Reliant Energy, Incorporated and American Electric Power Company v. Public Utility Commission of Texas ( 2003 )


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  •          TEXAS COURT OF APPEALS, THIRD DISTRICT, AT AUSTIN
    NO. 03-02-00001-CV
    Reliant Energy, Incorporated and American Electric Power Company, Appellants
    v.
    Public Utility Commission of Texas, Appellee
    DIRECT APPEAL FROM THE PUBLIC UTILITY COMMISSION OF TEXAS
    OPINION
    In this direct appeal, we must determine whether the Public Utility Commission
    erred in promulgating a rule governing stranded-cost recovery for formerly regulated electric
    utilities. See Tex. Util. Code Ann. ' 39.001(e), (f) (West Supp. 2003). Stranded costs represent
    prudently incurred expenditures made by the utilities during regulationCpreviously recoverable
    over time through regulated ratesCthat have become unrecoverable in a deregulated market.
    Utilities are permitted to recover their stranded costs as part of the transition to competition in
    Texas. Reliant Energy, Incorporated and American Electric Power Company (AAEP@) argue that
    the Public Utility Commission1 exceeded its authority by promulgating portions of substantive rule
    25.263, which governs the proceeding where the Commission is to determine whether a utility
    actually has stranded costs and to reconcile a utility=s actual stranded costs with amounts already
    recovered based on previous estimates. We hold that the Commission exceeded its authority in
    promulgating some of the challenged portions of its rule and reverse and remand those portions to
    the Commission for further proceedings in accordance with this opinion. See Tex. Util. Code Ann.
    ' 39.001(f). We affirm the remaining portions of the rule as enacted. See 
    id. BACKGROUND 1
              In addition to the Commission, several intervenors argue in support of the rule. They include the
    Office of Public Utility Counsel (OPUC), the Steering Committee for Cities Served by TXU Electric and
    Central Power and Light Company (SCC), Texas Industrial Energy Consumers (TIEC), the State of Texas,
    and the Alliance for Retail Markets (ARM). TXU Electric Company was also a party to this appeal but it
    has since settled with the Commission and filed a motion to dismiss. We have granted TXU=s motion and
    dismissed its claims.
    2
    In 1975, the legislature enacted the Public Utility Regulatory Act (PURA) creating
    the Public Utility Commission and establishing a comprehensive regulatory regime for electric
    utilities. At that time, it was thought that electric utilities were natural monopolies, immune from
    the normal forces of competition. Under the regulatory regime created by PURA, each utility was
    allowed to operate as a monopoly in the area it served but was prohibited from charging monopoly
    prices. The Commission was authorized to set rates for each utility at a level that would allow it
    to recoup its prudently incurred costs and to earn a reasonable return on its investments.2 See 16
    Tex. Admin. Code '' 25.231, .235(a) (2002); see also Central Power & Light Co. v. Public Util.
    Comm=n, 36 S.W.3d. 547, 553 (Tex. App.CAustin 2000, pet. denied) (describing utility ratemaking
    procedure under regulation).
    When the legislature enacted PURA most electric utilities were large vertically
    integrated companies that produced, transported, and retailed electricity. In truth, only one
    2
    The utilities could recoup, among other things, the following expenses if reasonably incurred:
    $ operation and maintenance costs incurred in furnishing normal service and in
    maintaining plants
    $ assessed taxes
    $ fuel and purchased power costs
    $ ordinary advertising costs
    $ post-retirement benefit-plan costs
    $ costs of certain assets through depreciation
    See 16 Tex. Admin. Code '' 25.231, .235(a) (2002).
    3
    component of a vertically integrated electric utility immunizes it from the normal forces of
    competitionCits transmission and distribution infrastructure. Recognizing this, the legislature amended
    PURA in 1999 and partially deregulated the industry. Among its Apolicies and purposes,@ the legislature
    found that:
    [T]he production and sale of electricity is not a monopoly warranting regulation of rates,
    operations, and services and that the public interest in competitive electric markets requires
    that, except for transmission and distribution services and for the recovery of stranded
    costs, electric services and their prices should be determined by customer choices and the
    normal forces of competition.
    Tex. Util. Code Ann. ' 39.001(a) (West Supp. 2003).
    Chapter thirty-nine of PURA governs the restructuring of the electric-utility industry. As of
    January 1, 2000, each privately owned electric utility was required to Aunbundle@ or separate into the
    following entities: a power generation company, a retail electric provider, and a transmission and distribution
    utility. See 
    id. ' 39.051(b)
    (West Supp. 2003). The former vertically integrated utilities can now operate
    as holding companies that own affiliated unbundled entities. See 
    id. ' 39.051(c)
    (West Supp. 2003).
    Under deregulation, the power generation and retail markets are to be governed by Acustomer choices and
    the normal forces of competition,@ while the Commission is to continue to regulate transmission and
    distribution utilities. See 
    id. ' 39.001(a).
    The Commission is also charged with facilitating stranded-cost
    recovery for the formerly regulated utilities. See 
    id. Chapter thirty-nine
    defines stranded costs as Athe positive excess of the net book value of
    generation assets over the market value of those assets. . . .@ See 
    id. ' 39.251(7)
    (West Supp. 2003). The
    4
    basic concept of stranded costs is straightforward. Under regulation, a utility could recover over time its
    prudently incurred costs of acquiring power-generation assets through rates approved by the
    Commission and paid by captive customers. See Central Power & Light 
    Co., 36 S.W.3d at 552
    -
    53. The Commission facilitated this cost recovery by incorporating depreciation expenses into
    approved rates. See 
    id. at 53.
    But in a deregulated environment, it was thought that competition
    might drive rates to levels so low that a formerly regulated utility would be unable to recoup its
    investments. Stranded costs represent that portion of the net book value of a utility=s generation
    assets not yet recovered through depreciation that has become unrecoverable in a deregulated
    environment. See City of Corpus Christi v. Public Util. Comm=n, 
    51 S.W.3d 231
    , 237-38 (Tex.
    2001); Tex. Util. Code Ann. ' 39.251(7).
    Chapter thirty-nine sets out a three-stage program for the recovery of stranded
    costs. In the first stage, from September 1999 to December 2001, the Commission froze retail
    electric rates. See Tex. Util. Code Ann. '' 39.052(a), .254-.256 (West Supp. 2003). During this
    stage, utilities identified as having probable stranded costs 3 were required to Amitigate@ them
    through various measures intended to reduce the book value of their generation assets. See 
    id. They could
    shift depreciation from transmission and distribution assets to generation assets, 
    id. ' 39.256;
    they could keep earnings in excess of the allowed rate of return, 
    id. ' 39.254.
    These
    utilities were also allowed to Asecuritize @ a portion of their estimated stranded costs by selling
    3
    These utilities were identified in an April 1998 Commission Report to the Texas Senate
    Interim Committee on Electric Utility Restructuring. In making these estimates, the Commission
    utilized an AExcess Cost Over Market@ computer model (ECOM model).
