NIPSCO Industrial Group v. Northern Indiana Public Service Company, and Office of the Utility Consumer Counselor , 125 N.E.3d 617 ( 2019 )


Menu:
  •                                                                        FILED
    Jun 27 2019, 4:11 pm
    CLERK
    Indiana Supreme Court
    Court of Appeals
    and Tax Court
    IN THE
    Indiana Supreme Court
    Supreme Court Case No. 18S-EX-475
    NIPSCO Industrial Group,
    Appellant (Intervenor below),
    –v–
    Northern Indiana Public Service Company,
    Appellee (Petitioner below),
    and
    Office of the Utility Consumer Counselor,
    Appellee (Statutory Party below).
    Argued: November 1, 2018 | Decided: June 27, 2019
    Appeal from the Indiana Utility Regulatory Commission
    No. 44733-TDSIC-2
    On Petition to Transfer from the Indiana Court of Appeals
    No. 93A02-1711-EX-2735
    Opinion by Justice Goff
    Chief Justice Rush and Justice Massa concur.
    Justice Slaughter dissents with separate opinion in which Justice David joins.
    Goff, Justice.
    Everyone reaps a benefit when utilities are allowed to plan for
    investments in necessary and reasonable infrastructure projects. The
    “TDSIC Statute” at issue in this appeal promotes this beneficial behavior
    through a complex, integrated process that aims to protect all sides
    involved. On the utilities’ side, the statute allows utilities to seek pre-
    approval from the Indiana Utility Regulatory Commission for certain
    electric or gas infrastructure projects and to recoup the costs of those
    projects through periodic petitions to the Commission for increases to its
    rates. On the consumers’ side, the statute requires the Commission to
    make determinations regarding the public convenience, necessity, and
    reasonableness of planned projects before approving a plan to complete
    them. This process protects both suppliers and consumers of electric and
    gas services, improves the stability of the provision of these services, and
    increases the predictability of costs associated with providing and using
    these services.
    Here, the process started off well but eventually broke down. The
    parties to this appeal agreed to two expansive, multi-year settlements
    regarding rates and infrastructure investments under the TDSIC Statute,
    and they asked the Commission to approve the agreements, which it did.
    These agreements specified how, in the utility’s periodic petitions to the
    Commission, rate increases should be calculated and allocated among the
    utility’s various rate classes. Despite being a party to the underlying
    agreements, a group of some of the utility’s largest industrial customers
    opposed the utility’s second periodic petition, arguing that the utility’s
    rate calculation and allocation based on the underlying agreements was
    contrary to the TDSIC Statute. The Commission rejected this argument,
    and the customer group sought judicial review.
    This case, at its core, involves a party to and proponent of two complex
    administrative settlement agreements raising a challenge to specific parts
    of those settlements in a later proceeding. Concluding that the customer
    group is estopped from raising this delayed challenge and further
    concluding that the Commission’s order contains sufficient findings, we
    affirm the Commission.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019         Page 2 of 18
    Factual and Procedural History
    Given the lengthy and interwoven background of this appeal, our
    discussion of the factual and procedural history proceeds in three parts.
    We begin with a summary of some of the ways in which the Indiana
    Utility Regulatory Commission regulates utility rates and an overview of
    the specific challenge to the regulatory activity raised here. Then, we
    discuss two large-scale regulatory proceedings that provide the basis for
    the proceeding below. We conclude with a summary of the proceedings
    before the Commission and the Court of Appeals below.
    I.    Regulation of utility rates generally and the
    specific challenge to the rate regulation here
    Last year, in litigation between some of the same parties involved in
    this appeal, we discussed the general processes by which utility rates are
    set and adjusted. See NIPSCO Indus. Grp. v. N. Ind. Pub. Serv. Co. (NIPSCO
    2018), 
    100 N.E.3d 234
    , 238–39 (Ind. 2018), modified on reh’g. We find a brief
    summary of these processes helpful in placing this appeal in the proper
    context.
    Base utility rates are traditionally set or adjusted through a general
    ratemaking case (variously referred to as a general rate case or base rate
    case) before the Commission. This is a comprehensive process in which
    the Commission “examine[s] every aspect of the utility’s operations and
    the economic environment in which the utility functions . . . .” 
    Id. at 238
    (quoting U.S. Gypsum, Inc. v. Ind. Gas Co., 
    735 N.E.2d 790
    , 798 (Ind. 2000)).
    Such a detailed review allows the Commission to ensure that utility rates
    are fair to both the utility and its customers. 
