Primacy of Idaho’s “Just and Reasonable” Mandate Over Multi‑State Allocation Protocols: Commentary on PacifiCorp v. Idaho Public Utilities Commission

I. Introduction

The Idaho Supreme Court’s decision in PacifiCorp v. Idaho Public Utilities Commission addresses a growing and legally complex problem: how a non‑climate‑policy state treats the costs that a neighboring state’s climate law imposes on a multi‑state, investor‑owned utility.

PacifiCorp, doing business in Idaho as Rocky Mountain Power, owns a natural gas generating facility in Chehalis, Washington. Washington’s Climate Commitment Act (“CCA”), Wash. Rev. Code §§ 70A.65.005–.901, establishes a “cap and invest” program that requires large greenhouse gas emitters to obtain emission “allowances.” Operating the Chehalis plant therefore entails compliance costs under Washington law, even for electricity exported to Idaho.

PacifiCorp sought to recover approximately $2.3 million of these CCA allowance costs from Idaho customers through Idaho’s Energy Cost Adjustment Mechanism (“ECAM”)—a device intended to true‑up annual power supply costs. The Idaho Public Utilities Commission (“Commission”) allowed more than $60 million in other deferred power costs, but disallowed recovery of the CCA allowance costs from Idaho ratepayers.

The Commission’s decision rested on two independent rationales:

Its interpretation of the 2020 PacifiCorp Inter‑Jurisdictional Allocation Protocol (“2020 Protocol” or “Protocol”), which treats “state‑specific” energy and climate policies as costs borne by the enacting jurisdiction (here, Washington).
Its statutory duty under Idaho Code § 61‑502 to ensure “just, reasonable or sufficient” rates for Idaho customers, a duty which it concluded would be violated by shifting Washington’s climate‑policy costs onto Idahoans while Washington customers are explicitly shielded by “no‑cost” allowances.

PacifiCorp appealed, arguing that CCA allowance costs are ordinary “generation‑related dispatch costs” that must be shared system‑wide under the Protocol, and that the Commission improperly focused only on Idaho customers, not on whether disallowance was “just and reasonable” from PacifiCorp’s perspective as well.

The Idaho Supreme Court affirmed the Commission, but on a narrow and important ground: it held that the Commission’s independent statutory authority under § 61‑502 to set just and reasonable rates was alone sufficient to sustain the disallowance. Because the Protocol expressly does not “abrogate” any commission’s duty to determine fair, just, and reasonable rates, the Court declined to reach the Protocol‑interpretation question at all.

In doing so, the Court reinforces two central principles:

Idaho’s statutory “just and reasonable” mandate under § 61‑502 is primary and cannot be contractually displaced by a multi‑state cost allocation agreement.
Within a broad “zone of reasonableness,” the Commission has discretion to decide that out‑of‑state climate compliance costs—especially where the originating state legally shields its own retail customers—need not be imposed on Idaho ratepayers.

This commentary analyzes the Opinion’s structure, its use of precedent, its clarification of the standard of review, and the implications for multi‑state utilities confronting climate regulation in only some of their service territories.

II. Summary of the Opinion

A. Regulatory Context and the ECAM Application

PacifiCorp operates as a multi‑state utility serving six western states, including Idaho and Washington. To allocate the costs and benefits of its shared, interstate generation fleet (such as the Chehalis plant), PacifiCorp and stakeholders from all six states negotiated the 2020 Protocol, which the Idaho Commission approved in 2020 as a tool for determining “just and reasonable” Idaho rates.

In April 2024, PacifiCorp filed an ECAM application with the Commission. The ECAM allows annual true‑ups between:

Actual net power costs incurred, and
Net power costs embedded in base rates previously approved by the Commission.

PacifiCorp reported approximately $42 million in CCA allowance purchases related to operation of the Chehalis plant, roughly $2.3 million of which it sought to allocate to Idaho as Idaho’s jurisdictional share. Commission staff and large industrial customers (P4 Production and PacifiCorp Idaho Industrial Customers) opposed allowing Idaho customers to bear these Washington‑imposed compliance costs.

B. Commission’s Orders

In its initial order, the Commission:

Approved recovery of more than $60 million in other ECAM deferred costs; but
Disallowed the $2,306,040 in CCA allowance costs allocated to Idaho customers.

