Flexibility is one of the hottest words in energy right now. It is the missing piece to make clean power reliable, affordable, and secure.
In last week’s Friday Feature, we’ve looked at how battery energy storage system (BEES) can help the power system adapt to supply and demand fluctuations in response to short-term signals.
This week, as we prepare to celebrate Global Hydropower Day tomorrow, we shift our attention to another powerful storage solution that can do the flexibility trick: pumped storage hydropower(PSH).
As Belgian classic goes: Pump Up the Jam!
Flexibility: the key for a stable system and cheaper prices
The Power Barometer 2025 confirms that while Europe’s power sector is delivering on decarbonisation, with clean and renewable electricity reaching 74% of the EU’s generation mix, flexibility is not keeping pace.
And without flexibility, the energy transition is at risk. Here’s why:
- It ensures system stability: the surge in renewables on one hand, and the lack of storage, demand response, and smart grids on the other, increases risks of volatility, negative prices, and regional imbalances.
- Lack of flexibility is expensive: grid stability costs have soared from €2bn in 2020 to €7bn today, and inefficiencies like curtailment and price spikes are on the rise.
- Flexibility means resilience: it is not just a technical issue. It’s central to energy security, affordability, and fairness across Europe.
Behind Europe’s clean energy gains lies a growing challenge: managing the variability of renewable generation. In 2024, negative prices occurred 4.5% of the time, as weak demand and insufficient flexibility failed to absorb excess generation.
If only there was a way to store excess power during times of high production…
Pump it up: the flexibility game changer
Turns out, there is – and it is already scalable. It’s called pumped storage hydropower (PSH) and it’s one of the most effective forms of long-duration energy storage available today.
How it works
Last year, Eurelectric’s team had the chance to see first-hand how a pumped storage hydropower plant operates:
- When there is a surplus of electricity generation and demand is low, water is pumped from the lower to the upper reservoirs.
- When demand peaks, the water is released back into the lower reservoir, generating electricity as it flows through turbines.
Batteries are one of the key providers of power system flexibility. Battery Energy Storage Systems store eSince 1972, with a total maximum capacity of 1,089 MW, ENGIE’s Coo power station has played a crucial role in Belgium’s energy mix. But what about the rest of Europe?
More untapped potential
There are 78 pumped storage hydropower projects across the EU + Norway, Switzerland and Türkiye. But how much storage capacity are we talking about? Combined, they have a storage potential of 700 GWh.
To put it into context: that’s more than 10 hours of electricity consumption in Italy and Spain combined. However, many projects are stuck in the approval phase.
What Eurelectric is doing
The power sector has no intention of missing this opportunity: this is why it partnered with the International Hydropower Association (IHA) for the Paris Pledge initiative.
With 14 signatories representing the entire European hydropower value chain, this pledge presents a series of actions that the hydropower sector and policymakers collectively need to undertake to solve the existing electricity storage and infrastructural gaps and support the rapidly evolving electric power systems.
Key Actions of the Paris Pledge
- Launching a dedicated EU initiative to accelerate electricity storage.
- Treating long-duration storage as a separate priority from short-term solutions in all legislation.
- Swiftly implementing the Renewable Energy Directive (RED III) and the Market Design Reform.
- Ensuring full and timely rollout of recent European energy directives and reforms.
- Paying fairly for the system services and security of supply that pumped storage provides.
- Removing double grid fees on storage to improve economic viability.
These points were delivered to the European Commission during a roundtable with the Paris Pledge signatories.
“As we scale up wind and solar at unprecedented speed, we must invest in long-duration storage solutions that keep the system reliable, affordable, and resilient. Pumped storage hydropower is indispensable here. The Paris Pledge is a timely and necessary call to action – and Eurelectric is proud to support it.” – Kristian Ruby, Secretary General of Eurelectric
Conclusion
As Europe continues to expand wind and solar generation, long-duration energy storage will be essential to balance supply and demand, stabilise markets, and cut dependence on imported fossil fuels.
On the occasion of Global Hydropower Day, it’s a fitting moment to recognise the enduring contribution of hydropower to Europe’s clean energy journey – and the role it will continue to play in shaping a resilient, renewable future.
This blog post was originally published as part of Eurelectric’s LinkedIn Friday Features. Subscribe here to stay updated and never miss an edition.
Disclaimer: This article is for communication purposes only and may not reflect Eurelectric positions. Any positions taken in this article shall not be attributable to Eurelectric’s official positioning. Official Eurelectric positions are reflected only in position papers published here.