Diamante Hydro Power Plant (‘HIDISA’)

In the province of Mendoza, on the Diamante River, HIDISA operates the Diamante System, which consists of three dams and hydropower plants (Agua del Toro, Los Reyunos and El Tigre). With a 388 MW gross capacity, which represents 0.9% of Argentina’s total capacity, HIDISA extends over around 55 km, and its height ranges between 873 m and 1,338 m above sea level. The average annual generation between 1990 and 2024 was 528 GWh, with a record high of 943 GWh in 2006 and a record low of 303 GWh in 2022. Pampa holds a direct 61% stake in HIDISA.

HIDISA’s concessions expired on October 19, 2024, consisting of one granted by the Province of Mendoza for the use of water resources, and another by the National Government for the use of assets and electricity generation. On October 18, 2024, the Government of Mendoza established a 12-month transition period as from the expiration date (DNU No. 2,096/24). In addition, the National Secretariat for the Coordination of Energy and Mining set the transition period through June 1, 2025 (Res. SECyM No. 1/24). On October 20, 2025, the SE proposed extending HIDISA’s concession until June 2026, subject to Pampa’s adherence to the terms of the original concession agreement and to new conditions, including the update of guarantees, the waiver of claims against the State arising from changes in the remuneration scheme, and the payment of royalties to the Province of Mendoza, among others (Res. SE No. 398/25). On November 19, 2025, Pampa adhered to the proposal, suggesting certain modifications which, to date, have not been challenged, and extended operations until July 2026.

On March 8, 2025, the National Government and the Province of Mendoza agreed to jointly tender the HIDISA and HINISA concessions as a single business unit. The Agency for the Transformation of Public Enterprises was appointed to coordinate and conduct the tender process within 60 business days. As of the date of this annual report, the tender schedule has not been published.