Czechia’s “Giant Battery” Hits New Heights: Dlouhé Stráně Breaks Production Record

The Dlouhé Stráně pumped-storage hydropower plant has achieved a historic milestone, reaching its highest monthly production level to date. In March 2026, the facility generated 83.073 gigawatt-hours of electricity, surpassing a previous record set six years ago by nearly 1%. This peak performance serves as a powerful validation of a multi-year, 1 billion koruna (€41 million) modernization initiative. The initiative was recently completed by the Czech utility giant ČEZ.

The facility, which has been in operation for three decades, serves as a massive “underground battery” for the Czech Republic’s energy infrastructure. Its primary function is to stabilise the national grid by storing excess energy. Additionally, it provides a critical “black start” capability—the ability to restart the power system in the event of a total blackout. One of the site’s most impressive engineering feats is housing Europe’s largest reversible water turbine. This turbine boasts a capacity of 325 megawatts.

Much of the recent success is attributed to technical enhancements finalised in 2021. By optimising the upper reservoir, engineers increased its operating volume to 2.72 million cubic metres. This technical adjustment effectively boosted the plant’s production capacity per cycle by roughly 6%. These upgrades at Dlouhé Stráně are a centrepiece of a broader 5 billion koruna (€204 million) investment strategy by ČEZ. The strategy aims to overhaul 20 different hydropower sites across the country, including Lipno and Slapy. Across the entire portfolio, these systematic improvements have increased overall operational efficiency by as much as 10%.

Róbert Heczko, Director of ČEZ Hydropower Plants, noted that the record-breaking output underscores the strategic importance of the site. He emphasised that the combination of rigorous maintenance and forward-thinking modernisation has not only improved the plant’s physical condition but has also ensured its continued relevance in a rapidly evolving energy market. As the Czech grid integrates more variable renewable sources, the flexibility provided by upgraded facilities like Dlouhé Stráně becomes increasingly vital. These upgrades are critical for maintaining a consistent and reliable power supply.