    5
    transition bonds and using the proceeds to reduce the book value of their generation assets. See
    
    id. '' 39.301-.313
    (West Supp. 2003). The costs of issuing and servicing transition bonds are
    borne by all retail customers in a utility=s service area through a nonbypassable Atransition
    charge.@ See 
    id. '' 39.302(7),
    .303(b), (c); City of Corpus 
    Christi, 51 S.W.3d at 239
    . Because the
    Commission estimated in 1998 that the appellant utilities would have significant stranded costs in
    a deregulated environment, each utility        used the available mitigation procedures and
    securitization to reduce the book value of their generation assets during this stage of PURA=s
    stranded-cost recovery program. 4
    The second stage began on January 1, 2002, the first day of competition. See Tex.
    Util. Code Ann. '' 39.001(b)(1), .201 (West Supp. 2003). During this stage, the Commission was
    4
    See generally Tex. Pub. Util. Comm=n, Application of Reliant Energy, Incorporated for
    Financing Order to Securitize Regulatory Assets and Other Qualified Costs, Docket No. 21655
    (2000); Tex. Pub Util. Comm=n, Application of Central Power and Light Company for Financing
    Order to Securitize Regulatory Assets and Other Qualified Costs, Docket No. 21528 (2000); Tex.
    Pub. Util. Comm=n, Application of Reliant Energy for Approval of Unbundled Cost of Service Rate
    Pursuant to PURA ' 39.201 and Public Utility Commission Substantive Rule ' 25.344, Docket No.
    22355 (2001); Tex. Pub. Util. Comm=n, Application of Central Power and Light Company for
    Approval of Unbundled Cost of Service Rate Pursuant to PURA ' 39.201 and Public Utility
    Commission Substantive Rule ' 25.344, Docket No. 22352 (2001).
    6
    authorized to set a nonbypassable Acompetition transition charge@ to allow utilities to recover any
    stranded costs remaining after the mitigation procedures and securitization utilized in stage one.
    See generally 
    id. ' 39.201.
    Any competition transition charge was to be included in the tariffs of a
    utility=s affiliated unbundled transmission and distribution utility. See 
    id. ' 39.201(b)(3).
    In
    determining whether to set such a charge, the Commission was required to revise its previous
    stranded-cost estimates using Aupdated company-specific inputs.@ See 
    id. ' 39.201(h).
    In preparation for the rate hearings for the transmission and distribution utilities to
    be held in 2001, the stranded cost estimates were updated. The Commission=s updated estimates
    unexpectedly reflected that the utilities would have no stranded costs.5 A substantial increase in
    natural gas prices in 2000 had driven the market value of the utilities= generation assets well
    above their book value. These new estimates therefore indicated that some utilities had been
    overcompensated by their earlier mitigation procedures and securitization.
    In light of these revised estimates, the Commission issued orders requiring the
    utilities to discontinue all mitigation efforts, to reassign the depreciation transferred from
    5
    See generally Tex. Pub. Util. Comm=n, Application of Reliant Energy for Approval of
    Unbundled Cost of Service Rate Pursuant to PURA ' 39.201 and Public Utility Commission
    Substantive Rule ' 25.344, Docket No. 22355, p. 139; Tex. Pub. Util. Comm=n, Application of Central
    Power and Light Company for Approval of Unbundled Cost of Service Rate Pursuant to PURA '
    39.201 and Public Utility Commission Substantive Rule ' 25.344, Docket No. 22352, p. 120.
    7
    transmission and distribution assets back to those assets, and to return monthly Aexcess
    mitigation credits@ to retail providers and their ratepayers. The Commission did not, however,
    require the utilities to refund the amounts they had received from selling transition bonds, and by
    statute it could not alter the transition charge that had been imposed on ratepayers to service the
    bonds. See 
    id. ' 39.303(d)
    (Transition charge authorized in financing order is Airrevocable and not
    subject to reduction, impairment, or adjustment by further action of the commission . . . .@).
    Utilities that had sold transition bonds to recover stranded costs no longer anticipated would seem
    to have received a windfall at the ratepayers = expense.
    The third and final stage of stranded-cost recovery is yet to occur. This stage
    requires the Commission to conduct a Atrue-up proceeding@ sometime after January 10, 2004, to
    determine whether a utility actually has remaining stranded costs. See 
    id. '' 39.201(l),
    .262(c)
    (West Supp. 2003). The challenged rule governs the conduct of this true -up proceeding. See 16
    Tex. Admin. Code ' 25.263 (2002). The goal of the true -up proceeding in this third stage is to
    determine the utility=s actual stranded costs and to reconcile or true up this determination with its
    previous estimates. See Tex. Util. Code Ann. '' 39.201(l), .262(c). This final determination is to
    be based on a new calculation of the value of a utility=s generation assets made under actual
    competitive conditions. See 
    id. The Commission
    is required to subtract the market value of a utility=s
    generation assets from the book value of those assets.6 See 
    id. '' 39.251(7),
    .252(a), .262(c), (h), (i)
    6
    The ECOM model remains applicable in 2004 only to the extent that a utility has nuclear assets
    that are not susceptible to market valuation under the methods described in PURA section 39.263(h). See
    Tex. Util. Code Ann. ' 39.262(i) (West Supp. 2003).
    8
    (West Supp. 2003). If the calculation yields a positive number, i.e., if the book value of the assets exceeds
    their market value, then the utility has stranded costs it is entitled to recover. If the calculation yields a
    negative number, i.e., if the market value of the assets exceeds their book value, the utility has no stranded
    costsCand chapter thirty-nine does not provide for any return to ratepayers of so called Anegative stranded
    costs.@ If this true-up proceeding reveals that the utilities over-recovered estimated stranded costs through
    their earlier mitigation efforts, the Commission can make appropriate adjustments by, among other things,
    reducing the unbundled transmission and distribution utility=s rates. See 
    id. ' 39.201(l).
    The Commission
    cannot, however, reduce the transition charge imposed on ratepayers to service transition bonds. See 
    id. ' 39.303(d)
    .
    In addition to finalizing stranded costs, chapter thirty-nine also requires that the
    Commission make several other Atrue-up@ calculations in the 2004 proceeding that could affect
    customer rates. See 
    id. ' 39.262(d)-(g)
    (West Supp. 2003). These calculations reconcile previous
    estimates with known values in various areas and result in either credits or bills to the
    transmission and distribution utility from its affiliated power generation company or retail electric
    provider. See generally 
    id. Based on
    these credits or bills, the transmission and distribution
    utility is to make adjustments to its nonbypassable delivery rates. See 
    id. ' 39.262(g).
    One of these several other true -up calculations involves the determination of a
    utility=s final fuel balance. See 
    id. '' 39.202(c),
    .262(d)(1) (West Supp. 2003). In the 2004
    proceeding, the Commission must true up the actual cost of fuel incurred by the utility against the prior
    estimate used to set the Afuel factor@ component of regulated rates during the final period of traditional
    9
    regulation. See 
    id. A positive
    fuel balance represents money owed to the utility for under-recovered fuel
    costs.7 See 
    id. The challenged
    portion of rule 25.263 would reduce this positive fuel balance owed to the
    utility by any negative stranded-cost calculationCregardless of whether the negative calculation was caused
    by market forces or by previous over-recovery through securitization. See 16 Tex. Admin. Code '
    25.263(l).
