Assessment of Prosumer Storage and Vehicle-to-Grid Aggregator Models in Southeast European Electricity Markets

Abstract

Background. Electricity markets in Southeast Europe are moving away from vertical integration and state-run dispatch control, replacing them with short-term trading, balancing of purchases and prosumers engaged in electricity sales. For rooftop PV with a battery, a flexible industrial load or an EV charging fleet, the route into these markets runs through an aggregator, the commercial actor that pools such resources to a tradable size. Purpose. The study aims to assess the economic viability of two aggregator archetypes: prosumer renewable energy source aggregators that pool distributed PV with battery energy storage systems (BESS) capacity, and a vehicle-to-grid (V2G) e-mobility aggregator. Findings. Day-ahead prices of the Independent Bulgarian Energy Exchange (IBEX) for September 30, 2025, are checked against ENTSO-E Transparency Platform data, and combined with the grid’s installed BESS capacity; five Western Balkans systems, where aggregator rules are still taking shape (Serbia, North Macedonia, Albania, Bosnia and Herzegovina, and Montenegro), are then compared. On the reference day, a pooled 100 MW / 200 MWh prosumer portfolio generates roughly EUR 32,000 in gross arbitrage margin before balancing-market revenue or EUR 11.1 million annually at 95% availability over one cycle. A V2G fleet of 10,000 vehicles offers 30 to 72 MW depending on the hour, and its modelled margin of approximately EUR 149 per MWh discharged lands close to the storage portfolio’s EUR 160. Western Balkans systems reach only a fraction of this value, since their aggregators get limited access to balancing and day-ahead platforms. Over the 273 hourly-settled trading days from January to September 2025, the annualised one-cycle margin amounts to EUR 5.7 million, with the reference day at the 98th percentile of daily spreads. Implications. Gross unit margins are close, EUR 160 against EUR 149 per MWh discharged, and the capital requirements differ substantially: the storage portfolio has EUR 75 million of CAPEX to recover, whereas the V2G aggregator pays only platform costs of EUR 120 per vehicle per year. The Western Balkans constraint remains market architecture rather than capacity. Four secondary regulation actions with no capital cost (independent aggregator licencing, a 1 MW balancing bid size, third-party access to day-ahead exchanges, and standardised V2G grid-connection rules) would put the Bulgarian margin structure within the regional reach.