    Id. In addition
    to the comprehensive process of a base rate case, utility
    rates can be adjusted to reflect specific projects and costs through a
    “tracker” or “rider” procedure before the Commission. The TDSIC
    Statute, at issue in this appeal, provides one such proceeding related to
    electric or gas transmission, distribution, and storage system
    improvement charges a public utility imposes for certain improvement
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019         Page 3 of 18
    projects. See generally Ind. Code ch. 8-1-39 (2016 Repl.). 1 This statute
    provides two distinct, yet related, types of proceedings. First, under
    Section 10, a utility can seek approval from the Commission of a multi-
    year plan “for eligible transmission, distribution, and storage
    improvements.” I.C. § 8-1-39-10(a). See also NIPSCO 
    2018, 100 N.E.3d at 239
    . Second, under Section 9 and based on the multi-year plan, the utility
    can periodically petition the Commission for “adjustment of [its] basic
    rates and charges to provide for timely recovery of eighty percent (80%) of
    approved capital expenditures and TDSIC costs.” I.C. § 8-1-39-9(a). See
    also NIPSCO 
    2018, 100 N.E.3d at 239
    . The utility calculates these rate
    adjustments through a multi-step process, and one of the steps in this
    process involves allocating eligible TDSIC costs among the utility’s
    various rate classes.
    One requirement of Section 9 of the TDSIC Statute speaks specifically to
    the allocation step of the rate adjustment calculation, and this requirement
    lies at the center of this appeal. A Section 9 petition, among other things,
    must “use the customer class revenue allocation factor based on firm load
    approved in the public utility’s most recent retail base rate case order.”
    I.C. § 8-1-39-9(a)(1). The parties agree as to which order from the
    Commission qualifies as Northern Indiana Public Service Company’s
    (“NIPSCO”) 2 most recent retail base rate case order. Further, the parties
    do not dispute the meaning of the term “firm load” in the context of this
    1 The legislature has recently amended the TDSIC Statute. See Pub. L. No. 89-2019, §§ 1–9,
    2019 Ind. Acts ___. And our NIPSCO 2018 decision analyzed some portions of the TDSIC
    Statute that have now been amended. Compare, e.g., NIPSCO 2018, 242–43 (analyzing the
    word “designate” included in the then-applicable version of the TDSIC Statute) with Pub. L.
    No. 89-2019, §§ 1, 4, 2019 Ind. Acts ___ (removing the word “designate” from the TDSIC
    Statute). However, the recent amendments to the TDSIC Statute do not affect the continued
    validity of the analysis in NIPSCO 2018 that we cite in this decision and do not impact the
    issues raised in this appeal.
    2   NIPSCO is a utility that provides gas and electric service to more than 800,000 customers.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019                           Page 4 of 18
    proceeding. 3 However, the NIPSCO Industrial Group (the “Industrial
    Group”) 4 argues that the customer class revenue allocation factors
    included in NIPSCO’s second Section 9 petition were not based on firm
    load, as required by Section 9, but rather on total load.
    II. NIPSCO’s most recent base rate case and its
    Section 10 proceeding for approval of its multi-
    year TDSIC plan
    Because the Section 9 proceeding that spawned this appeal drew from
    the parties’ settlements and the Commission’s orders resolving NIPSCO’s
    most recent base rate case and approving NIPSCO’s multi-year TDSIC
    plan, we begin our discussion of the particular facts and history of this
    appeal with a discussion of the underlying proceedings.
    A. The base rate case
    In October 2015, NIPSCO petitioned the Commission to begin a base
    rate case to increase its base electric service rates, and it submitted
    testimony and exhibits to the Commission. 5 Nine entities intervened and
    participated in the case, including the Industrial Group. The Indiana
    Office of Utility Consumer Counselor (the “OUCC”), a statutory
    representative of “ratepayers, consumers, and the public,” I.C. § 8-1-1.1-
    4.1(a), also participated in the case.
    3Although “firm load” is not defined for purposes of the TDSIC Statute, the parties referred
    to it as utility service provided with a high level of reliability. This contrasts with “non-firm
    load” or “interruptible load,” which the parties treated as utility service that can be
    interrupted based on the needs of other utility customers and is thus less reliable. Total load,
    then, refers to the sum of firm and interruptible loads.
    4The Industrial Group is a group consisting of some of NIPSCO’s largest industrial
    customers.
