New Mexico Adopts a “High Level of Deference” to an Agency’s Interpretation of Its Own Prior Orders

I. Introduction

City of Las Cruces v. N.M. Pub. Regul. Comm'n (N.M. May 11, 2026) arises from Winter Storm Uri’s February 2021 disruption of fuel markets, which drove extraordinary natural gas and electricity prices across the region. Intervenor-Appellee El Paso Electric Company (EPE) relied in part on energy and capacity from Palo Verde Nuclear Generating Station Unit 3 (PV3) to maintain uninterrupted service to New Mexico customers.

The dispute did not challenge EPE’s ability to amortize storm-related extraordinary costs over twelve months. Instead, Appellant City of Las Cruces (City) targeted EPE’s use of a Commission-approved proxy price methodology—derived from natural gas index prices—to price PV3 energy for purposes of EPE’s Fuel and Purchased Power Cost Adjustment Clause (FPPCAC) variance proceeding before the New Mexico Public Regulation Commission (NMPRC or Commission).

The appeal presented (1) a question of first impression about judicial review: what deference (if any) courts owe to the Commission’s interpretation of its own prior orders; and (2) whether the Commission’s application of the PV3 proxy price in this proceeding was lawful and supported by the record.

II. Summary of the Opinion

The Supreme Court of New Mexico affirmed the Commission’s final orders in full. The Court’s central doctrinal move was to adopt a “high level of deference” when reviewing an agency’s interpretation of its own orders. Applying that standard, the Court upheld the Commission’s reading of a chain of prior NMPRC orders (including the 2009 “Credit Suisse Agreement” order and later orders continuing the proxy price), and rejected the City’s arguments that the proxy price authority had lapsed or was misapplied during Winter Storm Uri.

III. Analysis

A. New Rule / Holding: Deference to an Agency’s Interpretation of Its Own Orders

The Court recognized that New Mexico had not previously articulated a standard for reviewing the Commission’s interpretation of its own prior orders. It adopted the generally prevailing approach reflected in secondary authority and federal cases: courts should uphold the agency’s interpretation so long as it is reasonable, applying a highly deferential lens.

In adopting that rule, the Court expressly looked to the Tenth Circuit’s three-factor framework from S. Utah Wilderness All. v. Off. of Surface Mining Reclamation & Enf't, which evaluates the agency’s interpretation by:

  • examining the entire context of the original order;
  • looking to subsequent agency conduct, especially further orders; and
  • examining the agency’s litigation position.

The Court tied this deference to New Mexico’s established reluctance to second-guess policy-laden Commission decisions and its long-recognized view of the Commission’s breadth in ratemaking.

B. Precedents Cited (and How They Shaped the Decision)

1. Winter Storm Uri context cases (illustrating market conditions)

  • Holcim U.S. Inc. v. Colo. Pub. Utils. Comm'n and Evergy Mo. W. Inc. v. Off. of Pub. Couns. were used to situate Uri as a multi-state crisis producing price spikes and “rate shock,” supporting the reasonableness of amortization and the Commission’s focus on reliability and cost-effectiveness.

2. Proxy pricing’s legitimacy in utility regulation

  • Transmission Agency of N. Cal. v. FERC supported the proposition that proxy prices deviating from market price can still be “just and reasonable” if supported by record evidence—reinforcing that proxy mechanisms are not inherently unlawful.
  • Pub. Serv. Co. of N.H. v. Patch illustrated proxy pricing in restructuring contexts, underscoring that regulators sometimes use proxies to implement policy goals rather than strictly track embedded costs.

3. New Mexico administrative law standards (burden, review, and Commission discretion)

  • N.M. Indus. Energy Consumers v. N.M. Pub. Regul. Comm'n (2019-NMSC-015) supplied the appellant’s burden and the “arbitrary and capricious” / “substantial evidence” standards.
  • Pub. Serv. Co. of N.M. v. N.M. Pub. Regul. Comm'n framed how the Court distinguishes questions of law and fact and when “heightened” deference may be appropriate for agency-expertise policy questions.
  • N.M. Atty. Gen. v. N.M. Pub. Regul. Comm'n was cited for the “whole record” view of arbitrary-and-capricious review.
  • N.M. Indus. Energy Consumers v. N.M. Pub. Regul. Comm'n (2007-NMSC-053) and Att'y Gen. of N.M. v. N.M. Pub. Serv. Comm'n emphasized the Commission’s broad ratemaking authority and discretion, including the Court’s recognition that “the Commission is statutorily and constitutionally free to use any ratemaking formula it chooses.”
  • El Paso Elec. Co. v. N.M. Pub. Regul. Comm'n (2025-NMSC-009) provided the Court’s analogical foundation: when issues are policy-centric, the Court “tread[s] lightly” and overturns only if the agency is “clearly incorrect.” The Court extended that stance from ambiguous statutes to ambiguous orders.
  • U.S. W. Commc'ns, Inc. v. N.M. State Corp. Comm'n supported the notion that commission orders can function with statute-like force—supporting the importance (and durability) of the Commission’s prior PV3 proxy price orders.

4. Out-of-state / federal deference-to-orders cases (core support for the new standard)

  • Udall v. Tallman anchored the principle that courts “must . . . respect” an agency’s reasonable interpretation of its own orders, even if other readings are possible (noting it was “superseded by statute on other grounds as stated in W. Energy All. v. Salazar”).
  • City of Angels Broad., Inc. v. FCC was cited for the narrowness of review: courts should not overturn the agency’s construction absent “compelling indications that it is wrong.”
  • S. Utah Wilderness All. v. Off. of Surface Mining Reclamation & Enf't supplied the structured three-factor method the Court embraced.

