Australia’s electricity grid will need to grow threefold by 2050, with large-scale wind, solar, and storage expected to expand five times current levels, according to the Australian Energy Market Operator (Aemo). The warning comes in Aemo’s draft Integrated System Plan for the eastern states and the ACT, which outlines the pathway for meeting rising electricity demand and transitioning away from coal.

Aemo predicts electricity consumption will nearly double over the next 25 years as more homes, industries, vehicles, and datacentres switch to electricity. While renewable energy currently provides around 43% of generation annually, Aemo stresses the pace of expansion must accelerate to meet the federal government’s 2030 target of 82% renewables.

The agency estimates that building the necessary infrastructure along the optimal path would cost $128bn in today’s dollars, but warns that delays will push costs higher and risk grid reliability. Transmission needs are now projected at 6,000km, down from 8,000km previously, largely due to Queensland canceling a major pumped hydro project. The transmission expansion, estimated at $9bn, could save consumers $22bn and cut emissions valued at $2bn.

Coal-fired power is set to shrink, with two-thirds of remaining plants likely to close in the next decade, while the rest may stay online until 2049 following government extensions in Queensland. Remaining coal units will need to cycle up and down more frequently as solar dominates daytime generation.

New gas-fired power plants will be added as backup, but are expected to operate only about 7% of the time, mainly during winter evenings when solar output is low.

Aemo CEO Daniel Westerman said a renewable-led system, supported by storage, gas, and upgraded networks, remains the most cost-effective approach. He warned that slower progress will increase costs for consumers and threaten reliability. David McElrea of the Smart Energy Council summed it up: “The more we delay, the more we pay.”