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Australia achieved a renewable energy milestone in summer 2025, with solar breaking 30% of total electricity supply for the first time in December and renewables exceeding 50% for three consecutive months. But the breakthrough exposes a critical weakness: solar's extreme seasonal swings mean December's 30% contribution plummets to just 13% in winter, delaying year-round 50% renewable generation until 2029. Despite this, renewables will overtake coal annually by November 2027, with solar now producing 69% of coal's total output, the closest gap in Australia's energy history.
New research reveals solar generation broke through 30% of Australia's total electricity supply in December 2025 for the first time ever, driving renewables to supply more than 50% for a third consecutive month, yet forecasting shows year-round 50% generation won't arrive until 2029 due to solar's extreme seasonal variability.
Analysis of Ember data by Primara Research shows renewables delivered 50.7% of Australia's electricity across Q4 2025, with October, November and December each individually surpassing 50%, the first three months in Australian history to achieve this milestone.
Solar's December performance of 30.5% marks a dramatic surge that now sees solar producing 69% of coal's total output, the closest gap in energy history.
However, the summer success exposes a critical challenge: solar's seasonal variability means replicating 50%+ generation year-round requires significantly more capacity. While coal's lowest monthly output in 2025 was 74% of its highest, solar dropped to just 43%, meaning December's 30% solar contribution was just 13% during June 2025 when daylight hours shrink, sun intensity weakens, and cloud cover increases.
- 30.5% Solar's share of Australia's electricity in December 2025 (first time breaking 30%)
- 50.7% Renewables' share of electricity across Q4 2025 (three consecutive months above 50%)
- 48% to 44% Coals decline of total generation, while wind rose to 14%
- 21.7% Solar's annual share in 2025, up from 19.7% in 2024 (10% year-on-year increase)
- November 2027 When renewables will overtake coal annually
- May 2029 Forecast date for achieving true year-round 50% renewable generation
The forecasting, which analysed production trends across all energy sources, reveals total electricity generation fell marginally despite population growth, pointing to an efficiency dividend from battery storage absorbing excess daytime solar and releasing it during evening peaks.
Australia's renewable energy transition has hit a significant milestone, but also revealed its biggest challenge. While summer now delivers clean energy dominance, solar alone powering nearly a third of the grid in December, the country's progress is hostage to the seasons. Solar's extreme variability (summer output more than double winter's) means achieving consistent year-round renewable generation requires vastly more capacity than summer peaks suggest. For Australians, this has immediate implications: electricity grids must balance dramatic seasonal swings, meaning coal retains a critical backup role until storage and transmission infrastructure catches up. The good news is the trend is clear, renewables will surpass coal annually by late 2027, with year-round 50% generation arriving by 2029. The analysis also suggests efficiency gains from battery storage are helping, with total electricity generation falling despite population growth as batteries absorb excess daytime solar and release it during evening peaks. As coal continues its decline from 48% to 44% in just one year, Australia's energy transformation is accelerating, but the journey from summer success to year-round consistency will define the next three years.