    The utilities argue that there is no such thing as negative stranded costs. They also complain
    that the fuel balance is not a stranded cost and therefore cannot be Anetted@ against a negative stranded-cost
    calculation. In other words, according to the utilities, the true-up proceeding was never intended to
    reconcile a negative stranded-cost calculation against a positive fuel-balance calculation to reduce the
    amount due to the utility for under-recovered fuel costs. The Commission insists that it has a mandate to
    prevent a utility from receiving an over-recovery of stranded costs and that offsetting sums due for a positive
    fuel balance is a permissible means of reversing an over-recovery of stranded costs achieved through
    securitization. We begin our analysis by examining how the rule works.
    THE RULE
    7
    A positive final fuel balance is to be recovered through the mechanism described above: each
    affiliated power generation company will bill the regulated transmission and distribution utility, which will, in
    turn, increase its nonbypassable delivery rates. See 
    id. '' 39.202(c),
    .262(d)(1), (g).
    10
    Rule 25.263 requires the relevant portion of the true -up proceeding to be
    conducted in four steps. First, the Commission subtracts the newly calculated market value 8 of
    the utility=s generation assets from the net book value of those assets. According to the statute,
    if this number is positive, the utility has recoverable stranded costs; if it is negative, the utility has
    no stranded costs.9 See Tex. Util. Code. Ann. '' 39.251(3), (7), .252(a) (West Supp. 2003). A
    negative number may be due to over-recovery of stranded costs that reduced the book value of
    assets during the first stage, but it may also result from unrelated market conditions that
    increased the market value of the assets.
    Second, the Commission calculates the utility=s final fuel balance, which is the
    differenceCpositive or negativeCbetween the estimated cost of fuel that was used to set the
    utility=s rates for the final period of regulation and the actual cost of fuel for that period. Under
    the prior regulatory regime, this amount would have been includedCas a credit or chargeCin the
    rates set at the utility=s next ratemaking proceeding. Under the challenged section of rule 25.263,
    this final fuel balance is netted against the actual stranded costs determined in step one. Thus, a
    8
    Chapter thirty-nine sets out several methods for calculating the market value of a utility=s
    generation assets. One part of rule 25.263 that the utilities challenge is the section that implements the
    Apartial stock valuation@ method. Compare Tex. Util. Code Ann. ' 39.262(h)(3), with 16 Tex. Admin.
    Code ' 25.263 (f)(1)(c) (2002).
    9
    There will sometimes be a third step. If a utility has nuclear assets that are not susceptible to the
    normal market valuation methods, the Commission conducts an updated ECOM estimate to determine
    whether investments in these assets are stranded and nets this calculation with stranded-cost determination
    for the rest of the assets. See Tex. Util. Code Ann. ' 39.262(i) (West Supp. 2003); 16 Tex. Admin. Code
    ' 25.263(f)(2) (2002).
    11
    negative stranded cost calculation could reduce or eliminate a positive fuel balance owed to the
    utility.
    Third, the Commission calculates a Acapacity-auction true-up@ amount, which is the
    difference between the price the utility, or its unbundled power generation affiliate, was estimated
    to obtain for its power on the wholesale market in the second stage and the price the utility
    actually received during the first two years of competition. See 16 Tex. Admin. Code '' 25.263(i),
    (l) (2002). The actual market price is reflected in Acapacity auctions @ in which the utility sold its
    entitlements to generation capacity to reduce its market share as a part of the transition to
    competition. See Tex. Util. Code Ann. '' 39.153, .156 (West Supp. 2003). The capacity-auction
    true-up amount must then be netted against the amount reached in step two by netting the
    stranded costs determined in step one with the fuel balance.
    Fourth, and finally, the Commission will conduct a prudence review of regulatory
    assets 10 not previously approved in a prior Commission rate order but being recovered through
    securitization in the form of a transition charge or through a competition transition charge
    imposed during the second stage of stranded-cost recovery. See 16 Tex. Admin. Code ' 25.263(l)
    (2002). If the Commission determines that these assets were not prudently incurred, it will
    10
    Regulatory assets are a subset of generation-related costs incurred by a utility. See City of
    Corpus Christi v. Public Util. Comm=n, 
    51 S.W.3d 231
    , 238 (Tex. 2001). They arise when the
    regulatory regime requires that a utility=s right to recover an expenditure be deferred over several years. See
    
    id. The right
    to recover this income stream in future years is carried on the utility=s books as a regulatory
    asset. See 
    id. Regulatory assets
    therefore have no market value absent a regulatory regime that assures
    their recovery. See 
    id. 12 subtract
    them from the true-up balance as determined in steps one through three. If the resulting
    final true-up balance is positive, the utility will be entitled to recover that amount through a
    competition transition charge assessed to its transmission and distribution customers. See 
    id. ' 25.263(l)(2)(A).
    If negative, the Commission will (1) reverse any existing competition transition
    charge, then (2) reverse any remaining mitigation proceeds, then (3) impose on utilities that have
    sold transition bonds a negative competition transition charge based on the lesser of the absolute
    value of the re maining negative true -up balance or the amount the utility has securitized. See 
    id. ' 25.263(l)(2)(C).
    13
    DISCUSSION
    This is a direct challenge to the validity of a chapter thirty-nine competition rule.
    See Tex. Util. Code Ann. ' 39.001(e). The utilities allege that certain portions of the rule exceed
    the Commission=s statutory authority.11 See id.; see generally City Pub. Serv. Bd. v. Public Util.
    Comm=n, No. 3-00-007-CV, slip op. at 8, 2002 Tex. App. LEXIS 2059, at *12 (Tex. App.
    AustinCMar. 21, 2002, no pet.). An administrative agency has only those powers conferred upon
    it by clear and unmistakable language. Public Util. Comm=n v. City Pub. Serv. Bd., 
    53 S.W.3d 310
    , 315-16 (Tex. 2001). When the legislature expressly confers a power on an agency, it also
    impliedly intends that the agency have whatever powers are reasonably necessary to fulfill its
    express functions or duties. Public Util. Comm=n v. GTE-Southwest, Inc., 
    901 S.W.2d 401
    , 407
    (Tex. 1995). An agency may not, however, exercise what is effectively a new power on the theory
    that such exercise is expedient for the agency=s purposes. 
    Id. at 407.
    We must therefore
    determine whether the Commission had either the express or implied authority to promulgate the
    challenged aspects of its rule that will govern the 2004 true -up proceedings.
    11
    We reject the Commission=s contention that the utilities= complaints are not properly
    brought as validity challenges because there may exist some hypothetical set of facts where the
    type of harm that the utilities predict might not actually occur. The utilities properly challenge the
    rule=s validity by arguing that several of its mandatory provisions were promulgated without
    14
    Netting
    PURA provides that A[a]n electric utility is allowed to recover all of its net,
    verifiable, nonmitigable stranded costs incurred in purchasing power and providing electric
    generation service.@ Tex. Util. Code Ann. ' 39.252(a). The utilities challenge the Commission=s
    authority to net a utility=s final stranded-cost calculation with other true-up items such as a
    utility=s final-fuel balance. The Commission defends its rule arguing that (1) these other true -up
    items are themselves potential stranded costs and, (2) even if they are not, netting is a
    permissible means of preventing over-recovery of stranded costs by those utilities that received a
    windfall through securitization.
