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Electrical Energy Storage Systems

1. Self-Generation Plants Combined with Energy Storage Systems

The integration of energy storage systems in self-generation installations (net billing) enables a substantial increase in self-consumption of locally produced energy and a corresponding reduction in energy drawn from the grid.

In practical terms, a photovoltaic (PV) plant combined with an energy storage system can store excess energy generated during periods of high production (e.g. midday hours) and supply it to the consumer’s loads at a later time (e.g. evening hours), when PV production is limited or absent. This operation reduces reliance on grid electricity, resulting in direct economic benefits for the self-generator.

Further improvements in self-consumption can be achieved through smart load management, i.e. shifting the operation of energy-intensive loads in time so that their consumption coincides with PV generation.

In addition, energy storage systems enable energy arbitrage strategies, such as charging during low-price periods and discharging during high-price periods, where permitted under the applicable regulatory framework.

In zero feed-in installations, the storage system may absorb energy from the grid but is not permitted to inject energy back into it. In contrast, in market-participating installations, both absorption and injection of energy may be allowed, depending on the applicable operational framework.

2. Integration of Storage Units in Existing and New Photovoltaic Parks

The integration of energy storage systems into photovoltaic plants is permitted under specific conditions, depending on the licensing and operational status of each project.

Indicatively, this applies to:

  • Existing plants commissioned after 4 July 2019
  • New plants that have obtained grid connection terms but have not been commissioned as of 1 December 2025
  • New plants that will obtain grid connection terms and conclude a Power Purchase Agreement (PPA), operational support contract, or contract for difference (CfD) / fixed tariff scheme

The minimum usable capacity of the storage systems is defined as at least one (1) hour of the installed capacity of the corresponding photovoltaic plant.

Energy injected into the grid from the storage system is remunerated based on its participation in the electricity market, in accordance with the applicable regulatory and market framework.

Category 11A Plants

Renewable Energy Source (RES) plants with integrated storage, without the ability to charge the storage system from the grid.
A permanent limitation of 60% of the installed PV capacity is applied during the hours 07:00–19:00 each dispatch day, while no such limitation applies during 19:00–24:00 and 00:00–07:00.

Where an operational support contract exists, it remains in force and governs the remuneration of energy injected by the PV units of the plant

Category 11B Plants

RES plants with integrated storage, with the ability to charge the storage system from the grid.

New applications for photovoltaic plants submitted to the network operator are required to include an energy storage system with a minimum usable capacity of one (1) hour of the installed PV capacity.

3. Energy Storage Stations (ESS)

Energy Storage Stations (ESS) are independent facilities that absorb electricity from the grid and supply it back when demand is higher or market prices are more favorable.

These installations operate independently of generation assets, enabling flexible energy management and supporting the efficient functioning of electricity markets.

ESS revenues are primarily derived from energy arbitrage strategies, i.e. charging during periods of low electricity prices and discharging during periods of higher prices.

A prerequisite for the development and operation of ESS facilities is the holding of a storage license, which may be applied for at the Regulatory Authority for Waste, Energy and Water (RAAEY) during the first ten-day period of each month, in accordance with the applicable procedures.

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