Long-duration storage could replace gas at similar cost

Estimated reading time: 5 minutes · Last updated: 29 September 2026

A team at the Australian National University, led by Timothy Weber, demonstrates that long-duration storage—predominantly pumped hydro—can operate the National Electricity Market without fossil gas at roughly the same total cost. They ran an unsimplified simulation using a modelling technique called segmentation and corrected outdated assumptions about pumped-hydro costs and deployment potential; this produced a pathway that includes about 1,200 gigawatt-hours of new pumped hydro. The finding challenges model-driven preferences for gas and points to a substantially larger pumped-hydro build than is currently in the pipeline.

Why common modelling shortcuts favour gas

Planners build long-term electricity scenarios by simplifying decades of weather and demand data so runs finish in a practical time. The ANU team compared several simplification techniques against a full, unsimplified simulation and found most shortcuts bias results toward gas because they under-represent rare but important long-duration low-renewable periods.

One modelling approach — the segmentation method the authors used as a benchmark — captured those prolonged dry or low-wind sequences better than the popular shortcuts. When storage is tested against a realistic spread of weather and demand, expensive, high-capacity seasonal storage options become more valuable and gas less so. The researchers therefore argue the apparent need for ongoing gas in many published plans is a modelling artefact rather than a physical inevitability.

What the pumped-hydro assumptions changed

The paper revisited two inputs that materially affect cost outcomes: how much pumped hydro can be built, and how cheaply it can be delivered at scale. Updating those assumptions moves pumped hydro from a niche reserve option to a central, affordable provider of long-duration storage.

With the revised inputs, the modelled system depends on about 1,200 gigawatt-hours of new pumped hydro. That scale drives the conclusion that a gas-free mix is cost-competitive, because pumped hydro provides multi-day and seasonal balancing at lower system cost than older, more conservative cost and deployment assumptions would imply.

How much extra wind and solar does a gas-free grid need?

Removing gas from the generation stack does not mean a massive surge in wind and solar beyond current practice. The ANU scenarios require, on average, an additional 670 megawatts of solar and 370 megawatts of wind per year compared with a pathway that retains gas. The authors note those increments are a small fraction of Australia’s recent annual build rates, implying capacity additions are feasible alongside a large pumped-hydro programme.

Those additional renewables reduce reliance on stored energy by meeting daytime and windy-period demand directly; pumped hydro then covers prolonged low-renewable stretches. In the modelling, the paired increase in supply and storage is what produces cost parity with gas-based options.

Why batteries alone fall short for multi‑day needs

The researchers contrast fast-response batteries with long-duration pumped hydro. Batteries already dominate frequency-control ancillary services in the National Electricity Market — supplying about 66% of those services, versus roughly 11% from hydro and less than 1% from gas — but multi-day and seasonal balancing requires much larger energy stores per site than utility-scale lithium-ion batteries typically provide.

In other words, batteries are excellent for short-duration stability and fast ramping, but the study shows they are not a practical sole replacement for the deep, multi-day energy capacity that pumped hydro can provide at system scale.

The practical gap between modelling and delivery

A central practical obstacle the paper highlights is the mismatch between modelled needs and current project pipelines. Researchers estimate the existing pumped hydro pipeline at about 192 gigawatt-hours — a long way from the roughly 1,200 gigawatt-hours the zero-gas scenarios rely on. That gap is the single clearest barrier to realising the cost parity the models now show is possible.

Bringing models and policy into alignment will require planners to revisit cost and siting assumptions, accelerate candidate-site assessment, and address permitting, grid connection and finance at larger scale. The paper’s finding is a technical prompt to decision-makers: rework the models first, then the procurement and development programmes can be redesigned to match the system the models indicate is affordable.

Case for and against rapid pumped-hydro scale-up

The bottom line

ANU's analysis reframes the technical debate: when models incorporate multi-year weather variability and adopt updated pumped-hydro cost and build assumptions, a gas-free Australian grid looks achievable at comparable system cost. The arithmetic depends on delivering about 1,200 gigawatt-hours of pumped hydro alongside modest extra annual renewables, while the current pipeline of roughly 192 gigawatt-hours leaves a significant delivery gap. The paper therefore sets a clear policy task: update planning tools and align procurement, permitting and finance to enable the larger build the corrected models imply.

What to watch

• Watch for citations of the Cell Reports Physical Science paper by Australian planners and advisory bodies; no date has been set.
• Watch for any public responses from the Australian National University team or government energy departments to the study’s call for updated pumped-hydro assumptions; no date has been set.