    PURA defines stranded costs as follows:
    AStranded costs@ means the positive excess of the net book value of generation
    assets over the market value of those assets, taking into account all of the electric
    utility=s generation assets, any above market purchased power costs, and any
    deferred debit related to a utility=s discontinuance of the application of Statement
    of Financial Accounting Standards No. 71 [i.e., unrecovered regulatory assets].
    Tex. Util. Code Ann. ' 39.251(7). PURA further defines generation assets as follows:
    statutory authority. City Pub. Serv. Bd. v. Public Util. Comm=n, No. 3-00-007-CV, slip op. at 8,
    2002 Tex. App. LEXIS 2059, at *12 (Tex. App. AustinCMar. 21, 2002, no pet.). (AIn order to be
    invalid, the 1999 Rule must, on its face, contravene the legislative grant of power.@)
    15
    AGeneration assets@ means all assets associated with the production of electricity,
    including generation plants, electrical interconnections of the generation plant to
    the transmission system, fuel contracts, fuel transportation contracts, water
    contracts, lands, surface or subsurface water rights, emissions -related allowances,
    and gas pipeline interconnections.
    
    Id. ' 39.251(3).
    As described above, at the true -up proceeding, the Commission is required to
    calculate a utility=s actual stranded costs by subtracting the market value of its generation assets
    from their book value. If this number is negative, i.e., if the market value of those assets exceed
    their book value, it is undisputed that the utilities are not required to refund this negative amount
    to the ratepayers. Under chapter thirty-nine, there is simply no concept of negative stranded
    costs and no consequence of a negative calculation.
    Chapter thirty-nine defines stranded costs as Athe positive excess of net book
    value of generation assets over the market value of the assets.@ See 
    id. ' 39.252(7)
    (emphasis
    added). Because we presume that each word in a statute has meaning, the word Apositive@ must
    be given effect. See Southwestern Life Ins. Co. v. Montemayor, 
    24 S.W.3d 581
    , 584 (Tex.
    App.CAustin 2000, pet. denied). Stranded costs therefore exist only when the book value of a
    utility=s generation assets exceeds their market value. If book value is equal to or less than
    market value, then there are no stranded costs. The term Anegative stranded costs@ appears
    nowhere in chapter thirty-nine, and there are no statutory provisions providing for recovery by
    ratepayers of the excess market value over cost.
    16
    The fact that chapter thirty-nine does not recognize the concept of negative
    stranded costs motivates the Commission=s argument that all the true -up items represent
    stranded costs and that the netting required under its rule will determine actual stranded costs.
    The utilities protest that the other true -up items do not comprise stranded costs as they are
    defined in chapter thirty-nine and cannot be offset by a negative stranded-cost calculation. They
    focus particularly on showing that the final-fuel balance has nothing to do with stranded costs.
    The Commission responds by arguing that because coal, gas, nuclear, and other types of fuel are
    Aindisputably assets associated with the production of electricity,@ they constitute generation
    assets that could become stranded. We reject the Commission=s attempt to define these items as
    stranded costs.
    Under the prior regulatory regime, the approved rates for a utility always included
    a Afixed fuel factor,@ which was based on a projection of future fuel costs. 16 Tex. Admin. Code
    ' 25.237 (2002). The Commission periodically adjusted this fuel factor, and at least every three
    years the fuel revenues the utility received under the factor were Areconciled@ with the fuel costs
    the utility actually incurred. See Tex. Util. Code ' 36.203 (West 1998); 16 Tex. Admin. Code '
    25.236 (2002); see also Nucor Steel v. Pub. Util. Comm=n, 
    26 S.W.3d 742
    , 744-45 (Tex.
    App.CAustin 2001, pet. denied). Chapter thirty-nine, section 36.202(c) simply postpones the fuel
    reconciliation for the final period of regulation until the 2004 true -up proceeding, at which time
    any under-recovered fuel balances will be surcharged.
    17
    The statutory structure of chapter thirty-nine also indicates that the legislature did
    not consider a final fuel balance to be a stranded cost. Stranded costs and the final fuel balance
    are determined and recovered under separate sections of chapter thirty-nine.
    Stranded costs are determined and recovered under sections 39.201(l) and
    39.262(c). Section 39.201(l) provides: A[t]wo years after customer choice is introduced, the
    stranded cost estimate under this section [i.e., the stage-two stranded-cost estimate] shall be
    reviewed and, if necessary, adjusted to reflect a final, actual valuation in the true-up proceeding
    under Section 39.262.@ Tex. Util. Code Ann. ' 39.201(l). Section 39.262(c) provides:
    After January 10, 2004 . . . each transmission and distribution utility, its affiliated
    retail electric provider, and its affiliated power generation company shall jointly
    file to finalize stranded costs under Subsections (h) and (i) and reconcile those
    costs with the estimated stranded costs used to develop the competition transition
    charge in the proceeding held under Section 39.201.
    
    Id. ' 39.262(c).
    Subsections (h) and (i) set out methods for quantifying the market value of a
    utility=s generation assets and calculating its stranded costs. Significantly, the final fuel balance
    does not figure into this calculation.
    Under-recovered fuel costs are determined and recovered under section 39.202(c)
    and 39.262(d)(1). Section 39.202(c) provides: A[a]fter the date of customer choice, each affiliated
    power generation company shall file a final fuel reconciliation for the period ending the day before
    the date customer choice is introduced . . . [which will be] included in the true -up proceeding.@ 
    Id. ' 39.202(c).
    Section 39.262(d)(1) provides Athe affiliated power generation company shall
    18
    reconcile, and either credit or bill to the transmission and distribution utility, the net sum of . . .
    the former electric utility=s final fuel balance . . . and [the capacity-auction true-up amount].@ 
    Id. ' 39.262(c).
    Stranded costs and the final fuel balance are distinct concepts treated separately in
    the statute. If the legislature wanted to define an under-recovered fuel balance as a stranded cost
    it could have done so explicitly, or it could have easily included the impact of the final fuel
    reconciliation in the market valuation of a utility=s generation assets under section 39.262(c), (h),
    and (i). The fact that the legislature treated the fuel balance separately shows that it did not
    intend it to be a component of a stranded-cost calculation.
    The same is true of the other true -up items. The capacity-auction true-up amount
    is the difference between the price the utility, or its unbundled power generation affiliate, was
    estimated to obtain for its power on the wholesale market in the second stage of stranded-cost
    recovery and the price the utility actually received during the first two years of competition.
    Although there is a closer nexus between this true -up item and the final determination of stranded
    costs, the legislature chose not to include this item in its definition of stranded costs or to
    incorporate it into the methods it prescribes for calculating stranded costs. Moreover, the
    legislature specifically mandated that this item be netted with the final fuel balance. 
    Id. ' 39.262(d).
    Chapter thirty-nine seems to contemplate two parallel true -up tracksCone for
    stranded costs and one for the several other true -up items. Separate portions of chapter thirty-
    19
    nine govern the effects that the calculations under each track are to have on rates. Compare 
    id. ' 39.262(c),
    with 
    id. ' 39.262(g).