Key findings in the initial order included:

The CCA caps greenhouse gas emissions in Washington and enforces compliance by auctioning a limited number of allowances, with penalties for non‑compliance.
Washington separately provides “no‑cost allowances” to electric utilities, but only on the condition that they be allocated to Washington retail customers, as a way to shield them from incremental transition costs and to complement Washington’s Clean Energy Transformation Act (CETA).
The Chehalis plant emits CO₂ in Washington and exports some of its electricity to Idaho customers; PacifiCorp’s requested $2.3 million represented Idaho’s share of the paid allowances needed to cover emissions from Chehalis exports out of Washington.

The Commission concluded that under the 2020 Protocol, Washington’s CCA is a “state‑specific energy and climate policy” whose costs should not be allocated system‑wide, and thus disallowed recovery.

PacifiCorp petitioned for reconsideration. The Commission allowed additional briefing and testimony but ultimately denied reconsideration. In its order on reconsideration, the Commission reiterated its Protocol interpretation and—critically—added an independent statutory rationale: even if the Protocol permitted recovery, § 61‑502 would prohibit it as unjust, unreasonable, and insufficient.

Focusing on the CCA’s asymmetric distribution of no‑cost allowances, the Commission determined that if Idaho customers alone bore CCA allowance costs (while Washington customers did not), it would “result in the creation of discriminatory customer classes.” For that reason, separate and apart from any Protocol analysis, recovery of the CCA compliance costs from Idaho ratepayers would violate the Commission’s rate‑making mandate.

C. Idaho Supreme Court’s Holding

On appeal, PacifiCorp challenged:

The Commission’s interpretation and application of the 2020 Protocol, and
The Commission’s reliance on § 61‑502 to disallow recovery of CCA costs.

The Idaho Supreme Court:

Articulated a highly deferential standard of review under Idaho Code § 61‑629: the Court may only examine whether the Commission “regularly pursued its authority,” including whether its order violates constitutional rights or is unsupported by the evidence.
Emphasized that the 2020 Protocol, by its own terms, does not abrogate any commission’s duty to determine fair, just, and reasonable rates.
Held that the Commission’s reliance on § 61‑502 furnishes an adequate and independent ground to sustain the disallowance of CCA costs.
Declined to address PacifiCorp’s arguments on the Protocol’s interpretation, because the statutory ground alone supports the Commission’s order.

The Court concluded that:

The Commission acted within its statutory authority under § 61‑501 and § 61‑502 to set rates within a “broad zone of reasonableness.”
The Commission reasonably determined that forcing Idaho ratepayers to fund Washington’s climate‑policy costs—while Washington ratepayers enjoy protective no‑cost allowances—would be unjust and discriminatory.
PacifiCorp’s challenge amounts to a policy disagreement with the Commission’s allocation judgment, not a showing of legal error, constitutional violation, or evidentiary failure.

Accordingly, the Court affirmed the Commission’s orders (Order Nos. 36207 and 36367) approving PacifiCorp’s ECAM in a reduced amount, without the challenged CCA allowance costs.

III. Analysis

A. Precedents and Authorities Cited

1. Constitutional and Statutory Framework for Review

Idaho Constitution art. V, § 9 Grants the Idaho Supreme Court jurisdiction to review orders of the Public Utilities Commission, but expressly authorizes the Legislature to define:
- Conditions of appeal,
- Scope of appeal, and
- Procedure on appeal.
Idaho Code § 61‑629 Implements this constitutional structure by sharply limiting the scope of appellate review:
“Review on appeal shall not be extended further than to determine whether the commission has regularly pursued its authority, including a determination of whether the order appealed from violates any right of the appellant under the constitution of the United States or of the state of Idaho.”

This provision is central. It frames the Court’s inquiry not as a de novo ratemaking exercise, but as a legal and evidentiary check on the Commission’s use of its statutory powers.

2. Commission’s Substantive Authority

Idaho Code § 61‑501 Vests the Commission with supervisory authority over “every public utility in the state,” grounding its power in the police power of the state.
Idaho Code § 61‑502 Directs the Commission to:
“determine the just, reasonable or sufficient rates” of public utilities.
This is the core ratemaking mandate at issue. The Court describes it as a grant of “specific police power” to set rates of return within a “broad zone of reasonableness,” relying on earlier case law.

3. Standard of Review: “Regular Pursuit” and Deference

The Court relies on earlier decisions to clarify what “regularly pursued its authority” means in practice.