    5   The case proceeded under Cause Number 44688 before the Commission.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019                           Page 5 of 18
    In February 2016, NIPSCO, the OUCC, and most of the intervenors—
    including the Industrial Group—submitted a settlement agreement (the
    “Base Rate Case Settlement”) to the Commission, along with supporting
    testimony. As relevant here, the settling parties stated, “For purposes of
    establishing any rate schedules allowing for the recovery of 80% of
    NIPSCO’s approved capital TDSIC expenditures and costs pursuant to
    I.C. 8-1-39-9(a), the parties agree that Joint Exhibit D reflects the customer
    class revenue allocation factors that should be applied to firm load.”
    Appellant’s App. Vol. II, p. 223. Joint Exhibit D then provided allocation
    factor percentages for each of NIPSCO’s electric rate classes. 6 
    Id. at 246.
    On July 18, 2016, the Commission approved the Base Rate Case
    Settlement and entered an order generally in line with the settlement (the
    “Base Rate Case Order”). Specific to the issues raised in this appeal, the
    Commission “approve[d] the customer class revenue allocation factors
    shown in Joint Exhibit D” for use in subsequent TDSIC proceedings. 
    Id. at 177.
    In coming to this conclusion, it noted that Joint Exhibit D to the Base
    Rate Case Settlement resolved a “significant issue [regarding] the
    allocation of costs recovered through [r]iders” and was “not opposed by
    any party.” 
    Id. at 154,
    177.
    B. The TDSIC multi-year plan
    In December 2015, while its base rate case was pending, NIPSCO
    petitioned the Commission for approval of a multi-year TDSIC plan
    pursuant to Section 10 of the TDSIC Statute. Five entities—one of which
    was the Industrial Group—intervened, and they, along with the OUCC,
    participated in the proceeding.
    In March 2016, NIPSCO, the OUCC, and four of the five intervenors—
    including the Industrial Group—submitted a settlement agreement (the
    6Joint Exhibit D provided two allocation factor percentages for each rate class to differentiate
    between costs specific to NIPSCO’s transmission system and its distribution system. The
    parties on appeal do not challenge this method of allocating between transmission and
    distribution costs.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019                          Page 6 of 18
    “TDSIC Plan Settlement”) to the Commission, along with supporting
    testimony. The settling parties specified that “[t]he allocation factors for
    NIPSCO’s TDSIC rider shall be those from NIPSCO’s 2016 base rate case
    in Cause No. 44688.” Appellant’s App. Vol. III, p. 142. They further
    “agree[d] that using such factors complies with the TDSIC statute.” 
    Id. The agreement
    on the TDSIC allocation factors was so important to the
    settling parties that they expressly based their assent to the terms of the
    settlement on “the Commission’s approval of the application of the
    allocation factors for TDSIC expenditures reflected in Joint Exhibit D to
    the [Base Rate Case] Settlement.” 
    Id. at 144.
    On July 12, 2016, the Commission approved the TDSIC Plan Settlement
    and entered an order in accordance with the settlement (the “TDSIC Plan
    Order”). The Commission noted that, in “resolv[ing] a number of
    previously contested issues in a manner consistent with the TDSIC
    statute,” the TDSIC Plan Settlement “provides clarity and predictability in
    a manner consistent with the public interest and administrative
    efficiency.” 
    Id. at 133.
    It further concluded that compromises as to the
    implementation of TDSIC allocation factors were “evident” and that these
    compromises were “consistent with the applicable statutory provisions
    and [were] reasonable and in the public interest.” 
    Id. As discussed
    above, the Commission entered its Base Rate Case Order
    shortly after entering its TDSIC Plan Order. With these two orders
    entered, the parties to this appeal—NIPSCO, the Industrial Group, and the
    OUCC—and others had established a thorough, agreed-upon procedure
    under which NIPSCO would seek recovery of its TDSIC costs.
    III. NIPSCO’s Section 9 petitions and this appeal
    NIPSCO’s first Section 9 petition was approved by the Commission in
    January 2017. 7 In this petition, NIPSCO conducted the multi-step
    calculation of its rate adjustments using, among other things, the customer
    7   We refer to this proceeding generally as TDSIC-1.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019          Page 7 of 18
    class revenue allocation factors contained in Joint Exhibit D to the Base
    Rate Case Settlement and approved in the Base Rate Case Order. Neither
    the Industrial Group nor the OUCC objected to this calculation.
    NIPSCO filed its second Section 9 petition—the subject of this appeal—
    in June 2017. 8 In this petition, NIPSCO made some changes to its
    calculation and allocation from TDSIC-1, but, relevant here, it continued
    to use the same allocation factors from the Base Rate Case Settlement as it
    had used in TDSIC-1. Subject to a few suggested alterations to the petition
    not relevant to this appeal, the OUCC recommended that the Commission
    approve NIPSCO’s TDSIC-2 petition.
