Europe faces significant challenges in meeting energy demand during winter due to limited solar availability in its northern latitudes. A fully decarbonized Europe will depend heavily on solar power from the south, wind energy from the north, and, critically, large-scale, long-duration energy storage systems to bridge days or even weeks of low renewable generation. Among storage solutions, PHES (pumped hydro energy storage) stands out as the most viable and cost-effective long-duration option.
PHES currently accounts for 95% of the world’s long-duration energy storage capacity, typically measured in gigawatt-hours (GWh). It complements battery storage, which is ideal for short-term, high-power applications (in gigawatts). Together, batteries and PHES can address the full range of storage requirements needed for a resilient renewable energy grid.
Europe has abundant potential for PHES, particularly in off-river sites, which do not require the construction of new dams on rivers. This counters the common misconception that PHES entails large-scale environmental disruption. The global pumped hydro atlas identifies over 820,000 potential PHES sites worldwide, with more than 6,000 premium-quality locations in Europe alone. These premium sites offer large storage capacities (over 40 GWh), long durations (over 100 hours), high elevation differences, and minimal environmental footprint. Europe’s available PHES potential—estimated at 1,100 terawatt-hours—is approximately 40 times more than what is needed to fully decarbonize and electrify the continent.
Capital costs for premium PHES sites range from $8–25 per kWh. For example, Australia’s Snowy 2.0 PHES project, with 350 GWh of storage capacity and 2.2 GW of power, has a cost of US$22/kWh. This is far more economical than battery storage when considering systems designed to last 100 years.
Alternative storage options such as clean hydrogen face challenges due to low round-trip energy efficiency and high electrolysis costs. While hydrogen is important for producing fuels and chemicals, it is less effective for electricity storage compared to PHES.
Importantly, PHES systems require minimal land and water. A hypothetical 5,000 GWh site serving 100 million people would flood only 60 km² of land—much less than solar farms or parking lots for an equivalent number of electric vehicles. Water use is also modest since the same water is recycled within the system, with only small amounts needed to offset evaporation over time.
Contrary to outdated assumptions, PHES does not necessitate massive land disruption, river damming, or high operational costs. The use of off-river sites minimizes environmental impacts, and strong European transmission networks enable energy and storage sharing across regions, reducing local storage needs. Hybrid systems that combine PHES for energy storage and batteries for power delivery offer both economic and operational efficiency, allowing trickle-charging during low-price periods.
As Europe accelerates its transition to renewable energy, with solar and wind being deployed at record rates, the demand for robust, scalable energy storage solutions will only grow. Thanks to its low cost, long lifetime, and minimal environmental footprint, PHES is positioned to be the backbone of a reliable, clean European energy system.
www.pv-magazine.com/2025/03/14/unlimited-energy-storage-in-europe