In re Mountain States Tel. & Tel. Co., 76 Idaho 474, 284 P.2d 681 (1955) The Court’s task is limited to ensuring that the Commission acted within its statutory powers on questions of law.
Rosebud Enters., Inc. v. Idaho Pub. Utils. Comm’n, 128 Idaho 624, 917 P.2d 781 (1996) For factual issues, the Court will sustain the Commission’s determination unless:
- “the clear weight of the evidence is against its conclusion,” or
- the evidence is “strong and persuasive” that the Commission abused its discretion.
In re Ryder, 141 Idaho 918, 120 P.3d 736 (2005) Places the burden on the party challenging the Commission to show that its findings are unsupported by the evidence.

Taken together, these precedents cement a highly deferential review standard. The Court will not reweigh the policy merits of a Commission decision; it will only test whether the Commission’s conclusion is rationally supported by evidence and within statutory bounds.

4. Prior Cases Where the Court Did Intervene

PacifiCorp invoked three older cases in which utilities successfully challenged Commission orders:

Idaho Power Co. v. Idaho Pub. Utils. Comm’n, 99 Idaho 374, 582 P.2d 720 (1978)
Utah Power & Light Co. v. Idaho Pub. Utils. Comm’n (Utah Power & Light I), 102 Idaho 282, 629 P.2d 678 (1981)
Utah Power & Light Co. v. Idaho Pub. Utils. Comm’n (Utah Power & Light II), 105 Idaho 822, 673 P.2d 422 (1983)

The Court explains why none of these decisions control the present case.

a. Idaho Power Co. (1978)

In Idaho Power, the Commission:

Found that the utility was entitled to a particular rate of return, but
Miscomputed that return by double‑deducting $1.6 million in “sales for resale,” resulting in an actual rate of return (8.09%) lower than the Commission’s own determination of what was “fair, just and reasonable.”

This inconsistency rendered the order “virtually nonsensical”: the Commission’s methodology contradicted its stated conclusions. The Court therefore invalidated the order.

In PacifiCorp, by contrast:

The Commission never found PacifiCorp entitled to recover CCA costs; it explicitly found the opposite—that such recovery would be unjust and unreasonable to Idaho customers.
There was no mathematical or logical contradiction between what the Commission said and what it did.

Thus, Idaho Power stands for the narrow proposition that the Court may intervene when a Commission order is internally inconsistent to the point of defeating its own stated ratemaking judgment. No such inconsistency exists here.

b. Utah Power & Light I and II (1981, 1983)

In both Utah Power & Light cases, the Court was confronted with extreme Commission disallowances:

The Commission essentially refused to consider the revenues and expenses associated with an entire powerplant and associated coal mine, and
Offered little to no discernible reasoning for excluding those assets from the utility’s base rate.

The problem, as the Court describes it here, was the wholesale exclusion of major elements of the utility’s operations without explanation.

The current Commission decision differs in several critical respects:

The disallowance here is a single, discrete expense item (CCA allowance costs), not an entire plant or class of assets.
The Commission extensively explained its reasoning based on the CCA’s no‑cost allowance scheme and its impact on Idaho versus Washington customers.
The Commission in fact approved recovery of over 95% of PacifiCorp’s requested ECAM deferrals (more than $60 million).

The Court implies that Utah Power & Light I and II represent the outer boundary of judicial intrusion into ratemaking, with separate opinions in those cases warning against the Court “usurping” the Commission’s role. The present case, involving a modest disallowance grounded in thorough reasoning, sits far from that boundary.

5. Federal Litigation Reference: PacifiCorp v. Watson/Sixkiller

The Opinion briefly notes that the Commission’s understanding of the CCA was “informed by” arguments PacifiCorp raised in federal dormant Commerce Clause litigation:

PacifiCorp v. Watson, No. 3:23‑cv‑06155‑TMC, 2024 WL 3415937 (W.D. Wash. July 15, 2024), appeal docketed sub nom. PacifiCorp v. Sixkiller, No. 90‑567 (9th Cir. argued June 2, 2025).
In that case, PacifiCorp challenged the CCA’s exclusive allocation of no‑cost allowances to Washington residents as violating the dormant Commerce Clause; the district court rejected that claim.

The Idaho Supreme Court does not opine on the merits of that federal case; it cites it only to show that:

The Commission was well‑acquainted with the legal and economic structure of the CCA, and
Had a solid factual basis for understanding its asymmetric treatment of Washington versus out‑of‑state customers.

B. The Court’s Legal Reasoning

1. Central Question: Did the Commission “Regularly Pursue Its Authority” Under § 61‑502?

The Court’s analysis is intentionally narrow. It does not seek to resolve:

Whether the 2020 Protocol, properly construed, classifies CCA allowance costs as “generation‑related dispatch costs” or “state‑specific” policy costs.
Whether, as a matter of economic efficiency, Idaho customers “should” bear part of the CCA costs because they benefit from Chehalis’s output.