    Although the calculation under each track can be applied to
    adjust the transmission and distribution utility=s nonbypassable rates, the utilities are authorized
    to securitize any remaining stranded costs but not positive balances associated with the other
    true-up items.    Id ' 39.262(c). In some circumstances, performing two parallel true -up
    calculations, as the statute provides, and performing a single true -up calculation that nets
    stranded costs against all the true -up items, as the rule requires, would result in identical
    adjustments to rates. However, netting the stranded-cost calculation with the other true -up items
    can cause an impermissible offset of amounts due a utility whenever the market value of its
    generation assets exceed their book value, i.e., when it has no stranded costs. See generally 
    id. '' 39.252(a)
    (a utility is allowed to recover all its net verifiable stranded costs), .262(c)-(i)
    (contemplating two parallel true-up tracks).
    We thus reject the Commission=s argument that the other true -up items represent
    stranded costs. We agree with the utilities that the statute does not contemplate a negative
    stranded-cost calculation and does not contemplate any consequence to ratepayers if the
    stranded-cost calculation produces a negative number. The rule that would net a negative
    stranded-cost calculation against a positive balance produced from the other true-up items is not
    authorized by the statute. Indeed, it directly contradicts the legislature =s intent that a positive
    stranded-cost calculation has significance while a negative calculation simply means that a utility
    is not entitled to recovery of stranded costs. By collapsing two parallel true -up tracks into a
    20
    combined calculation, the rule impermissibly allows a negative stranded-cost calculation to offset
    positive balances due from other true -up items. The statute does not require a utility to refund a
    negative calculation of stranded costs to ratepayers and the Commission may not require such a
    refund by calling these other true -up items stranded costs.
    Reversing Securitization Over-Recoveries
    We now turn to the Commission=s claim that even so, netting the calculations is a
    permissible means of preventing over-recovery of stranded costs by those utilities that received a
    windfall through securitization. When the legislature provided for mitigation and securitization of
    estimated stranded costs, it did so with the proviso that the Commission must ensure that no
    utility over-recover its stranded costs. See 
    id. ' 39.262(a).
    The utilities that were estimated in
    the first stage to have stranded costs received substantial sums of money or its equivalent
    through mitigation and securitization proceeds. When the revised stranded-cost estimate showed
    that these utilities were likely to have no stranded costs, the Commission required the utilities to
    disgorge their mitigation proceeds through excess mitigation credits. As previously noted,
    however, the Commission could not reverse the transition charge imposed on ratepayers to
    finance the bonds that the utilities had sold. See 
    id. '' 39.201(l)(1),
    .303(d).
    When the legislature expressly confers a power on an agency, it also impliedly
    intends that the agency have whatever powers are reasonably necessary to fulfill its express
    functions or duties. Public Util. 
    Comm=n, 53 S.W.3d at 316
    . Chapter thirty-nine requires the
    Commission to see that utilities do not over-recover their stranded costs. The Commission argues
    21
    that netting the various true -up items is a permissible way to prevent over-recoveryCeffectively
    forcing the utilities that sold transition bonds based on earlier invalid stranded-cost estimates to
    disgorge amounts to which they are not entitled.
    While we agree with the Commission that it has the implied power to attempt to
    reverse over-recovery of stranded costs through netting, we find its rule to be overbroad. An
    agency may not exercise what is effectively a new power on the theory that such exercise is
    expedient for the agency=s purposes.         GTE-Southwest, 
    Inc., 901 S.W.2d at 407
    .           The
    Commission=s rule does not limit the amount by which a negative stranded-cost calculation can
    offset other positive true -up balances to a utility=s previous over-recovery. See 16 Tex. Admin.
    Code. ' 25.263(l). We hold that the Commission has the discretion to net a negative stranded-
    cost calculation against the other true -up items only to the extent that the utility over-recovered
    stranded costs through securitization.
    For example, a utility that entered the first stage of stranded-cost recovery with
    generation assets having a book value of 3x and an estimated market value of 1x would have
    been required to mitigate or securitize estimated stranded costs of 2x. Assume that this utility
    sold transition bonds and removed 2x from its books, reducing its book value to 1x. If the market
    value of this utility=s generation assets has risen to 3x at the time of the true -up proceeding, the
    updated stranded-cost calculation will yield a negative 2x indicating that it has no actual stranded
    costs. But to the extent the book value was reduced by the proceeds of securitization, the utility
    appears to have over-recovered 2x when it received its bond proceeds. This is true because the
    22
    original book value of 3x would not have exceeded the increased market value of 3x, even had
    the utility never received bond proceeds of 2x. The full 2x would represent an over-recovery of
    stranded costs that the utility did not have. This amount, but no more, may be netted against
    other sums to prevent over-recovery.
    The Commission must conduct parallel true-up calculations for strandedcosts and
    the other true-up items. Only in those limited circumstances where a negative calculation of
    stranded costs results from the reduction of book value by securitization may the Commission
    devise a rule to offset any windfall received through securitization against the positive balance
    due the utility for the other true -up items. If a utility=s stranded-cost calculation would have been
    negative even if it had never sold transition bonds, then the full amount of its bond proceeds
    represents an over-recovery which can be netted against the other true -up items. On the other
    hand, if a utility would have had a positive stranded-cost calculation but for the fact that it sold the
    bonds, i.e., if it would be entitled to recover stranded costs had it never reduced its book value
    through securitization, the Commission is limited to netting the amount by which the bond
    proceeds exceeded the actual stranded costs it would have recovered. 12
    12
    The exact changes that the Commission makes to its rule to bring it into compliance
    with these principals are, of course, matters of discretion. The Commission could simply add a
    safety-valve provision which, for any utility, limits the amount by which a negative stranded-cost
    23
    calculation can offset other positive true -up balances to permissible amounts. Determining these
    permissible amounts at the true -up proceeding would not be difficult because it merely requires
    hypothetical adjustments to book value based on known information.
    24
    Reliant argues that it should not be required to disgorge any over-recovery it may have
    received through securitization. Its basic complaint seems to be that the Commission=s rule does not
    account for the fact that securitization substantially reduces the book value of a utility=s generation assets.
    We believe that our formulationCrequiring the Commission to consider what a utility=s stranded-cost
    calculation would have been absent securitizationCaddresses this concern. 13
    13
    Reliant claims that failure to take this reduction of book value into account causes the
    Commission to inaccurately catagorize the bond proceeds as an over-recovery. Reliant also argues that by
    netting the amounts that a utility received when it sold securitization bonds against other amounts it is due,
    the Commission accomplishes indirectly what it is directly prohibited from doing by statute. This argument is
    misconceived. Chapter thirty-nine makes securitization financing orders irrevocable and prohibits the
    Commission from adjusting the transition charges in order to assure payment to bondholders and allow the
    bonds to be issued on more favorable terms. See Tex. Util. Code. Ann. '' 39.301, .304, .306, .307
    (West Supp. 2003). Transition charges flow to the bondholders to retire the transition bonds by paying all
    the principal and interest. See id.; City of Corpus 
    Christi, 51 S.W.3d at 239
    . Nothing in chapter thirty-
    nine guarantees that a utility can keep bond proceeds to which it is not entitled.
