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- Surge in solar PV capacity
- Widening spreads between day-ahead and imbalance settlement prices
- Rising intraday volumes
- Solar Nowcasting: How earlier forecasts reduce imbalance costs
- Continue the conversation
Central and South-Eastern Europe (CSEE) is one of the fastest-moving power markets on the continent right now. Rapid solar rollout is driving wider spreads between day-ahead and imbalance settlement prices, which, in turn, are pushing more participants into the intraday market to manage the resulting risk.
If you’re trading short-term power in the region, these trends are likely shaping your P&L. Last week at the Energy Trading Central and South-Eastern Europe conference (ETCSEE), we delivered a talk on power trading in Romania, Hungary, Bulgaria and Greece. We outline the main points below.
Surge in solar PV capacity
Between 2022 and 2025, CSEE added 20.5 GW of solar PV. Greece led in absolute terms, growing from 5.5 to 11.5 GW (+6.0 GW). Romania was the fastest-growing market, with a 57% CAGR, roughly quadrupling its installed capacity from 1.9 to 7.2 GW. Bulgaria and Hungary each added around 4.2–4.3 GW over the same period.
The mix isn’t uniform across the region. Greece is the most solar-dominated system, and its imbalance is heavily a midday and solar-ramp story. Romania carries significant wind alongside its new PV – a mixed renewable profile that changes the timing and shape of imbalances. Bulgaria started the period with 1.7 GW and has grown fast. Hungary runs a high solar share relative to its system size, with limited domestic flexible capacity to absorb swings.
When you add this much intermittent generation this quickly, the system struggles to balance it. Forecast errors get larger and more frequent. That’s what widens the gap between what you plan day-ahead and what you actually settle at in imbalance.
Widening spreads between day-ahead and imbalance settlement prices
The absolute day-ahead-to-imbalance (DA-IMB) spread is a useful proxy for imbalance price risk. Imbalance costs are roughly the price spread multiplied by the incorrectly forecast volume. The wider the spread, the more expensive every single MWh of forecast error becomes. Below, we illustrate the spreads across the four analyzed countries by showing the 12m rolling average to control for seasonality.
Romania stand out this picture. The spread peaked at around 600 EUR/MWh in mid-2025, then came down and is now approaching 2024 levels again. The most likely explanation is that the system was hit by a fast solar rollout before market participants and infrastructure caught up. As the market matures – more flexible capacity coming online, forecasting improving – the spread compresses.
Romania is so dominant here that the other countries are flattened along the bottom. In this next chart, we remove Romania so we can actually review the rest:
Hungary has maintained DA-IMB spreads consistently above 100 EUR/MWh for three years. It leans heavily on imports and cross-border flows, and limited domestic flexibility keeps imbalance risk structurally elevated. There are no extreme peaks like Romania, but spreads are consistently high.
Bulgaria shows the clearest regulatory story. Under the old dual-pricing system, imbalances were penalized asymmetrically. After Bulgaria switched to single pricing in 2024, the spread flattened. Bulgaria also has a significant BESS pipeline, with capacity starting to come online, so it will be worth watching whether spreads compress as a result.
Greece remains contained, largely due to its imbalance price floor. Before mid-2025, the floor effectively prevented prices from going negative, limiting how wide the downside spread could get. In mid-2025, the floor was reset to -50 EUR/MWh, allowing modestly negative prices. Still, the floor mechanically constrains the spread relative to Hungary and Bulgaria, even though Greece has the most solar in the group.
Our takeaway is that elevated imbalance risk is a region-wide feature. The drivers vary by country – fundamentals, market design, and emerging flexibility – but no market is immune.
Rising intraday volumes
Intraday volumes in CSEE have grown 4.5x, from roughly 20 GWh per month in May 2023 to around 90 GWh per month in May 2026. Romania, Bulgaria, and Greece all contribute to that growth. Hungary is not separately reported.
The split by country reflects market maturity. Romania and Bulgaria are the heavier intraday users: BRPs there increasingly use the intraday market to correct and close imbalance positions before delivery, precisely because the cost of getting it wrong is so high. Greece has a thinner, less mature intraday market, contributing less to volumes despite having the most solar.
Solar Nowcasting: How earlier forecasts reduce imbalance costs
The trends above point to a renewable energy forecasting gap, one we’ve built our products specifically to close. The better you can predict solar output and the earlier you can see deviations coming, the smaller your imbalance exposure.
At ETCSEE, we highlighted our Solar Nowcasting, a proprietary forecast that ingests satellite data every 15 minutes at 4x higher spatial and temporal resolution than standard numerical weather prediction (NWP) models, and produces updated solar forecasts up to 4 hours ahead of standard models.
To illustrate what that edge is worth in practice, we extracted a real-world case study: 10 April 2026 in Romania. By 07:00 on this day, dense cloud bands had spread across the country. However, ECMWF’s 00:00 run had underestimated both their extent and intensity, so BRPs positioned accordingly. Dexter Nowcasting, however, tracked the cloud bank hours earlier.
The forecast error showed up in the imbalance price, which peaked at €1,189/MWh at 09:00 and €1,154/MWh at 09:15. A BRP with access to our signal at 07:00 could have acted before the market did, closing their short position on intraday at around 125 EUR/MWh. Those without it were caught out when the imbalance price spiked. On a 10 MW position, that failure to act cost 5,200 EUR over those two quarter-hours.
Continue the conversation
Solar pipelines across all four markets are still filling, and Bulgaria’s BESS capacity is only beginning to come online. The spread and volume picture across CSEE will continue to shift; we’ll be publishing updates as the data develops, so follow us on LinkedIn to stay informed.
If the trends above are relevant to your portfolio, we’d welcome a conversation.