New generation, transmission lines and energy storage are needed to keep the lights on in homes and businesses as ageing coal power plants shut down.
In a national electricity market update released on Tuesday, the Australian Energy Market Operator warns the reliability of the electricity grid is in doubt over the next 10 years without new investments - including gas.
AEMO CEO Daniel Westerman said timely investment in the grid is needed as Australia ends its traditional dependency on coal-fired generation and faces delays on some major projects.
Previously forecast short-term reliability gaps in South Australia (2023/24) and Victoria (2024/25) have been filled by new gas, wind and battery developments, along with a delay to the retirement of a gas generator, the report found.
But mainland states in the national electricity market are forecast to breach the reliability standard from 2027 onwards, with at least five coal-fired power stations - totalling 13 per cent of the market's capacity - expected to retire.
Projects that could reduce the reliability gap include Transgrid's 360km HumeLink to connect Wagga Wagga, Bannaby and Maragle and increase the amount of renewable energy that can be sent across NSW.
The Hunter Transmission Project, Marinus Link, other transmission projects, battery developments in various states, and Victoria's offshore wind plans may also reduce the forecast reliability risk, according to the report.
Since the last report released in August, Australia's largest generator AGL Energy has brought forward the closure of the 800-megawatt gas-fired Torrens Island B plant in South Australia from 2035 to 2026.
Snowy Hydro has advised a one-year delay to December 2024 on the controversial $1.3 billion gas-fired Kurri Kurri power station and a delay from December 2026 to December 2027 on the Snowy 2.0 hydro project.
The Waratah Super Battery Project in NSW is on track for late 2025, coinciding with the closure of Origin's Eraring coal-fired power station - Australia's largest coal plant and the source of a quarter of NSW's power output.
Origin Energy has reported a three-year extension for the 180MW gas-fired Osborne plant in South Australia to 2026, ditching plans to close in December.
South Australia's 123MW Bolivar power station, a so-called "peaker" plant powered by gas and diesel when there's high demand, has come online.
New generation since the 2022 statement includes 461MW of battery energy storage systems and 1326MW of wind developments.
Proposed generation and storage projects would triple existing generation capacity, with large-scale solar, wind and batteries accounting for 86 per cent.
"Investment in firming generation, such as pumped hydro, gas and long-duration batteries, is critical to complement our growing fleet of weather-dependent renewable generation," Mr Westerman said.