    The Industrial Group intervened in opposition to NIPSCO’s TDSIC-2
    petition. The Industrial Group argued that the customer class revenue
    allocation factors NIPSCO used in TDSIC-2 were not based on firm load as
    required by Section 9 of the TDSIC Statute but rather were based on total
    load. To correct the alleged deficiencies in TDSIC-2, the Industrial Group
    suggested that NIPSCO could follow the same calculation and allocation
    methodology it used in TDSIC-1 or it could revise the allocation factors.
    The Commission rejected the Industrial Group’s arguments and largely
    approved NIPSCO’s TDSIC-2 petition. In its order, the Commission
    summarized testimony submitted by NIPSCO, the Industrial Group, and
    the OUCC, noting issues on which the parties’ experts disagreed. It
    recited the requirement from Section 9 of the TDSIC Statute that “the
    Petition must use the customer class revenue allocation factor based on
    firm load approved in the public utility’s most recent retail base rate case
    order.” Appellant’s App. Vol. II, p. 15 (citing I.C. § 8-1-39-9(a)(1)). It then
    stated, “Specific to the evidence of this proceeding, the Parties explicitly
    agreed to and the Commission approved the allocation factors established
    in the [Base] Rate Case Settlement and the [TDSIC Plan] Settlement. Those
    agreements leave no question as to what factors would be applied . . . .”
    
    Id. Thus, the
    Commission concluded that “NIPSCO is authorized to
    allocate transmission and distribution revenue requirements by using the
    8   We refer to this proceeding generally as TDSIC-2.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019          Page 8 of 18
    allocation percentages contained on Joint Exhibit D as previously
    approved in Cause No. 44688.” 
    Id. at 19.
    The Industrial Group sought review of the Commission’s TDSIC-2
    order before the Court of Appeals 9 and raised two broad issues. In line
    with its contentions before the Commission, the Industrial Group
    primarily argued that the Commission’s TDSIC-2 order allowed NIPSCO
    to use allocation factors based on total load contrary to the TDSIC
    Statute’s requirement that the allocation factors be based on firm load.
    Additionally, the Industrial Group argued that the TDSIC-2 order lacked
    sufficient findings. In a joint appellees’ brief, NIPSCO and the OUCC
    responded that the Industrial Group was estopped from challenging the
    terms of the underlying settlements, that the Commission’s decision to
    approve the TDSIC-2 petition was owed strong deference, and that the
    TDSIC-2 order contained sufficient findings.
    The Court of Appeals reversed the Commission. NIPSCO Indus. Grp. v.
    N. Ind. Pub. Serv. Co., 
    104 N.E.3d 603
    (Ind. Ct. App. 2018). It found that the
    customer class revenue allocation factors included in Joint Exhibit D to the
    Base Rate Case Settlement “were determined based on total load” despite
    the requirement that they be based on firm load. 
    Id. at 610.
    Thus, it
    “conclude[d] that the Commission exceeded its statutory authority by
    allowing a rate adjustment based on allocation factors computed on total
    load.” 
    Id. at 611.
    We granted the joint petition to transfer filed by NIPSCO and the
    OUCC, thereby vacating the Court of Appeals opinion. See Ind. Appellate
    Rule 58(A).
    9Review of Commission final orders takes place in the Court of Appeals rather than a circuit
    or superior court. I.C. § 8-1-3-1; Hamilton Se. Utils., Inc. v. Ind. Util. Regulatory Comm’n, 
    101 N.E.3d 229
    , 232 (Ind. 2018).
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019                            Page 9 of 18
    Standard of Review
    Indiana Code section 8-1-3-1 supplies the basis for our review of the
    Commission’s TDSIC-2 order. See N. Ind. Pub. Serv. Co. v. U.S. Steel Corp.
    (U.S. Steel), 
    907 N.E.2d 1012
    , 1015 (Ind. 2009) (citing I.C. § 8-1-3-1 (2008)).
    It provides:
    An assignment of errors that the decision, ruling, or order of
    the commission is contrary to law shall be sufficient to present
    both the sufficiency of the facts found to sustain the decision,
    ruling, or order, and the sufficiency of the evidence to sustain
    the finding of facts upon which it was rendered.
    I.C. § 8-1-3-1 (2018). When presented with an appeal under this section,
    we apply three levels of review: “one for factual findings; another for
    mixed questions of law and fact; and a third for questions of law.”
