By 2025, balancing and flexibility revenues became a profit driver for renewable electricity producers across Southeast Europe. For much of the previous decade, balancing markets in the region were treated as technical necessities rather than commercial trading areas. Renewable generators largely focused on energy volumes and incentive-backed prices, while flexibility value was associated mainly with legacy thermal and hydro operators. That separation changed as wind and solar penetration increased.
As renewable output grew, the ability to manage deviations, ramp generation and respond to system imbalances became monetisable. This added a new earnings layer alongside revenue from energy sales. The shift coincided with growing forecast errors, intraday volatility and balancing costs across much of SEE. The underlying cause cited was that renewable generation growth outpaced grid reinforcement and market design reform.
Imbalance price spreads during stress periods
In 2025, imbalance prices in Romania, Greece and Bulgaria routinely diverged from day-ahead prices by €20–60 per MWh during stress periods. The source data links these divergences particularly to weather-driven events. For producers able to manage their positions actively, the spreads were described as opportunity rather than penalty. This dynamic tied flexibility value to system conditions rather than only day-ahead energy pricing.
Hydropower shifts toward flexibility value
Hydropower operators were identified as the first group to adjust operating strategies toward flexibility monetisation. In Croatia, Bosnia and Herzegovina and parts of Romania, reservoir-based plants moved away from maximising baseload output. Instead, they sought flexibility value by withholding generation during low-price hours. Water was released into evening peaks or balancing windows.
Under this approach, hydro assets captured price premiums of €15–30 per MWh above day-ahead averages. In 2025, the strategy lifted total hydro revenues by 10–18 percent. The increase was reported without raising annual output volumes. The change reflected a shift in how reservoir dispatch translated into market outcomes.
Wind portfolios improve forecast accuracy and nominations
In 2025, renewable portfolios beyond hydro began participating more directly in balancing-related value streams. Wind producers improved forecast accuracy and intraday nomination practices compared with earlier years. In Romania and Greece, wind forecast errors narrowed to 5–7 percent for well-managed fleets. This was down from double-digit levels earlier in the decade.
The reduction in forecast errors lowered imbalance penalties for wind operators. In some cases, it also enabled producers to sell balancing capacity indirectly through aggregation platforms. The change connected operational performance improvements with commercial participation mechanisms available in the region’s balancing arrangements.
Solar monetises flexibility through storage access and regulation markets
The source describes solar as facing a different constraint despite high forecast accuracy. Temporal concentration was linked to system stress, with midday overgeneration and steep evening ramps increasing balancing needs. Producers that combined solar with limited storage or contractual access to flexible hydro were able to monetise this dynamic. In 2025, solar-heavy portfolios with such access captured €3–7 per MWh in net balancing-related revenues.
The reported net revenues came either from avoided penalties or participation in upward and downward regulation markets. The mechanism depended on whether portfolios could offset imbalance exposure through flexible resources or market participation capabilities. This created a balancing-linked income stream alongside energy sales for solar-heavy operators.
Greece’s fast-response role for flexible renewables
Greece was cited as an example of flexibility monetisation beyond hydro as renewable penetration rose. The transmission system operator increasingly relied on fast-response resources to maintain frequency and voltage stability. Dedicated ancillary service markets were described as relatively small, but flexible renewable portfolios participated through indirect mechanisms.
Wind and hybrid assets capable of curtailing or ramping quickly earned premiums during stressed intervals. For some portfolios, this contributed 5–10 percent of total annual revenue. While characterized as modest in absolute terms, the source linked it to negligible incremental cost relative to other revenue drivers.
Romania’s cross-border liquidity and regional portfolio balancing
Romania’s balancing market evolved rapidly in 2025 as cross-border flows with Hungary and Bulgaria intensified. Price volatility increased while liquidity also improved. Aggregated renewable portfolios with access to multiple balancing zones reduced exposure to local congestion and captured value from geographic price spreads.
The practical effect described was shifting balancing responsibility from a single asset to a regional portfolio. For producers, net imbalance costs fell from €4–6 per MWh to €1–2 per MWh. This was equated to a realized price uplift of €3–5 per MWh. The change reflected how portfolio aggregation interacted with cross-border market conditions.
Bulgaria’s solar imbalance outcomes vary by portfolio optimisation
Bulgaria illustrated both risk and opportunity tied to solar expansion patterns. Rapid solar growth created frequent midday surpluses and evening deficits across the system profile described in the source data. Unoptimised producers paid heavily for imbalances, especially during sudden cloud cover events.
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