5. Ancillary citation on law/fact framing

  • Oscar Gruss & Son, Inc. v. Hollander was used to explain that while the amount of damages (or costs) may be factual, the measure/method used to compute them can be a question of law—supporting the Court’s willingness to reach the City’s “monthly” argument on the merits.

C. Legal Reasoning

1. Why high deference (doctrinal justification)

The Court treated the standard-of-review question as “decidedly policy-centric.” Because agency orders can be technical, interlocking, and implemented over time through subsequent orders and practice, the Court concluded that an agency is best positioned to explain what its own orders meant—so long as its interpretation is reasonable.

2. Application to the PV3 proxy price dispute

The City’s primary theory was that language in the 2009 settlement stipulation limiting application to “this Stipulation only” barred continued use of the proxy price. The Court rejected this “freeze-frame” approach by focusing on the Commission’s subsequent orders continuing and reaffirming proxy pricing for PV3:

  • The Court emphasized that the Commission’s 2009 final order described EPE’s agreement “for the period of the Stipulation and until the Commission establishes new rates thereafter,” undermining the City’s attempt to treat the proxy as strictly time-limited.
  • In Final Order, El Paso Elec. Co., No. 13-00380-UT, the Commission expressly approved EPE’s application “to continue the current proxy price” and found it “continue[d] to be reasonable,” concluding that even if the earlier agreement terminated, “the associated pricing remain[ed] competitive” and reflected “the lowest equivalent market price.”
  • In Final Order Adopting Recommended Decision with Modifications (Final Order), El Paso Elec. Co., No. 18-00006-UT, the Commission maintained the proxy-price status quo and expressly signaled that broader proxy-pricing reforms should occur in a future rate case, not via the FPPCAC review.
  • The Commission later characterized the 2019 order as the “relevant” order in effect during the Uri period and as “confirm[ing] the continuation” of proxy pricing in Order Denying Motion for Rehearing and Motion for Stay, El Paso Elec. Co., No. 21-00064-UT.

Under the newly adopted deferential review, these subsequent orders and agency practice strongly supported the Commission’s reading that proxy pricing remained authorized during Winter Storm Uri.

3. Arbitrary/capricious and substantial evidence review

The Court also rejected the City’s fallback claims. The Commission framed the decisive factual question as whether PV3 energy and capacity was the “most cost-effective resource” available to EPE during Uri. The Commission adopted the hearing examiner’s findings that: PV3 was necessary and available to provide uninterrupted service, and EPE’s decision to use PV3 during the crisis was “manifestly reasonable.”

Addressing the City’s argument that the proxy price was applied for “Every Hour of February 2021” even though Uri lasted seven days, the Court accepted the Commission’s explanation that the proxy formula is computed “[o]n a monthly basis” by design, and credited testimony that EPE repriced monthly through FPPCAC reporting. The Court further noted testimony that EPE excluded pre- and post-storm days when markets were adjusting, undermining the City’s overbreadth theory.

D. Impact

  • Administrative law in New Mexico: The decision establishes a statewide precedent that New Mexico courts will give high deference to an agency’s reasonable interpretation of its own orders, aligning New Mexico with the dominant federal approach reflected in Udall v. Tallman and City of Angels Broad., Inc. v. FCC.
  • Utility regulation: For NMPRC matters, the ruling makes it harder for challengers to relitigate the meaning of historical, multi-order regulatory frameworks (like the PV3 proxy regime) by isolating a single stipulation clause. Future litigants must engage the “entire context,” subsequent orders, and consistent agency practice—precisely the evidence that tended to favor the Commission here.
  • Order drafting and record-building: Agencies may rely more heavily on interpretive continuity across proceedings, while parties seeking to limit an order’s future application will likely insist on clearer sunset provisions in final orders (not just in settlement language).

IV. Complex Concepts Simplified

  • FPPCAC (Fuel and Purchased Power Cost Adjustment Clause): A ratemaking mechanism that allows utilities to adjust charges to reflect changing fuel and purchased power costs, typically through periodic (often monthly) calculations and allocations.
  • Proxy price: A stand-in pricing method used when regulators choose not to base customer charges on the resource’s actual generation cost. Here, PV3’s “energy component” was priced using a natural gas index (Permian Basin daily index) multiplied by a heat-rate factor plus an added amount for non-fuel O&M, and calculated “[o]n a monthly basis.”
  • Capacity vs. energy: “Capacity” is the value of having generation available to meet demand (priced here as $/kW-month); “energy” is the electricity actually produced (priced as $/MWh).
  • Decertified and deregulated plant (in the New Mexico jurisdiction): PV3 was not included in New Mexico base rates; instead, EPE’s voluntary use for New Mexico load was conditioned on pricing it at a Commission-approved “lowest equivalent market price” proxy.
  • Arbitrary and capricious / substantial evidence: “Arbitrary and capricious” asks whether the agency lacked a rational basis or ignored important factors; “substantial evidence” asks whether credible evidence in the whole record supports the agency’s conclusion.
  • Deference to an agency’s interpretation of its own orders: A reviewing court generally will not substitute its own reading if the agency’s reading is reasonable, especially when subsequent agency orders and practice confirm that understanding.

V. Conclusion

The Court affirmed NMPRC’s approval of EPE’s Winter Storm Uri-related recovery using the PV3 proxy price methodology and, more significantly, announced a new New Mexico standard: courts will apply a highly deferential review to an agency’s interpretation of its own prior orders. The decision strengthens institutional continuity in administrative regimes that evolve through serial orders and reinforces the Commission’s discretion in technically complex, policy-sensitive ratemaking disputes.