ACER Calls For Better Market Modelling As Data Centre Demand Outpaces Electricity Supply In Portugal

ACER published its Opinion on Portugal’s National Resource Adequacy Assessment (NRAA).

The NRAA is part of the country’s electricity security of supply monitoring report and complements the European Resource Adequacy Assessment (ERAA) 2025.

What is a resource adequacy assessment?

The ERAA assesses whether the EU has enough electricity resources to meet demand and ensure security of supply. It is carried out annually by the European Network of Transmission System Operators for Electricity (ENTSO-E) and reviewed by ACER.

Member States can complement this European analysis with national assessments (NRAAs) that reflect local conditions. When a national assessment differs from the European one, ACER issues an opinion.

What did the Portuguese NRAA find?

Unlike the ERAA 2025, which found no adequacy concerns for Portugal, the national assessment identified adequacy risks in all target years from 2028 to 2035.

The NRAA assumes electricity demand growing much faster than the resources needed to meet it, driven mainly by data centres, slower renewables deployment, reduced pumped-hydro availability and conservative battery rollout.

What are ACER’s key findings?

ACER finds that the projected adequacy risks are largely driven by assumptions of strong demand growth, while new capacity, including demand-side response, is assumed to lag behind. The NRAA:

Does not adequately assess how the market could respond to increasing electricity supply scarcity: it shows that existing gas-fired generation would remain highly profitable as prices rise, but does not examine what new investments this could attract.
Overlooks cross-border factors, such as Spain’s recently approved capacity remuneration mechanism, that could affect Portugal’s electricity imports during scarcity.

As a result, the assessment may overestimate Portugal’s adequacy gap.

What does ACER recommend?

To strengthen Portugal’s assessment, ACER recommends:

Applying the economic viability assessment in line with the ERAA methodology.
Assessing the potential for new market-based investments, particularly batteries and demand response.
Reflecting the contribution of currently ‘out-of-market' resources.
Using more realistic demand response projections.

What are the next steps?

ACER encourages the Portuguese authorities to consider its feedback to improve the assessment.