    NIPSCO 
    2018, 100 N.E.3d at 241
    . See also U.S. 
    Steel, 907 N.E.2d at 1015
    –18
    (describing the levels of review). The Industrial Group’s arguments
    addressed below involve only the second level of review.
    Appeals involving claims of insufficient findings to sustain the ultimate
    conclusions contained in the order present questions of ultimate fact—or
    mixed questions of law and fact. See Ind. Gas Co. v. Ind. Fin. Auth., 
    999 N.E.2d 63
    , 66 (Ind. 2013). In these cases, we review the Commission’s
    conclusions for reasonableness, deferring to the Commission “based on
    the amount of expertise exercised by [it].” U.S. 
    Steel, 907 N.E.2d at 1016
    (citation omitted). Thus, we give more deference to orders on subjects
    within the Commission’s expertise and less deference to orders dealing
    with matters outside its expertise. 
    Id. “In either
    case, courts may examine
    the logic of inferences drawn and any rule of law that may drive the
    result.” 
    Id. Indiana Supreme
    Court | Case No. 18S-EX-475 | June 27, 2019           Page 10 of 18
    Discussion and Decision
    The TDSIC Statute “encourages energy utilities to replace their aging
    infrastructure by modernizing electric or gas transmission, distribution,
    and storage” systems. NIPSCO 
    2018, 100 N.E.3d at 238
    . Presumably
    understanding that these modernization projects require significant
    investments of time and money, the legislature drafted the TDSIC Statute
    to allow utilities to first petition the Commission for approval of a multi-
    year TDSIC plan and then petition the Commission for periodic rate
    adjustments based on its progress. See generally I.C. §§ 8-1-39-9, -10 (2016).
    This complex, long-term process allows for some stability and
    predictability on both sides of the utility transaction: utilities can count on
    recouping their investment in upgraded infrastructure, and individuals
    and businesses in Indiana can count on the efficient and reliable provision
    of much-needed gas and electric services.
    The primary issue in this appeal is whether the Commission
    improperly approved of the use of customer class revenue allocation
    factors based on total load rather than firm load as required by the TDSIC
    Statute. See I.C. § 8-1-39-9(a)(1) (requiring that Section 9 petitions “use the
    customer class revenue allocation factor based on firm load approved in
    the public utility’s most recent retail base rate case order”). The Industrial
    Group also presents us with a secondary argument challenging whether
    the Commission’s TDSIC-2 order contained specific findings supporting
    its ultimate conclusion in approving the TDSIC-2 petition. We address
    both issues in turn below.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019          Page 11 of 18
    I.    The Industrial Group’s primary argument against
    the TDSIC-2 order is, in reality, an attack on the
    underlying settlements and orders, and the
    Industrial Group is estopped from bringing this
    challenge now.
    A. The Industrial Group’s argument challenges the
    customer class revenue allocation factors contained in
    the Base Rate Case Settlement rather than any unique
    feature of the TDSIC-2 order.
    The Industrial Group’s principal argument, weaved throughout its
    briefing, is that Section 9 of the TDSIC Statute requires customer class
    revenue allocation factors to be based on firm load, but the allocation
    factors here were based on total load instead. Resp. in Opposition to
    Transfer, pp. 8–9; see also 
    id. at 8,
    10, 12, 17 (referring to the alleged
    statutory violation in every top-level heading of the argument); Br. of
    Appellant NIPSCO Industrial Group, p. 18 (beginning its summary of the
    argument by describing the alleged statutory violation). The Industrial
    Group frames this argument in terms of only the TDSIC-2 order, but it is
    not based on any unique feature of the order. The TDSIC-2 order merely
    pointed NIPSCO to the allocation factors in the Base Rate Case Settlement
    for use in this and future Section 9 petitions. Appellant’s App. Vol. II, p.
