ARESEP sets auxiliary service tariffs and adjusts tertiary regulation

The Energy Superintendency of the Public Services Regulatory Authority (ARESEP) set the rates for the ancillary services of the National Electrical System (SEN) for the first time through resolution RE-0051-IE-2026, issued on September 28, 2026, and published this Friday, October 2, in Supplement No. 132 to La Gaceta No. 186. The act, processed under file ET-086-2026, resolved 13 oppositions and one supporting intervention presented during the public hearing on September 4, 2026, and set the tertiary regulation reserve rate at ₡256,846.15/MWh, below the ₡282,279.76/MWh proposed in report IN-0090-IE-2026.

This determination applies for the first time the “Tariff Methodology for the Remuneration of Ancillary Services in the National Electrical System (SEN),” approved via resolution RE-0195-JD-2021 on August 17, 2021, and partially amended by resolution RE-0023-JD-2026 on March 11, 2026. The settlement procedure for secondary and tertiary regulation services was approved by the General Regulator via resolution RE-0240-RG-2026 on July 29, 2026, published in Supplement No. 103 to La Gaceta No. 146 on August 5, 2026.

The ex officio study was activated following judgment No. 2026-20831 of the Constitutional Chamber of the Supreme Court of Justice, dated June 9, 2026, which ordered ARESEP to issue the ancillary service rates within two months. The final technical report IN-0115-IE-2026 of September 28, 2026, serves as the basis for the administrative act, signed by Superintendent Mario Mora Quirós.

The three set rates

• Secondary regulation reserve rate: ₡9,020.71 per MWh.
• Tertiary regulation reserve rate: ₡256,846.15 per MWh.
• Interruptible demand rate: ₡43,468.02 per MWh.

The resolution takes effect from its publication in La Gaceta, subject to the transitional provisions detailed below.

Oppositions: CNFL’s warning regarding the electricity bill

The National Power and Light Company (CNFL) warned in its opposition, submitted via official letter 20011236-2026 on September 4, 2026, that if the proposed rate of ₡282,279.76/MWh were maintained with a deviation tolerance of zero, the component associated with tertiary regulation could represent an increase of over 100% in the rate applicable to the end user. The company requested a tariff impact test per distributor.

The San Carlos Rural Electrification Cooperative (Coopelesca) and the Costa Rican Association of Electricity Producers (ACOPE) questioned the Superintendency’s decision to sum the unit tariffs of 23 plants to obtain a single tariff, given that the ICE is the only recognized provider. According to their calculations, a consolidated approach would yield approximately ₡12,946.19/MWh, and the proposed figure would generate annual revenues close to ₡2,595,844 million compared to recognized costs of ₡119,053 million, roughly 21.8 times more.

The Superintendency rejected those arguments: it maintained that it applied equation 3 “in strict adherence” to the methodology and that it is not competent to modify it, as that power belongs to the Board of Directors. It also dismissed the requested impact study, noting that the methodology does not require it.

Other opponents included CEDET, ESPH, Coopealfaro, El Ángel, El Embalse, Hidro Venecia, Caño Grande, Jasec, the ICE, and the User Counseling Office. ESPH alleged information asymmetry in the file, while CEDET requested a comprehensive simulation of the mechanism’s cost before it comes into effect.

Transitory Provisions: tariffs will not be applied immediately

• Twelve months, counted from the day following publication, during which the tariffs will not be applied; these include eight months for system adaptation and a twelve-month trial period for settlement.
• Two months for the approval of the settlement procedure for interruptible demand, a voluntary service.
• Twelve months for the ICE and private generators covered under Chapter I of Law No. 7200 to sign contractual addenda: eight months to sign them and four for their endorsement.

Oversight of ICE, DOCSE, and JASEC

The resolution orders the immediate start of an oversight process for DOCSE as the System and Market Operator, the ICE as an agent of the National Electric Market, and the Administrative Board of the Electric Service of Cartago (JASEC). The objective is to verify the traceability, accuracy, and veracity of operation, maintenance, depreciation, and revalued net fixed asset costs, as well as the legal and economic status of the Toro III hydroelectric plant.

The decision directly impacts the pockets of subscribers: although the tariffs are already set, they will not be charged until the twelve-month transitory period expires, and the Superintendency must first clear any possible double recognition of costs between the ICE generation tariff and the new charge for auxiliary services. The finally published tertiary tariff is nearly 9% lower than proposed in the initial report, but it remains the most sensitive component for distributors and for the electricity bill.

Source: La Gaceta, Supplement No. 132 to La Gaceta No. 186, Friday, October 2, 2026, Decentralized Institutions section — Public Services Regulatory Authority, Energy Superintendency (official reference: RE-0051-IE-2026).