The future of renewable energy depends on storage

Renewable energy is booming. Globally, solar, wind and other renewable sources together generated more electricity than coal for the first time in 2025. This is great news for emissions targets but highlights a growing challenge: renewable energy is not always generated when we need it, so it needs to be stored.

Electricity demand does not necessarily coincide with when the sun shines or the wind blows. This is why energy storage is becoming one of the most important pieces of the clean energy transition.

Pumped storage hydropower (PSH) is by far the world's largest form of long-duration energy storage, providing over 94% of the world's long-duration energy storage capacity. Its ability to store vast amounts of electricity and operate for decades makes PSH one of the most important tools for balancing renewable energy and maintaining reliable power systems.

PSH is nothing new and has been helping balance electricity grids for many decades. But today it is taking on a renewed importance as countries increase their reliance on renewable energy. According to the International Hydropower Associations 2026 World Hydropower Outlook, more than 600 GW of pumped storage projects are currently in development around the world as governments and grid operators look for ways to store renewable electricity and keep power systems stable.

What is pumped storage hydropower? Think of it as being like a huge water battery, with two reservoirs at different elevations. When more electricity is generated than is needed, such as on a windy night or on a very sunny day, this surplus electricity is used to pump water upstream to the upper reservoir. When electricity demand is high, water is released to the lower reservoir, spinning turbines that generate electricity.

PSH also offers several important advantages. Once operational, the water in the system can be reused many times. Systems generally have large capacities, can run for long periods and can react quickly to energy supply and demand, with the time from static state to full load being less than two minutes.

While the basic concept remains the same, increasingly, new applications are expanding where and how pumped storage can be deployed.

Examples include using seawater to reduce dependence on freshwater, underwater systems that use pressure at depth and underground reservoirs using abandoned mines. There are hybrid projects underway such as combining it with floating solar panels or coupling it with hydrogen production. Digital technologies such as AI and digital twins are also adding value, providing advanced monitoring systems and helping to make them more efficient and effective.

What's the catch? Building a PSH facility is no easy task. It requires the right geography, significant investment and construction can take many years. The impact on the environment and local communities must also be taken into consideration.

What's more, rapid technological advances are improving efficiency and expanding their capabilities, but at the same time this is making them more complex, particularly as they integrate with increasingly sophisticated electricity grids. Then there are regulatory issues, such as how they participate in electricity markets as well as the capacity for these newer technologies to work seamlessly with existing systems.

But despite these challenges, more and more they are seen as a powerful solution in the energy storage mix, alongside batteries, hydrogen and others. PSH is expected to become even more important as the share of renewables continues to grow.

Standards as enablers As pumped storage projects become more digital, flexible and interconnected, international standards and conformity assessment will be essential to unlocking their full potential while ensuring they remain safe, efficient and reliable.

But, as an IEC Technology and Trend Report notes, the current standards landscape is fragmented and there is a need for a more comprehensive framework covering the entire life cycle of pumped storage systems, from planning and grid integration to operation, maintenance and digital technologies. It identifies key areas where standardization can support emerging technologies, improve interoperability and help integrate increasingly complex storage systems into modern electricity grids.

By identifying these gaps and future standardization needs, the report provides a roadmap for supporting the next generation of pumped storage hydropower projects and accelerating their deployment worldwide.

This is important if pumped storage hydropower is to continue to play its part in a more sustainable energy future.

Learn more about the future of pumped storage hydropower in the IEC Market Strategy Boards Technology and Trend Report: The future of pumped storage hydropower - Technology innovation and standardization trends (2025-2035).

LINK:	https://www.iec.chThe future of renewable energy depends on storage...
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