    19. This instruction follows the overall TDSIC procedure—agreed to in
    the TDSIC Plan Settlement and approved in the TDSIC Plan Order—that
    Section 9 petitions would use the allocation factors from the Base Rate
    Case Settlement. Appellant’s App. Vol. III, p. 131 (directing in the order
    that “[t]he allocation factors to be used in NIPSCO TDSIC tracker filings
    will be those from Cause No. 44688”); 
    id. at 142
    (agreeing in the settlement
    that “[t]he allocation factors for NIPSCO’s TDSIC rider shall be those from
    NIPSCO’s 2016 base rate case in Cause No. 44688”). Indeed, the Industrial
    Group’s witness testified that NIPSCO relied on the allocation factors
    from Joint Exhibit D to the Base Rate Case Settlement in both TDSIC-1 and
    TDSIC-2. Non-Conf. Ex. Vol. 2, pp. 185–86. Thus, while the Industrial
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019       Page 12 of 18
    Group frames its argument as challenging the Commission’s approval of
    the TDSIC-2 petition, the substance of its argument centers on the
    allocation factors contained in Joint Exhibit D to the Base Rate Case
    Settlement, approved in the Base Rate Case Order, and referenced in the
    TDSIC Plan Settlement and TDSIC Plan Order. As a result, we will
    consider this argument for what it really is: a challenge to the terms of the
    Base Rate Case Settlement and the related order.
    When the Industrial Group’s arguments are viewed in the proper
    context of coming from a challenger that was a party to—and, before the
    Commission, an advocate of—settlements of both a base rate case and a
    petition for approval of a multi-year TDSIC plan, NIPSCO and the
    OUCC’s estoppel argument becomes more compelling. See Br. of
    Appellees NIPSCO and OUCC, pp. 22–23 (raising estoppel as a bar to the
    Industrial Group’s challenge).
    B. The Industrial Group is estopped from challenging the
    terms of the Base Rate Case Settlement.
    In a general sense, estoppel forces a party to follow through on what it
    says or otherwise represents it will do. More specifically, we have said it
    “is a concept by which one’s own acts or conduct prevents the claiming of
    a right to the detriment of another party who was entitled to and did rely
    on the conduct.” Ashby v. Bar Plan Mut. Ins. Co., 
    949 N.E.2d 307
    , 313 (Ind.
    2011) (quoting Brown v. Branch, 
    758 N.E.2d 48
    , 51–52 (Ind. 2001)). See also
    Estoppel, BLACK’S LAW DICTIONARY (10th ed. 2014) (defining estoppel
    as “[a] bar that prevents one from asserting a claim or right that
    contradicts what one has said or done before . . .”). It is based on
    principles of equity and “aid[s] the law in the administration of justice
    where, without its aid, injustice might result.” First Nat’l Bank of
    Logansport v. Logan Mfg. Co., 
    577 N.E.2d 949
    , 954 (Ind. 1991). While
    estoppel comes in many different forms, all its forms “are based on the
    same underlying principle: one who by deed or conduct has induced
    another to act in a particular manner will not be permitted to adopt an
    inconsistent position, attitude, or course of conduct that causes injury to
    such other.” 
    Brown, 758 N.E.2d at 52
    . With these foundational principles
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019        Page 13 of 18
    of estoppel guiding our analysis, we conclude that the Industrial Group is
    estopped from challenging the use of the customer class revenue
    allocation factors from the Base Rate Case Settlement and related order at
    this time.
    In both the base rate case and the TDSIC multi-year plan proceeding,
    the Industrial Group supported the use of the allocation factors from the
    Base Rate Case Settlement and related order—a position NIPSCO relied
    on in later TDSIC proceedings. Not only did the Industrial Group join the
    Base Rate Case Settlement that provides the allocation factors it now
    challenges but it also offered testimony before the Commission in support
    of the settlement. See Non-Conf. Ex. Vol. 4, p. 7 (characterizing, in its
    witness’s testimony, the settlement as a “comprehensive agreement that
    resolve[d] both revenue and the complex allocation and rate mitigation
    issues in this rate case”). Specifically regarding the allocation factors, the
    Industrial Group’s witness testified that they “provide a comprehensive
    method for allocating NIPSCO’s base rates as well as tracked expenses,
    which is reasonable and in the public interest.” 
    Id. at 11.
    Later, the
    Industrial Group doubled down on its support for the allocation factors
    included in the Base Rate Case Settlement when it joined in the TDSIC
    Plan Settlement that was “expressly predicated upon . . . the
    Commission’s approval of the application of the allocation factors for
    TDSIC expenditures reflected in Joint Exhibit D to the [Base Rate Case]
    Settlement . . . .” Appellant’s App. Vol. III, p. 144. Relying on these
    agreements fully supported by the Industrial Group, NIPSCO began filing
    periodic rate adjustment petitions pursuant to Section 9 of the TDSIC
    Statute. When NIPSCO filed its TDSIC-1 petition that used the allocation
    factors from the Base Rate Case Settlement, the Industrial Group did not
    object. Only when NIPSCO filed its TDSIC-2 petition—which used the
    same allocation factors as the TDSIC-1 petition used and as the TDSIC
    Plan Settlement and the Base Rate Case Settlement provided—did the
    Industrial Group object. Thus, up until TDSIC-2, the Industrial Group
    approved using the allocation factors from the Base Rate Case Settlement,
    and NIPSCO relied on that approval in moving forward with its TDSIC
    multi-year plan.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019         Page 14 of 18
    Allowing the Industrial Group to reverse course now and object to the
    use of the allocation factors at this late stage would harm NIPSCO and the
    broader utility regulatory and infrastructure systems involved in this case.