    25
    In no circumstances may a negative stranded-cost calculation attributable to
    market conditions be netted against a positive fuel balance or other such true -up calculation. We
    sustain the challenge to the rule because it does not limit the netting of negative stranded-cost
    calculations to prevent over-recovery attributable to securitization. The Commission has the
    statutory authority to prevent over-recovery of stranded costs through securitization. It has no
    statutory authority to net negative stranded costs attributable to market forces.14
    14
    In view of our disposition of this issue, we need not address the utilities= equal-
    protection arguments. See Tex. R. App. P. 47.1 (opinions must be as brief as practicable).
    Similarly, we do not specifically reference the arguments of the several intervenors on this issue
    because they do not differ materially from those of the Commission. See 
    id. Throughout our
    opinion, we discuss the arguments of the intervenors only when they differ materially from those
    of the Commission.
    26
    Partial Stock Valuation Method
    One of the Commission=s most important responsibilities during the true -up
    proceeding is to calculate the market value of a utility=s generation assets. See generally Tex.
    Util. Code Ann. ' 39.262(h). Chapter thirty-nine sets out several different methods that the
    Commission may use to make this calculation. See 
    id. The utilities
    claim that the Commission
    exceeded its authority in promulgating portions of its rule that implement Athe partial stock
    valuation method.@ See generally 
    id. ' 39.262(h)(3);
    16 Tex. Admin. Code ' 25.263(f)(1)(C)
    (2002).
    The Commission is authorized to use the partial stock valuation method to
    establish the value of generation assets when a utility has transferred some or all of those assets
    to affiliated or nonaffiliated corporations and between nineteen and fifty-one percent of the
    common stock of each such corporation is spun off and sold to public investors through a national
    stock exchange and traded for one year or more. See Tex. Util. Code Ann. ' 39.262(h)(3). The
    Commission is authorized to calculate the value of the assets held by the transferee corporation,
    presumably an unbundled power generation company, by adding the market value of its common
    stock to the book value of its preferred stock and its debt. See id.; see generally 16 Tex. Admin.
    Code ' 25.263(f)(1)(C)(viii).
    A. Control Premium
    The average daily closing price over thirty consecutive trading days, chosen by the
    Commission, with some constraints, is generally presumed to establish the market value of the
    27
    common stock. See Tex. Util. Code Ann. ' 39.262(h)(3). The Commission, however, is also
    authorized to convene a panel of financial experts to determine whether a control premium exists
    for the retained common stock. 
    Id. A control
    premium is the additional value that a block of
    shares obtains by virtue of the fact that it carries with it the power to control the corporation. See
    Black=s Law Dictionary 1200 (7th ed. 1999). AThe control premium is often computed by
    comparing the aggregate value of the controlling block of shares with the cost that would be
    incurred if the shares could be acquired at the going market price per share.@ 
    Id. The utilities
    challenge the way that the control premium is calculated under the
    Commission=s rule.
    Section 39.262(h)(3) of PURA specifically provides:
    The [C]ommission may accept the market valuation to conclusively establish the
    value of the common stock equity in each transferee corporation or convene a
    valuation panel of three independent financial experts to determine whether the
    percentage of common stock sold is fairly representative of the total common
    stock equity or whether a control premium exists for the retained interest. . . . If
    the panel determines that a control premium exists for the retained interest, the
    panel shall determine the amount of the control premium, and the [C]ommission
    shall adopt the determination but may not increase the market value by a control
    premium greater than 10 percent.
    Tex. Util. Code Ann. ' 39.262(h)(3) (emphasis added). The Commission=s rule, however,
    provides:
    If the panel determines that a control premium exists for the retained interest, the
    panel shall determine the amount of the control premium, and the [C]ommission
    shall adopt the determination, but may not use the control premium to increase the
    value of the assets by more than 10%.
    28
    16 Tex. Admin. Code ' 25.263(f)(1)(C)(v) (emphasis added). The utilities argue that the statute
    only allows the Commission to apply the control premium to increase the value of the retained
    common stock equity by up to ten percent. They claim that the rule is invalid because it instead
    allows the Commission to apply the control premium to increase by up to ten percent the value of
    all the corporation=s assets.15 The Commission responds that while the statute prohibits it from
    Aincreas[ing] the market value by a control premium greater than 10 percent,@ see Tex. Util. Code
    Ann. ' 39.262(h)(3), the statute does not specify A[ten] percent@ of what and that we should defer to its
    interpretation.
    We may not add words to a statute unless necessary to give effect to legislative intent.
    Southwestern Life 
    Ins., 24 S.W.3d at 583
    . The Commission essentially asks us to add the words Aof all
    the corporation=s assets@ to the end of the statutory phrase Aby a control premium no greater than 10
    percent.@ But the meaning of the phrase is unmistakable without such an addition. Because a control
    premium represents value added to a retained block of shares, a Acontrol premium of ten percent@ would
    naturally increase the value of the retained block of shares by ten percent. Similarly the phrase Aby a control
    premium no greater than 10 percent@ is limited to increasing the value of the retained block of shares by no
    15
    As explained above, under the partial stock valuation method a corporation=s common
    stock represents only a portion of the total value of its assets. See Tex. Util. Code Ann.
    ' 39.262(h)(3); 16 Tex. Admin. Code ' 25.263(f)(1)(C). Of course, the retained portion of that
    stock represents an even smaller portion of the total value of its assets. See 
    id. 29 more
    than ten percent. We agree with the utilities that the Commission exceeded its authority by enacting
    the portion of its rule that would apply the control-premium cap to all of the corporation=s assets.
    B. AOther Admitted Evidence@
    Reliant also complains that the rule impermissibly allows the Commission to second-guess
    the findings of the valuation panel. Chapter thirty-nine, section 39.262(h)(3) requires a valuation panel
    consisting of three financial experts chosen from the top ten nationally recognized investment
    banks with demonstrated experience in the electric industry of the United States. Tex. Util. Code
    Ann. ' 39.262(h)(3). It then provides, A[i]f the panel determines that a control premium exists for
    the retained interest, the panel shall determine the amount of the control premium, and the
    commission shall adopt the determination [subject to the ten-percent cap].@ 
    Id. (emphasis added).
    The statute further provides that Athe determination of the commission based on the
    finding of the panel conclusively establishes the value of the common stock in each transferee
    corporation.@ 
    Id. Rule 25.263,
    however, states that the Commission is to determine the value of
    the common stock of the transferee corporation Abased on the findings of the Commission and
    other admitted evidence.@ See 16 Tex. Admin. Code 25.263(f)(1)(C)(vii) (2002) (emphasis added).
    The Commission argues that the language Aother admitted evidence@ was intended
    only to allow for consideration of evidence relating to issues other than the panel=s substantive
    finding, such as the Commission=s obligation to reduce any control premium by ten percent, or to
    ensure that the panel was properly constituted in accordance with the statute. See Tex. Util. Code
    30
    Ann. ' 39.262(h)(3). It claims that if the rule is applied in a way that fails to respect the panel=s
    determination, the proper place to challenge it is at the true -up proceeding.
    By requiring that the Commission Ashall adopt@ the panel=s control-premium
    determination, the legislature signaled its intent that the valuation of the panel be conclusive.
    The extra-statutory language of the rule, as written, allows the Commission to consider whatever
    evidence it chooses to increase the value of the common stock. The Commission cannot simply
    confer this authority on itself without legislative approval. See Ford Motor Co. v. Motor Vehicle
    Bd. 