Instead, it asks a simpler legal question: Did the Commission act within its statutorily granted discretion when it concluded, under § 61‑502, that recovery of CCA allowance costs from Idaho customers would not result in just and reasonable rates?

The Court answers yes, based on three pillars:

The breadth of the Commission’s ratemaking authority under § 61‑502 and prior case law.
The sufficiency of the Commission’s factual and legal analysis of the CCA’s cost allocation effects.
The absence of any constitutional violation, evidentiary defect, or internal inconsistency comparable to those present in Idaho Power or the Utah Power & Light cases.

2. The Commission’s “Broad Zone of Reasonableness”

The Opinion relies on Utah Power & Light Co. v. Idaho PUC (Utah Power & Light I) for the notion that ratemaking occurs within a “broad zone of reasonableness.” That phrase is important; it underscores that there may be many acceptable answers, not a single “correct” rate or allocation.

Given this breadth, an appellate court should not overturn a Commission decision simply because a different allocation might also be reasonable or more favorable to the utility. Overturning is warranted only when:

The Commission steps outside the zone (e.g., by misapplying law, violating constitutional protections, or making unsupported factual findings), or
The order is internally defective (e.g., saying one thing but doing another, as in Idaho Power).

Here, the Commission’s choice to prioritize Idaho customers’ protection from out‑of‑state climate‑policy costs, given Washington’s self‑protective framework, comfortably falls within the “zone of reasonableness.”

3. Reasoning on § 61‑502: Discriminatory Customer Classes

Section 61‑502 authorizes the Commission to ensure that rates are:

Just,
Reasonable, and
Sufficient.

The Commission’s key finding was that authorizing CCA cost recovery from Idaho ratepayers would create “discriminatory customer classes.” In other words:

Class 1: PacifiCorp’s Washington customers, who do not bear the incremental CCA cost due to no‑cost allowances tied to Washington retail load.
Class 2: PacifiCorp’s Idaho customers, who would have to pay for the CCA allowances associated with Chehalis emissions attributable to exports out of Washington.

The Commission concluded that this asymmetrical burden—Idaho customers financing Washington’s decarbonization policy while Washington customers are statutorily shielded—would be neither just nor reasonable for Idahoans.

The Idaho Supreme Court accepts this reasoning as an archetypal exercise of regulatory judgment. Determining who should bear which costs, especially when those costs arise from another state’s legislative choices, is precisely what § 61‑502 empowers the Commission to decide.

4. Independent Statutory Ground; Protocol Interpretation Unnecessary

Crucially, the Court emphasizes that the 2020 Protocol:

Is a helpful tool for allocating multi‑state costs, but
Explicitly does not “abrogate any Commission’s right or obligation to . . . determine fair, just, and reasonable rates.”

This contractual or quasi‑contractual language in the Protocol means:

The Commission cannot contract away its statutory duty under § 61‑502; and
Even if the Protocol could be read to favor PacifiCorp’s position, it cannot compel the Commission to set rates it deems unjust or unreasonable for Idaho customers.

Because § 61‑502 provides an independent and adequate basis to uphold the Commission’s disallowance, the Court applies a familiar judicial principle: when one ground suffices to affirm, a court need not address alternate grounds. That is why the Court explicitly declines to review the Commission’s interpretation or application of the Protocol.

The practical result is that:

The legal status of CCA allowance costs under the 2020 Protocol remains formally unresolved by this decision.
But, going forward, utilities and stakeholders must recognize that even a Protocol‑based entitlement to recovery cannot override the Commission’s § 61‑502 assessment.

5. Treatment of PacifiCorp’s Efficiency Argument

PacifiCorp argued that the Chehalis plant is the “most cost‑effective source of energy” for Idaho customers and that, as a matter of fairness and economic logic, Idaho customers should share in Chehalis‑related costs, including CCA allowance costs.

The Court implicitly acknowledges that this is a plausible policy argument—but stresses that policy choices of this kind belong to the Commission:

The Commission weighed the benefit of Chehalis power against the CCA’s discriminatory cost structure and chose to protect Idaho customers.
That decision is not arbitrary; it is grounded in a reasoned understanding of Washington law and Idaho’s statutory mandate.

The Court’s refusal to second‑guess this allocation choice underscores again that the appeal amounts to a disagreement over regulatory policy, not a demonstration of legal or constitutional error.

