Hidroelektrane na Trebišnjici (HET), the hydropower subsidiary of Elektroprivreda Republike Srpske (ERS), produced 690 GWh of electricity in the first half of 2026. Output exceeded its plan by 66 GWh and kept HET as the largest generator in Republika Srpska. Production ran about 10.5% above target. By the end of June, HET had reached 64% of its annual generation plan.
Completed generation and the energy value of available reservoir reserves together accounted for about 85% of the expected annual total. The company’s stronger performance was concentrated in the opening months of the year. Rainfall across the Trebišnjica basin reached approximately 880 litres per square metre. This supported higher inflows and lifted the Bileća reservoir to its highest level of the year on 25 February.
Dry spring affects reservoir management
After February, conditions changed as the March-to-June period became exceptionally dry. Inflows fell below historical averages, prompting more conservative reservoir management by HET. The company is operating amid a pattern of intense short rainfall episodes followed by prolonged dry periods. This contrast is increasing complexity for hydropower scheduling.
The Bileća reservoir is currently at about 371 metres above sea level, around 10 metres below its planned level. Management considers the remaining water reserve sufficient to keep production close to its annual target. Additional precipitation is expected during autumn, which is part of the basis for maintaining output levels.
Dispatch value linked to coal availability
HET’s generation performance also has implications for ERS operations and costs. Hydropower output has low marginal costs and can be dispatched during higher-priced periods. It is particularly relevant when ERS’s coal plants are unavailable or running below plan. In that context, each additional megawatt-hour produced from stored water can reduce reliance on imported electricity or help preserve thermal fuel stocks.
The results also reflect differences between generation volume and hydropower value for system planning. Reservoir operators must balance producing immediately against conserving water for later peak periods or retaining reserves for system security. Strong first-half output supports near-term cash generation for ERS. However, a lower reservoir level can restrict flexibility during late-summer dispatch requirements.
Second-half outlook depends on autumn hydrology
HET’s ability to finish the year above plan will depend on autumn hydrology and the dispatch needs within ERS. The company enters the second half with a sizeable production advantage based on first-half results. At the same time, water conditions are less comfortable than those that supported its first-quarter performance.