    21 S.W.3d 744
    , 764 (Tex. App.CAustin 2000, pet. denied) (an agency Amay not, on a theory
    of necessary implication from a specific power, function, or duty expressly delegated, erect and
    exercise a new or additional power or a power that contradicts the statute@).
    The Commission is also wrong to contend that Reliant=s complaint is not properly
    brought as a validity challenge. It cannot promulgate a rule granting to itself a power in
    contradiction of its legislative mandate, and then claim that because it intends to interpret the rule
    narrowly that the issue is somehow one of application and not validity. We sustain the challenge
    to this portion of the rule.16
    16
    Intervenors TIEC, SCC, and OPUC argue that the challenged portion of the rule is
    valid because the Commission can choose not to convene a valuation panel at all, in which case it
    must consider Aother admitted evidence@ in order to determine market value. They argue that, in
    light of this discretion, the statutory requirement that the Commission=s determination be Abased
    on the finding of the panel@ means only that the panel=s determination is to provide a basis, but
    not necessarily the sole basis, for the Commission=s interpretation. We disagree. The challenged
    portion of the rule only applies if the Commission chooses to convene a valuation panel.
    Moreover, the statute is clear that when a panel is convened, its determination is to be
    conclusive. See Tex. Util. Code. Ann. ' 39.262(h)(3). On the intervenors = interpretation, the
    31
    Interest
    A utility found to have stranded costs at the true -up proceeding must either
    securitize those costs or recover them over time through nonbypassable rates. See Tex. Util.
    Code Ann. ' 39.262(c); 16 Tex. Admin. Code ' 25.263(l)(2)(A) (2002). For a utility that does not
    securitize its stranded costs, full recovery may take a number of years. Rule 25.263 provides that
    if a utility is found to have stranded costs at the true -up proceeding, then its unbundled
    transmission and distribution affiliate Ashall be allowed to recover . . . carrying costs [i.e., interest]
    on the true-up balance.@ See 16 Tex. Admin. Code ' 25.263(l)(3) (2002). Because of the time
    value of money, this interest represents a portion of the Anet, verifiable, nonmitigable stranded
    costs@ that the utility is entitled to recover under chapter thirty-nine. See generally Tex. Util.
    Code Ann. ' 39.252(a). The rule further provides that interest shall be calculated from the date
    that the final true-up order is issued until stranded costs are fully recovered. See 16 Tex. Admin.
    Code ' 25.263(l)(3).
    requirement that the Commission=s determination be Abased on the findings of the panel@ would
    be superfluous given the fact that it follows a requirement that the Commission Ashall adopt@ the
    panel=s determination. See Texas Workers= Compensation Ins. Fund v. Del Industrial, Inc., 35
    S.W.3d. 591, 593 (Tex. 2000) (AA cardinal rule of statutory construction is that each sentence,
    clause and word is to be given effect if reasonable and possible.@).
    32
    The utilities argue that the rule=s provision for interest is deficient. The y claim that
    interest should be calculated to accrue from January 1, 2002, the first day of competition, because
    this is when costs became Astranded.@ The Commission rejoins that stranded costs do not
    magically arise on the first day of competition, but, for purposes of stranded-cost recovery under
    chapter thirty-nine, come into existence only after the true -up proceeding. We agree with the
    Commission.
    The true-up proceeding determines whether a utility has any actual stranded costs.
    See Tex. Util. Code Ann. ' 39.201(l), .262(c). At that time, the Commission is to determine a
    utility=s stranded costs by comparing the market value of the utility=s generation assets with their
    book value. The utilities attach some significance to the fact that the stranded-cost calculation is
    to use the book value of December 31, 2001Cthe last day of regulation. See Tex. Util. Code Ann.
    ' 39.251(7). They contend that this indicates that the true -up proceeding actually determines the
    amount of stranded costs that existed on the first day of competition. This contention is false.
    While the book value to be used by the Commission at the true -up proceeding is to be determined
    as of December 31, 2001, its calculations are to be based on the market value as determined in
    the proceeding. See 
    id. ' 39.262(h).
    This market value may fluctuate widely between the first
    day of competition and the date of the true -up proceeding. Moreover, a formerly regulated utility
    enters the first day of competition with its preexisting customer base intact, i.e., the utility=s
    affiliated retail electric provider inherits the retail customers in the former utility=s service area.
    33
    In the first few years of competitionCbefore the 2004 true -up proceedingCa utility can take steps
    to increase the market value of its generation assets by simply participating in the market.17
    That the legislature chose the last day of regulation as the day for measuring book
    value is inconsequential. After competition is introduced, a utility no longer accrues Abook
    value,@ because such a concept is meaningless outside of the former regulatory system. We
    reject the utilities= argument that their actual stranded costs all accrued on the first day of
    competition.
    17
    For example a utility may upgrade a plant or successfully renegotiate an above-cost fuel contract.
    Cf. Tex. Util. Code Ann. ' 39.251(7) (requiring that Aabove market purchased power costs@ be
    considered in any stranded-cost calculation).
    34
    Reliant makes an additional argument that interest on at least a portion of its
    recoverable stranded costs should accrue from the first day of competition. It claims that A[t]o
    the extent Reliant . . . has stranded costs in 2004, the Commission=s 2001 stranded-cost estimates
    [which resulted in reversal of Reliant=s earlier mitigation efforts] will have been incorrect@ and
    Reliant will have been deprived of the opportunity to recover its stranded costs through early
    mitigation. See generally Tex. Util. Code Ann. '' 39.201(d)-(l), .254, .256. It therefore contends
    that interest on any stranded costs attributable to reversed mitigation should accrue from the time
    that it is required to issue excess mitigation credits. This argument lacks merit. The duty to
    utilize the statute=s mitigation procedures was predicated on stranded-cost estimates, see 
    id., and a
    utility=s right to fully recover its stranded costs does not encompass a right to early mitigation. 18
    See 
    id. 39.252(a). AEP
    also argues that providing for interest to accrue only from the date of the final
    order is arbitrary and capricious because orders affecting different utilities will likely be issued on
    different dates. This argument also lacks merit. Normal Aregulatory lag@ is considered to be an
    element of risk borne by a utility. See State v. Public Util. Comm=n, 883 S.W.2d. 190, 196 (Tex.
    1994). The utilities therefore are not entitled to revenues lost due to the time it takes to conduct
    the true-up proceeding.
    18
    We also reject Reliant=s claim that interest on the capacity auction true-up amount should accrue
    from the first day of competition. We have held that the capacity auction true-up amount is not a
    component of stranded costs.
    35
    We overrule the utilities= issues challenging section 25.236(l)(3) of the
    Commission=s competition rule and hold that the Commission=s provision for interest is adequate
    to provide the utilities with full recovery of their stranded costs.
    Failure to Reduce Potential Stranded Costs
    Because recoverable stranded costs are determined according to the market value of
    generation assets as measured in the 2004 true-up proceeding, any move that increases the market value of
    these assets before the true-up proceeding will potentially reduce a utility=s stranded-cost recovery. For
    utilities with significant unrecovered book value there will be no competitive-market incentive to maintain or
    increase the market value of their assets until after the true-up proceeding.
