Ancillary services are regulated mechanisms inherent to the operation of the electricity system. They therefore do not constitute an additional cost, but rather one of the components of the cost of energy. The main components include the costs of resolving technical restrictions, secondary regulation and the active demand response service, with technical restrictions accounting for the largest share.

Ancillary services are costs that generate no revenue for Red Eléctrica. As the transmission system operator, its revenue is regulated by the CNMC and does not depend on or derive from the energy mobilised. During this period, Red Eléctrica's revenue amounted to €70 million, representing 0.28% of the electricity bill, which totalled €25 billion over these eight months. 

The total cost of ancillary services, including the SRAD service paid to its providers, exceeded €3.6 billion in the year to 31 August, 34.5% more than in the same period last year. Of this total, €236 million corresponded to secondary regulation reserves, €286 million to SRAD and €3.1 billion to technical restrictions. 

Technical restrictions are essential measures applied in accordance with regulations to align the market-cleared schedule with system security criteria. They ensure that what the market has previously agreed commercially, without taking into account the laws of physics or regulatory security requirements, can physically be delivered.

The amount paid for technical restrictions is not set by Red Eléctrica. Instead, it reflects the remuneration for the energy offered and supplied by the participants in this mechanism, mainly electricity generators, which receive the resulting revenue. 

Up to 31 August, the energy required to resolve technical restrictions had increased by 33% compared with the same period in 2025, as a result of the significant transformation of the electricity system. However, the cost of these measures for the demand side increased by 43% over the same period, due to the prices offered by market participants. In the first eight months of the year, they offered and received payment for this energy at an average price of €194.85/MWh (weighted average price for upward technical restrictions), compared with the €68.53/MWh arithmetic average price on the day-ahead market.

This trend is not the result of a one-off event. An analysis of the volume of energy mobilised to resolve technical restrictions, both on the transmission grid and distribution networks, and of its total cost since 2021 shows a sustained increase linked to this transformation process. The cost rose from €724 million in 2021 to €1.104 billion in 2022, €1.751 billion in 2023, €2.057 billion in 2024 and €3.347 billion in 2025. It should also be noted that since 2025, reinforced system operation has accounted for only a minor part of the total cost of technical restrictions.

The energy required to resolve technical restrictions has increased in recent years as a result of the profound transformation of the electricity system, driven by a significant deployment of renewable energy and self-consumption, with a particular concentration in certain areas of the electricity system. This trend has introduced new technical challenges for system operation, but it has also made a decisive contribution to decarbonising the electricity system and reducing energy prices for consumers. Over the past four years, since 2023, the addition of 36 GW of new renewable energy capacity and 7 GW of self-consumption connected to the grid has contributed to a reduction of more than 15% in the average final energy price.