    The TDSIC Statute contemplates many related proceedings over the
    course of several years with an underlying base rate case and a TDSIC
    multi-year plan providing the foundation for periodic rate adjustment
    petitions. The Industrial Group’s argument challenging the allocation
    factors provided in the underlying Base Rate Case Settlement seeks to
    undermine the foundation on which the later TDSIC proceedings have
    been built. With the Base Rate Case Settlement in question, NIPSCO—not
    to mention the other parties to the Base Rate Case Settlement and the
    TDSIC Plan Settlement—would then need to spend considerable resources
    adjusting the plans laid out in the settlements, striking entirely new
    settlement agreements, or proceeding with contested cases before the
    Commission. And, in light of the equitable underpinnings of the estoppel
    doctrine, we cannot lose sight of the fact that the injury would spread
    beyond NIPSCO. The OUCC, a statutory representative of “ratepayers,
    consumers, and the public,” I.C. § 8-1-1.1-4.1(a) (2016 Repl.), has joined
    NIPSCO in opposing the Industrial Group’s appeal. Allowing the
    Industrial Group’s delayed attacks against the Base Rate Case Settlement
    would risk disrupting the public’s interest in stable and modern electric
    and gas transmission, distribution, and storage infrastructure systems by
    hindering long-approved efforts at modernization. Further, permitting
    these tardy attacks would reduce parties’ and the public’s confidence in
    the durability of long-term regulatory settlements and orders. In light of
    the long-term, integrated procedures contemplated by the TDSIC Statute,
    allowing the Industrial Group to belatedly challenge the underlying
    settlement in NIPSCO’s base rate case would harm NIPSCO and the
    broader systems involved in utility regulation and supply.
    Because the Industrial Group’s support for the Base Rate Case
    Settlement induced NIPSCO to rely on that settlement and the related
    order in subsequent TDSIC proceedings and because allowing the
    Industrial Group to change its position and raise this challenge would
    injure NIPSCO, the Industrial Group is estopped from challenging the use
    of the customer class revenue allocation factors now. This conclusion is in
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019       Page 15 of 18
    line with the “general proposition” laid out by the Supreme Court of the
    United States long ago that, if a party takes “a certain position in a legal
    proceeding, and succeeds in maintaining that position, he may not
    thereafter, simply because his interests have changed, assume a contrary
    position, especially if it be to the prejudice of the party who has
    acquiesced in the position formerly taken by him.” Davis v. Wakelee, 
    156 U.S. 680
    , 689 (1895). It is also in line with prior decisions of this Court in
    which we rejected parties’ attempts to change course from earlier
    positions taken. See, e.g., Speckman v. City of Indianapolis, 
    540 N.E.2d 1189
    ,
    1191 (Ind. 1989) (finding the city was estopped from arguing that a
    contract was not binding on it when the contract stipulated that the city’s
    counsel had reviewed the contract and found it to be proper); United States
    v. Fletcher Sav. & Tr. Co., 
    197 Ind. 527
    , 537–38, 
    151 N.E. 420
    , 423 (1926)
    (rejecting an argument by the United States that a prior payment did not
    strictly comply with a contract when the United States had previously
    concluded that the contract was not a valid contract). The Industrial
    Group’s delay in challenging the allocation factors contained in the Base
    Rate Case Settlement and related order understandably caused NIPSCO to
    rely on the Industrial Group’s support for those allocation factors in later
    TDSIC proceedings, and allowing this delayed challenge now would
    harm NIPSCO and the larger systems used to regulate utilities and to
    provide utility service to the public. As a result, the Industrial Group is
    estopped from now challenging NIPSCO’s use of the allocation factors.
    II. The Commission’s TDSIC-2 order contains
    specific findings supporting its conclusion.
    The Industrial Group also argues that the TDSIC-2 order lacks specific
    findings supporting the Commission’s ultimate conclusions. Br. of
    Appellant, p. 36 (citing L.S. Ayers & Co. v. Indianapolis Power & Light Co.,
    
    169 Ind. App. 652
    , 662, 
    351 N.E.2d 814
    , 822 (1976)). In issuing its orders,
    the Commission must include “specific findings on all the factual
    determinations material to its ultimate conclusions.” U.S. 
