ANU finds AEMO's electricity grid modelling hides value of energy storage in 100% renewable scenario – and favours gas

An ANU study shows that, in a modelled 2050 Australian grid, long-duration pumped hydro paired with batteries can replace gas in a 100% renewable electricity system at similar cost. Additionally, by examining 17 institutional energy plans from around the world, Tim Weber and Professors Kylie Catchpole and Andrew Blakers and other researchers from the ANU Centre for Energy Systems identified modelling practices that can hide this alternative.

Published in Cell Reports Physical Science, the ACAP-supported study informed ANU’s submission to AEMO’s Draft 2026 Integrated System Plan. The findings were also presented to an influential group of energy leaders and policy makers at Parliament House, including the Minister for Climate Change and Energy Chris Bowen; MPs Helen Haines, Allegra Spender, Andrew Wilkie and Monique Ryan; Senators Wendy Askew and Anne Urquhart; CEO of Clean Energy Council Jackie Trad, Chair of the International Hydropower Association Malcolm Turnbull and Climate Change Authority Chair Matt Kean.

Tim Weber (ANU) presenting at the Australian Hydropower Breakfast at Parliament House in February 2026, with Malcolm Turnbull in the foreground.

The Minister for Climate Change and Energy Chris Bowen at the Australian Hydropower Breakfast at Parliament House in February 2026.

Attendees at the Australian Hydropower breakfast at Parliament House heard from Tim Weber about his ANU study that shows that, in a modelled 2050 Australian grid, long-duration pumped hydro paired with batteries can replace gas in a 100% renewable electricity system at similar cost.

Tim Weber discussed energy modelling and long duration storage with MPs and clean energy leaders. Seen here with Helen Haines MP and others.

International Hydropower Association Chair and former Australian Prime Minister Malcolm Turnbull said, “This research is vital, showing that when you value long-duration assets properly, pumped storage can firm solar and wind seamlessly in line with current costs.”

“This research is vital, showing that when you value long-duration assets properly, pumped storage can firm solar and wind seamlessly in line with current costs.” – Malcolm Turnbull, International Hydropower Association Chair

Weber and team found that common modelling choices can favour gas over long-duration storage. Some methods for simplifying time-series data limit storage to daily cycling, making it difficult to represent storage that can carry energy across several days. Plans may also underestimate off-river pumped hydro potential and focus on only a small number of least-cost pathways.

The ANU team used a time-series simplification method that better captures long-duration storage and developed a framework to explore millions of feasible grid configurations. In its Australian National Electricity Market case study, the modelling found near-optimal 100% renewable pathways using short-duration batteries and long-duration pumped hydro with 48–160 hours of storage.

One pathway included around 1,200 GWh of new pumped hydro, with an average storage duration of about 75 hours. Given the high uncertainty when modelling the grid 25 years in advance, these near-optimal pathways have the same cost as the gas-dependent pathways. The storage technologies play complementary roles: batteries provide short-duration flexibility, while pumped hydro can help balance supply through prolonged periods of low solar and wind generation, including challenging winter weeks. The findings show that how planners represent storage, costs and available sites can determine whether clean alternatives to gas appear viable in their models.

Lead author Timothy Weber said, “We’ve been able to show why energy planners need to look beyond a single modelled pathway. When long-duration storage is properly represented, pumped hydro and batteries can provide a cost-competitive alternative to gas in a 100% renewable Australian electricity system.” 

“Our aim is to give planners and policy makers a stronger evidence base to assess that option and make decisions that support a reliable, lower-emissions grid.” – Timothy Weber

“AEMO and governments need to look beyond gas and support long-duration storage—because projects such as pumped hydro can take up to a decade to build.”

“If gas generators are used more than expected, we risk higher costs and emissions. Long-duration pumped hydro paired with batteries offers a clean alternative that energy planners should investigate more seriously.”

The research supports ACAP’s mission to advance ultra-low-cost solar by addressing a key system-level challenge: how to balance solar and wind when generation is low or demand is high. 

Timothy Weber presented the work at the Australian Hydropower Breakfast at Parliament House on 10 February 2026, attended by Professor Andrew Blakers (ANU) and prominent policymakers and energy leaders including Minister for Climate Change and Energy Chris Bowen; MPs and former MPs Helen Haines, Allegra Spender, Andrew Wilkie, Monique Ryan, Jackie Trad and Malcolm Turnbull; Climate Change Authority Chair Matt Kean; Senator Wendy Askew; and Senator Anne Urquhart. 

The gathering also included International Hydropower Association board members, Snowy Hydro CEO Dennis Barnes, Hydro Tasmania CEO Rachel Watson, and Mike Kaiser, Secretary of the Department of Climate Change, Energy, the Environment and Water.

The study also informed the Centre’s submission to AEMO’s Draft 2026 Integrated System Plan, where the researchers proposed a Long-Duration Energy Storage Options Report to assess promising sites and test how including them in development pathways could reduce system costs. By bringing these options into view, the research gives energy planners evidence to consider alternatives to gas – and helps ensure the potential of solar is assessed alongside the storage needed to support it.

Reference: Weber, T., Cheng, C., Armstrong-Thawley, H., Catchpole, K., Blakers, A., Lu, B., Zhao, J., and Nadolny, A. (2026). Replacing gas with low-cost, abundant long-duration pumped hydro in electricity systems. Cell Reports Physical Science 7, 103523. https://doi.org/10.1016/j.xcrp.2026.103523