Portugal mandates grid-forming for energy storage systems. A lesson for Poland

The Portuguese government has introduced a new regulation for energy storage developers. New BESS facilities must provide grid-forming capabilities. Furthermore, they must also deliver synthetic inertia. The regulations came into force on 23 October 2026. Portugal has taken a proactive approach, choosing not to wait for the EU to revise its network codes.

Who do the new regulations apply to?

The new regulations apply to all grid connection applications submitted from the date the regulation entered into force. Existing facilities will only be subject to the new requirements if they undergo major modernisation or expansion.

Lawmakers have made the scope of obligations dependent on the installation’s power rating and the voltage level at the connection point:

• Grid-forming and synthetic inertia are mandatory for facilities connected to the transmission grid (110 kV and above) and installations rated at 45 MW or more.
• For projects rated between 10 and 45 MW, the requirement will be determined individually in the grid connection conditions or tender documentation.
• Energy storage systems** rated at 500 kW or more** must automatically switch from charging to discharging if the grid frequency falls below 49.2 Hz.
• Installations rated above 1 MW must provide the grid operator with full real-time monitoring and remote control capabilities.

Traditional pumped-storage hydropower plants, which inherently provide mechanical synchronous inertia, are exempt from the new grid-forming requirements.

Stringent battery performance requirements

The required technical parameters were developed based on guidelines from European industry organisations, including ENTSO-E and SolarPower Europe. Battery systems must maintain a power reserve to provide synthetic inertia during frequency fluctuations ranging from 47.0 Hz to 52.5 Hz.

The inertia emulation time must be adjustable between 1 and 20 seconds (with a default setting of 12 seconds). Energy storage systems must also achieve a power oscillation damping ratio of at least 10%. Gradual load changes must be completed within a maximum of 10 minutes unless the operator instructs otherwise.

Importantly for investors, the regulation gives grid operators the right to intervene during situations that threaten grid stability but does not require BESS owners to permanently reserve a portion of their battery’s state of charge for this purpose.

Accelerating investment in the Iberian Peninsula

The government in Lisbon explains the urgency of these measures by pointing to the need to maintain grid stability amid the rapid growth of wind and solar power capacity. Under its proposed strategy, Portugal aims to achieve 6.9 GW of energy storage capacity by 2030.

Support for this market is substantial. At the beginning of last year, €100 million in grants was awarded to 43 projects with a combined capacity of 500 MW, while further battery capacity auctions are being prepared. Portugal had just 20 MW of operational battery storage capacity. As a result, the entire upcoming investment boom will develop under the new, stringent standards.