    Steel, 907 N.E.2d at 1016
    . An appeal based on an alleged lack of specific findings presents a
    mixed question of law and fact. Ind. Fin. 
    Auth., 999 N.E.2d at 66
    . In these
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019        Page 16 of 18
    situations, we review the Commission’s conclusions for reasonableness,
    deferring to the Commission “based on the amount of expertise exercised
    by [it].” U.S. 
    Steel, 907 N.E.2d at 1016
    (citation omitted).
    In line with our analysis above, the Commission recognized that the
    Industrial Group’s challenge centered on the Base Rate Case Settlement
    and the TDSIC Plan Settlement, along with their related orders. See
    Appellant’s App. Vol. II, pp. 13, 15 (discussing the settlements and
    orders). “Approving such [settlements] and resolving disputes revolving
    around them [are] intrinsic to the Commission’s regulation of utility
    rates.” U.S. 
    Steel, 907 N.E.2d at 1018
    . And, in resolving disputes over
    settlement agreements it has previously approved, the Commission
    deploys its expertise of both the terms of the settlement and the regulation
    of utility rates. 
    Id. at 1017–18.
    Thus, in reviewing the Industrial Group’s
    challenge to the sufficiency of the Commission’s findings involving a
    previously-approved settlement concerning utility rate regulation, we
    give the Commission greater deference.
    Despite the Industrial Group’s arguments to the contrary, the
    Commission supported its conclusion to approve the TDSIC-2 petition
    with specific findings. The Commission began its discussion of the
    allocation factors by summarizing the conflicting testimony presented to it
    in TDSIC-2 by NIPSCO and the Industrial Group. Appellant’s App. Vol.
    II, p. 13. It noted that the allocation factors in NIPSCO’s TDSIC-2 petition
    came from the Base Rate Case Settlement and were approved in the Base
    Rate Case Order. 
    Id. It also
    noted that the parties to the TDSIC Plan
    Settlement provided that the allocation factors from the Base Rate Case
    Settlement should be used in TDSIC proceedings based on the multi-year
    TDSIC plan, and they “agree[d] that using such factors complies with the
    TDSIC Statute.” 
    Id. (citation omitted).
    Based on these findings, the
    Commission concluded, “Specific to the evidence of this proceeding, the
    [p]arties explicitly agreed to and the Commission approved the allocation
    factors established in the [Base] Rate Case Settlement and the [TDSIC
    Plan] Settlement. Those agreements leave no question as to what factors
    would be applied . . . .” 
    Id. at 15.
    In light of the findings in this case and
    the Commission’s expertise in this area, the Commission’s conclusion was
    reasonable and properly supported by specific findings.
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019         Page 17 of 18
    Conclusion
    For these reasons, we affirm the order of the Commission.
    Rush, C.J., and Massa, J., concur.
    Slaughter, J., dissents with separate opinion in which David, J., joins.
    ATTORNEYS FOR APPELLANT
    Todd A. Richardson
    Bette J. Dodd
    Joseph P. Rompala
    Lewis & Kappes, P.C.
    Indianapolis, Indiana
    ATTORNEYS FOR APPELLEE NORTHERN INDIANA PUBLIC
    SERVICE COMPANY
    Brian J. Paul
    Daniel E. Pulliam
    Faegre Baker Daniels LLP
    Indianapolis, Indiana
    Claudia J. Earls
    M. Bryan Little
    NiSource Corporate Services – Legal
    Indianapolis, Indiana
    ATTORNEYS FOR APPELLEE OFFICE OF THE UTILITY
    CONSUMER COUNSELOR
    Jeffrey M. Reed
    William I. Fine
    Randall C. Helmen
    Tiffany T. Murray
    Office of the Utility Consumer Counselor
    Indianapolis, Indiana
    Indiana Supreme Court | Case No. 18S-EX-475 | June 27, 2019    Page 18 of 18
    Slaughter, J., dissenting.
    I respectfully dissent, believing that this case concerns an issue of law
    the court of appeals decided correctly, and not a matter of regulatory
    discretion warranting agency deference. On the merits, I agree with the
    court of appeals that the utility regulatory commission exceeded its
    statutory authority by approving a rate adjustment based on allocation
    factors computed on total load rather than firm load. I would either deny
    transfer or summarily affirm the court of appeals’ opinion.
    David, J., joins.