C. Impact and Broader Implications

1. Reinforcing the Primacy of State “Just and Reasonable” Mandates

The most important doctrinal takeaway is that state “just and reasonable” standards are paramount and cannot be displaced by interstate agreements.

For multi‑state utilities, this means:

Inter‑jurisdictional allocation protocols, while binding as frameworks among stakeholders, are always subordinate to each state’s own ratemaking statutes and public interest obligations.
Utilities cannot rely solely on a protocol to guarantee cost recovery if a commission determines that recovery would be unjust or unreasonable for in‑state customers.

This principle effectively restrains any attempt to “federalize” or fully harmonize allocation decisions across multiple states by contract. Each state commission retains veto‑like discretion to adjust or disallow cost components based on its own law and policy judgments.

2. Climate Policy Spillovers and Interstate Cost Allocation

This case illustrates a growing tension in U.S. energy law: how states without binding greenhouse gas policies react when other states impose climate‑related costs on shared infrastructure.

Washington’s approach: Uses the CCA to cap emissions and raise compliance costs, but also provides no‑cost allowances to its own retail customers to avoid rate shock and maintain political acceptability.
Idaho’s position in this case: Declines to have its ratepayers shoulder those same CCA costs, especially where Washington has explicitly shielded its own residents from them.

The Opinion suggests that Idaho will not act as a financial backstop for another state’s climate policy if doing so would create cross‑border inequities in who ultimately pays. That stance may:

Encourage utilities to internalize the risk that climate‑policy costs might not be fully recoverable in non‑policy states.
Prompt utility planning departments to consider the regulatory “recoverability” of climate compliance costs when making siting or dispatch decisions.

3. Implications for Future Multi‑State Protocols

Although the Court does not interpret the 2020 Protocol, its decision will influence how future protocols are drafted and negotiated:

Protocols will likely include even clearer language acknowledging that state commissions retain ultimate authority under their statutes.
Parties may attempt to build in more explicit climate‑policy allocation rules, but must do so in a way that leaves room for each commission’s just‑and‑reasonable analysis.
Utilities may push for symmetrical treatment of decarbonization costs and benefits, but this decision warns that such symmetry is not guaranteed in each state’s ratemaking outcomes.

4. Litigation Strategy and the Role of Federal Law

The Opinion’s brief mention of PacifiCorp’s dormant Commerce Clause challenge to the CCA hints at another route utilities may pursue: federal constitutional challenges to state climate laws that allocate costs asymmetrically to out‑of‑state customers.

However, at least at the state‑commission level, this decision affirms:

A commission may take another state’s self‑protective design (here, no‑cost allowances to Washington retail customers) into account when deciding what is just and reasonable for its own ratepayers.
Such consideration does not itself constitute a constitutional violation; rather, it is an exercise of the commission’s duty to protect in‑state customers.

Unless and until federal courts hold that laws like the CCA violate the dormant Commerce Clause or other federal constraints, state commissions remain free to refuse to pass such costs onto their own ratepayers.

5. Utility Planning and Risk Management

Practically, the decision signals to utilities:

Compliance costs arising from a particular state’s climate policy may be at risk of disallowance in other states if those states’ commissions see the allocation as inequitable or discriminatory.
Capital and operational planning must account for the possibility that climate‑policy costs are not uniformly recoverable across the utility’s footprint.

In the longer run, this may:

Influence where utilities choose to build or retire fossil‑fueled assets.
Shift corporate advocacy towards seeking more geographically neutral climate policies—or federal frameworks—that minimize such asymmetries.

IV. Complex Concepts Simplified

For readers less familiar with utility ratemaking and climate policy, the following explanations may help clarify the Opinion’s key concepts.

1. Energy Cost Adjustment Mechanism (ECAM)

An ECAM is a rate adjustment tool that allows a utility’s rates to be periodically “trued up” to reflect actual power supply costs, which can fluctuate due to:

Fuel prices,
Market purchases,
Hydrological conditions, and
Other operational factors.

Base rates are set assuming certain “base net power costs.” If actual costs are higher, the utility may seek to recover the difference via an ECAM surcharge. If lower, rates may be reduced. The ECAM keeps utilities financially whole while ideally protecting customers from sudden price spikes.

2. Inter‑Jurisdictional Allocation Protocol

For a multi‑state utility like PacifiCorp, many generating assets and transmission lines serve customers in several states simultaneously. An inter‑jurisdictional allocation protocol is a negotiated framework that:

Allocates costs (plant, fuel, compliance, etc.) among states using agreed methods, and
Allocates benefits (like low‑cost power) in a coordinated way.

