ReHydro Modernisation Survey: Empirical Insights Into European Hydropower Refurbishment Practice

Abstract

As European power systems face a doubling of flexibility requirements by 2030, the continent’s hydropower fleet requires modernisation to deliver enhanced flexibility. This paper presents the ReHydro Modernisation Survey, capturing responses from 46 power utilities representing 121 GW of hydropower installed capacity (47% of European capacity) across 24 countries.

Findings reveal 24% of the European fleet underwent some degree of modernisation in the past decade, with a stable modernisation trend expected to continue, prioritising performance, reliability and operational safety. Keeping assets productive seems to be the main driver, with energy production driving 70% of investment rationales. Market and revenue uncertainties, together with re-licensing constraints, emerge as primary barriers, increasing project complexity and extending timelines.

To deepen these quantitative findings, a dedicated utility workshop with survey participants was organised to discuss and refine the results. The discussions provided a forward-looking view of modernisation strategies, highlighting three main directions: maturing short-term markets are expected to drive more investment in flexible operation; the water-energy nexus (drinking and industrial water supply, irrigation, ecosystems, flood control, drought management, etc.) will become more critical for some sites; and environmental enhancements (fish migration, habitat conditions, sediment management, biodiversity preservation etc.), already central to around 10% of project costs in the surveyed portfolio, are expected to grow in importance.

The survey highlights a growing mismatch between hydropower’s system-critical role in providing longterm energy flexibility and the limited market remuneration currently available. These findings underscore the need for appropriate investment incentives and re-licensing frameworks that reward modernisation. This study aims to equip operators, TSOs and policymakers with comprehensive empirical evidence to support Europe’s energy transition into a flexible, renewable system.

Quentin Boucher, SuperGrid Institute; Matteo Bianciotto, IHA; Brandon Marler, IHA; Benjamin Graff, CNR – Compagnie Nationale du Rhône;  Martin Boden, ALPIQ; Yann Le Cahain, ALPIQ; Lee Estrellado, vgbe; Atle Harby, SINTEF Energy Research.

Presented at HYDRO, Oct 2026, Bologna, Italy.

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