    Chapter thirty-nine addresses this lack of market incentive by creating a statutory incentive.
    It provides that utilities are only allowed to recover stranded costs that are Anonmitigable,@ see Tex. Util.
    Code Ann. ' 39.252(a), and requires Aan electric utility . . . [to] pursue commercially reasonable means to
    reduce its potential stranded costs, including good faith attempts to renegotiate above-cost fuel and
    purchased power contracts or the exercise of normal business practices to protect the value of its assets.@
    See 
    id. ' 39.252(d).
    To enforce this requirement the legislature mandated that Athe [C]ommission shall
    consider the utility=s efforts under this subsection when determining the amount of the utility=s stranded costs;
    provided, however, that nothing in this section authorizes the [C]ommission to substitute its judgment for a
    market valuation of generation assets determined under Sections 39.262(h) and (i).@ 
    Id. Rule 25.263(e)(4)
    implements this section. It provides that the Commission will determine
    at the true-up proceeding whether the utility, through its unbundled successor affiliates, has pursued
    36
    commercially reasonable means to reduce its stranded costs. It further provides that if the [C]ommission
    finds that a utility=s successor affiliates Ahave failed, individually or in combination, to fully comply with their
    obligations under PURA ' 39.252(d), the [C]ommission may reduce the net book value of the . . .
    [affiliated power generation company=s] generation assets or take other measures it deems appropriate in
    the true-up proceeding filed under this section.@ See 16 Tex. Admin. Code ' 25.263(e)(4) (2002).
    AEP and Reliant each challenge this portion of the rule, but on different grounds. AEP
    claims that a utility=s duty to reduce its potential stranded costs ended once it unbundled into successor
    affiliates, while Reliant argues that the Commission lacks the authority to reduce the book value of
    generation assets. We reject both arguments.
    AEP claims that unbundled power generation companies and retail electric providers are not
    required to reduce their potential stranded costs. It argues that these successor affiliates have no such duty
    because section 39.252(d) imposes the duty on A[a]n electric utility@ and PURA=s general definition of
    electric utility specifically excludes power generation companies and retail electric providers. See Tex. Util.
    Code Ann. ' 31.002(6). This argument cannot survive close scrutiny because it requires us to construe
    portions of the statute in isolation and would lead to absurd results. See Southwestern Life 
    Ins., 24 S.W.3d at 583
    -85.
    Section 39.252(a) grants the right to recover stranded costs to Aan electric utility.@ Tex. Util.
    Code Ann. ' 39.252(a). Section 39.252(d) imposes the duty to pursue commercially reasonable means to
    reduce potential stranded costs on Aan electric utility,@ and requires the commission to consider Athe utility=s@
    efforts when determining the amount of stranded costs, i.e., when conducting the true-up proceeding. 
    Id. ' 37
    39.252(d). These subsections all affect the stranded-cost calculation to take place at the true-up
    proceeding. Yet at the true-up proceeding, Aan electric utility@ is to collect its stranded costs through its
    successor affiliates. See 
    id. ' 39.262(c)
    (A. . . each transmission and distribution utility, its affiliated retail
    electric provider, and its affiliated power generation company shall jointly file to finalize stranded costs . . .
    .@). The Aelectric utility=s@ stranded costs are calculated according to the market value of the generation
    assets owned by its successor power generation company. See 
    id. ' 39.262(h),
    (i). It is apparent from
    these sections that when the legislature was discussing stranded-cost recovery it sometimes used the term
    Aelectric utility@ to refer to an integrated utility=s successor affiliates.
    Moreover, AEP=s reading would lead to absurd results. As discussed above, section
    39.252(d) imposes on an electric utility the statutory duty to try to reduce stranded costs as a substitute for
    market incentive. As discussed above, until the true-up proceeding, no utility with significant book value will
    have any market incentive to increase or maintain the value of its generation assets because any move to do
    so will correspondingly reduce its stranded-cost recovery. The unbundling of a utility into successor
    affiliates does not affect this lack of incentive. We decline to attribute to the legislature the intent to make
    such an arbitrary distinction.
    Reliant attacks the rule on another basis. The rule allows the Commission to reduce the
    book value of a utility=s generation assets if its successor affiliates have not pursued commercially reasonable
    means to reduce potential stranded costs. See 16 Tex. Admin. Code ' 25.263(e)(4) (2002). According to
    Reliant, the legislature=s Aobvious purpose@ in prohibiting the Commission from substituting its judgment for
    the market valuation of generation assets is to ensure that the true-up calculation yields an accurate
    38
    stranded-cost number. Reliant argues that by allowing the Commission to adjust book value, the rule
    circumvents the statutory goal of calculating an accurate stranded-cost amount. We disagree.
    We note initially that the relevant statutory goal is not calculating an accurate stranded-cost
    amount, but calculating an accurate Averifiable, non-mitigable stranded cost[]@ amount. Tex. Util. Code
    Ann. ' 39.252(a) (emphasis added). Compliance with the duty to pursue commercially reasonable means
    to mitigate its potential stranded costs is part of what makes stranded costs non-mitigable. See 
    id. ' 39.252(a),
    (d). Reliant=s interpretation is likely to yield inaccurate determinations of non-mitigable stranded
    costs.
    Nothing in the statute explicitly prohibits the Commission from reducing a utility=s book
    value if it finds that it or its successor affiliates have failed to comply with their obligation to attempt to
    reduce stranded costs. In fact, the statute implies that just such an adjustment should take place. As noted,
    section 39.252, subsection (d) requires the Commission to consider a utility=s attempts to comply with this
    obligation when determining a utility=s stranded costs at the true-up proceeding. See 
    id. ' 39.252(d).
    Because this same subsection further provides that the Commission is prohibited from adjusting the market
    value of the generation assets as determined under section 39.262(h) and (i), see id, it impliedly
    contemplates some sort of adjustment to book valueCthe only other component of stranded costs. We
    overrule the utilities= challenge to section 25.263(e)(4) of the Commission=s rule.
    CONCLUSION
    The Commission erred in promulgating that portion of its rule which unqualifiedly allows a
    negative stranded-cost calculation to offset other amounts a utility may become entitled to at the true-up
    39
    proceeding. The statutory duty to see that a utility does not over-recover its stranded costs justifies netting
    a negative stranded-cost number against the other true-up amounts only to the extent that it reverses an
    actual over-recovery due to securitization. The Commission also erred in promulgating those portions of its
    rule which, in setting out the partial stock valuation method, (1) allow it to apply the ten-percent control-
    premium cap to the value of all corporate assets, and (2) allow it to second-guess the valuation of the panel
    by considering other admitted evidence. We reverse these portions of the rule and remand them to the
    Commission for further proceedings consistent with this opinion. We find the other challenged portions of
    the rule to be valid and uphold them as enacted.
    ON REHEARING
    The utilities filed motions for rehearing asking that we clarify certain portions of our opinion
    and substantively change other portions. We grant the motions for purposes of clarification only and
    substitute modified pages. We overrule the motions insofar as they request that we change our holding.
    Our opinion and holding remain substantively unchanged.
    Bea Ann Smith, Justice
    Before Justices Kidd, B. A. Smith and Yeakel
    Affirmed in Part; Reversed and Remanded in Part
    Filed: February 6, 2003
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