Pumped storage accounts for over 94% of installed global energy storage capacity, rightfully deserving the accolade of being the world’s ‘water battery’. The existing 161,000MW of pumped storage capacity supports power grid stability, with the International Hydropower Association (IHA) estimating that total storage is in the region of 9000GWh.

A recent IHA working paper on pumped storage has been produced to help stimulate timely discussion among policy makers and energy system stakeholders about the increasingly important role of pumped storage in the clean energy transition. The paper provides an assessment of the technology’s current status as well as tracing its historical roots.

After WW2

Although first developed at the turn of the 20th century, planning and construction of pumped storage projects didn’t begin in earnest until after the end of the Second World War. As the IHA states, significant post-war population increases and rapid economic growth reshaped demand curves by increasing the peak-to-baseload ratio and creating more distinct seasonal peaks. Pumped storage became increasingly attractive as part of multipurpose projects, where it enhanced the economics of each objective.

By the 1960s, most of the new thermal generators coming online were best suited for constant high output in order to reduce equipment stress and maintenance cost while optimising operating efficiencies. Pumped storage plants were ideally placed to absorb surplus power and generate peaking capacity and were almost exclusively built by state-owned utilities. Many of these projects were also designed to offer water management co-benefits, with pumped storage in California and later South Africa being used for significant water transfer and supply schemes to major demand centres.

The majority of pumped storage projects were built between the 1960s and 1980s and were driven by energy security concerns and nuclear energy development after the oil crises in the 1970s. Fewer projects, especially in the more mature markets of Europe, Japan and the US, were developed in the 1990s; the main reason for the reduction was a result of energy market deregulation and a decline in nuclear growth.

However, there were some exceptions. For example, Austria didn’t have any nuclear generation but a rich hydropower resource, and so developed pumped storage to enhance the operation and efficiency of its large-scale hydropower fleet and balancing services to neighbouring grids. Meanwhile Norwegian pumped storage was developed for seasonal balancing.

Since the turn of the century, there has been a renewed interest in a number of other countries in Europe and virgin markets, but most notably in China. Indeed, China has contributed to much of the recent growth having added nearly 15,000MW of capacity alone since 2010, driven by ambitious government targets for renewables.

Looking forward

Looking forward to 2030, installed capacity is expected to increase by some 78,000MW. Again, much of this growth is expected to take place in China (up to 50,000MW). The main driver for pumped storage expansion in China is the increased need for system flexibility, particularly the need to reduce wind and solar PV curtailment.

In Europe, capacity is expected to grow modestly, between 8-11,000MW by 2030, driven by the need for increased flexibility due to variable renewable energy growth. Most additions in Europe are expected in Switzerland, Austria, UK, Portugal and France, while some prospective projects in Romania, Ireland and Ukraine may also go ahead.

Outside of China and Europe, the majority of pumped storage additions are expected to occur in the Asia-Pacific region, with some notable additions in non-traditional markets in the Middle East. India, Indonesia, the Philippines and Thailand all have projects in the pipeline. In Australia, the federal government has announced support for numerous schemes, notably the 2GW Snowy 2.0 project, in order to balance higher shares of renewables and the expected retirement of existing baseload coal generation. Projects under construction in Israel, Morocco and Iran are expected to add nearly 1000MW, while the UAE and Egypt have also recently announced plans to add pumped storage to their grids.

The IHA goes on to add that a vast potential for further pumped storage development across the world exists, and a number of countries have mapped this potential. In Australia a recent study identified 22,000 potential sites with a storage potential of 67TWh. The vast majority of these sites were off-river and the study concluded that in order for the country to transition to a 100% renewable electricity grid, only the best 20 sites would need to be developed.

Non-powered dams also represent great untapped potential: it is estimated that 12,000 MW of capacity could be added from this source in the US, and some of which could be used for pumped storage. The Los Angeles Department of Water and Power is considering equipping the Hoover Dam with a pipeline and a pump station.

World Congress

In order to advance the development of pumped storage projects, the IHA suggests that the following areas which would benefit from further investigation and discussion, and will be focused on during its 2019 World Hydropower Congress. These include:

  • Identifying what policies, regulatory frameworks, permitting regimes and grid charging structures have proven to be most successful in incentivising and adequately rewarding private sector pumped storage development.
  • Developing case studies which highlight the complementary roles that pumped storage and batteries can provide in the energy transition.
  • Further research and analysis on how much energy is currently stored in pumped storage reservoirs around the world.
  • Evaluating the system scale greenhouse gas benefits of pumped storage at increasing levels of variable renewable energy penetrations and how that compares to other electricity storage options.



The IHA working paper The World’s Water Battery: Pumped Hydropower Storage and the Clean Energy Transition was published in December 2018. The authors were Mathis Rogner and Nicholas Troja with support from David Samuel and Samuel Law.

The pumped storage working paper draws on data available from the IHA’s Hydropower Pumped Storage Tracking Tool which is described as being the most comprehensive and up-to-date online resource of the world’s water batteries. Developed in 2017, the tool shows the status of a pumped storage project, its installed generating and pumping capacity, and its actual or planned date of commissioning. For information email Mathis Rogner, Senior Hydropower Analyst  mr@hydropower.org

The IHA’s seventh World Hydropower Congress will be held in Paris from 14-16 May 2019. The event will be hosted in partnership with UNESCO’s International Hydrological Programme and will focus on hydropower’s role in delivering the Paris Climate Agreement and the Sustainable Development Goals. The theme is The Power of Water in a Sustainable, Interconnected World.

A focus session on pumped storage will be held on Wednesday 15 May. Study tours of interest for those looking at pumped storage schemes will include visits to Vianden pumped storage plant in Luxembourg; the Nant de Drance hydropower plant and Forces Motrices Hongrin Léman power station in Switzerland; and Grand’Maison dam in France.