The share of solar and wind powering Australia's main grid has reached a new high while coal power's contribution dipped below 50 per cent for the first time.
Renewable energy supplied a record 46 per cent of the national energy market's electricity in the three months to December, driving emissions to record low levels.
The Australian Energy Market Operator's (AEMO) report shows coal's dominance in the grid is slipping as power plants become less reliable and continue to close, and more solar and wind comes online.
Investors were installing renewables because solar and wind were the lowest-cost forms of new generation, said Johanna Bowyer, lead analyst for Australian electricity at the Institute for Energy Economics and Financial Analysis.
"It was really interesting to see such high renewables levels," she told AAP.
"It's generally not that well understood by people that renewables actually do provide such a large proportion of the energy supply in the national electricity market."
Despite record contributions from clean energy, power prices were still higher compared with the same time last year.
The market operator chalked this up to coal plant outages leading to greater reliance on gas - the most expensive form of generation - as well as warmer-than-usual weather prompting households to fire up their air conditioners and fans and push up power demand.
Transmission constraints also played a role, hampering the sharing of low-cost renewable energy across the grid, said AEMO executive general manager of reform delivery Violette Mouchaileh.
"Recent operating conditions highlight the role new transmission projects under way - such as VNI West, Project EnergyConnect and HumeLink - will play in sharing the lowest-cost energy throughout the NEM (National Electricity Market)," Ms Mouchaileh said.
Ms Bowyer said southern states of South Australia, Victoria and Tasmania were better able to share low-cost renewables around while transmission lines to NSW and Queensland experienced constraints.
Wholesale prices in Queensland and NSW were almost double their southern counterparts, reflecting restricted transmission as well as higher demand and the northern states' reliance on black coal stations, which experienced a number of unplanned outages.
Across the entire grid, wholesale electricity prices averaged $88 per megawatt hour in the December quarter, rising 83 per cent from a "very mild" last three months of 2023.
Average prices were still 26 per cent lower than the previous quarter, however.
Ms Bowyer said the market operator was reporting an increasingly extreme "duck curve" - that is, low prices in the middle of the day while solar is generating and high prices in the evening as air-conditioners are fired up to keep cool during warmer nights.
"The duck curve is getting duckier," she said.
Solar generating during the day helped push prices towards zero or into negatives 23.1 per cent of the time, representing a new quarterly record.
"We know that storage will help a lot, because it can soak up that low-cost renewable power in the middle of the day and then release it in the evening, and that will actually smooth out those prices in the evening," she said.
Shifting demand to the middle of the day would also help prevent peaky evening prices, she added.
Energy Minister Chris Bowen said Thursday's update confirmed the energy system was evolving as expected.
"The data confirms what we know - unreliable coal is having a negative impact on energy prices, more renewables in the system bring wholesale prices down, and new transmission infrastructure is critical to keeping prices lower," he said.
"We are building an energy grid so everyone, everywhere has access to the cheapest form of energy at any given time."
Australia's 18 remaining coal-fired power stations in the national electricity market were fast approaching their use-by date, Clean Energy Council national spokesperson Chris O'Keefe said, while driving up energy prices.
"The economics and the engineering don't lie - renewables, firmed by more storage such as batteries and pumped hydro, gas, as well as upgraded transmission, are the only feasible pathway towards building a cleaner, lower cost energy system for all Australians, sooner."