The 2020 Protocol at issue here generally:

Allocates “generation‑related dispatch costs” and taxes on a systemwide basis.
Allocates “state‑specific” energy and climate policy costs to the state that adopts the policy.

However, as the Court emphasizes, such protocols do not—and legally cannot—override each state commission’s duty to set just and reasonable rates under state law.

3. Washington’s Climate Commitment Act (“Cap and Invest”)

Washington’s CCA establishes a “cap and invest” system:

Cap: The state sets an overall limit (cap) on greenhouse gas emissions.
Allowances: The state issues a limited number of emission allowances, each permitting a specific amount of emissions.
Auctions: Covered entities (like PacifiCorp’s Chehalis plant) must obtain enough allowances, generally by purchasing them at auction, to cover their emissions.
Penalties: Failure to procure or retire sufficient allowances can trigger monetary penalties and “penalty allowances.”

Washington also provides a subset of “no‑cost” allowances to utilities. The key feature in this case is that those no‑cost allowances:

Are conditioned on being allocated only to Washington retail customers, and
Are intended to shield Washington customers from incremental CCA costs as the state transitions to cleaner energy sources (in part under CETA).

4. “Just, Reasonable, or Sufficient” Rates

These are flexible but foundational standards in public utility law. In broad terms:

Just rates fairly balance the interests of the utility and its customers.
Reasonable rates are not excessive, unjustifiably discriminatory, or confiscatory (i.e., they allow a utility to earn a fair return without unduly burdening consumers).
Sufficient rates allow the utility to cover its costs and attract capital to maintain reliable service.

The Commission’s job under § 61‑502 is to determine, in light of all circumstances, whether a proposed rate (or cost component) satisfies these standards for Idaho customers and for the utility.

5. “Regularly Pursued Its Authority”

Under Idaho Code § 61‑629, the Supreme Court does not redo the Commission’s ratemaking work. Instead, it asks whether:

The Commission stayed within the powers granted by statute (like § 61‑502).
The Commission respected constitutional rights.
The Commission’s findings are supported by evidence, not arbitrary or capricious.

If the answer is yes, the Commission is said to have “regularly pursued its authority,” and the Court must affirm—even if it might have reached a different policy outcome were it acting as regulator.

6. Discriminatory Customer Classes

Utility law is sensitive to discrimination among classes of customers. “Discriminatory customer classes” generally refers to situations where:

One group of customers pays more (or receives worse service) without a rational, justifiable basis, solely for the benefit of another group; or
Costs are shifted in ways that lack a coherent nexus to the benefits each group receives.

The Commission found that allowing recovery of CCA costs from Idaho customers, while Washington law shields Washington customers, would create just such an unjustified disparity between two groups of PacifiCorp customers who are similarly situated except for state of residence.

V. Conclusion

PacifiCorp v. Idaho Public Utilities Commission establishes a clear and consequential precedent in Idaho utility law:

The Idaho Public Utilities Commission’s statutory duty under Idaho Code § 61‑502 to set “just, reasonable or sufficient” rates is paramount and cannot be overridden by multi‑state allocation agreements like the 2020 Protocol.
Within a broad zone of reasonableness, the Commission may refuse to pass through out‑of‑state climate compliance costs to Idaho customers when doing so would, in its judgment, create discriminatory customer classes—particularly where the originating state shields its own customers from those same costs.
Appellate review of Commission ratemaking orders is highly deferential: the Idaho Supreme Court will not disturb an order absent constitutional violations, clear evidentiary failure, or internal contradictions akin to those in Idaho Power or the Utah Power & Light cases.

In practical terms, the decision:

Reaffirms the Commission’s discretion to protect Idaho ratepayers from bearing the financial burden of another state’s climate policies.
Signals to multi‑state utilities that climate‑policy compliance costs incurred in one jurisdiction may not be uniformly recoverable in all jurisdictions, especially where the policy design is asymmetric.
Preserves the role of inter‑jurisdictional protocols as important, but ultimately subordinate, tools in the ratemaking process.

As climate regulation continues to evolve unevenly across states, decisions like this one will shape how utilities allocate the rising costs of decarbonization and how state commissions reconcile regional coordination with their core obligation to protect in‑state consumers. PacifiCorp thus stands as a significant marker of Idaho’s commitment to maintaining the primacy of its “just and reasonable” mandate in the face of complex, multi‑state energy and climate dynamics.