contribution plan intended to qualify under Section 401(a) of the Code and is subject to the provisions of ERISA. Under the terms of the Thrift Plan, employees who do not earn more than the IRS threshold compensation limit used to determine highly compensated employees may contribute, through pre-tax salary deferrals and/or after-tax payroll deductions, the lesser of 75% of their regular salary or wages or the maximum amount permitted under applicable law. Employees who earn more than such threshold may contribute from 1% to 20% of their regular salary or wages. Employer matching contributions are also made in an amount equal to 100% (75% for employees covered under the traditional formula in the Retirement Plan) of the first 6% of employee contributions. Employer matching contributions are made in cash and may be allocated by participants to any of the plan's investment options.

Aggregate employer contributions to the qualified savings plans totaled $33 million, $33 million and $34 million for the years ended December 31, 2023, 2022 and 2021, respectively.