On January 27, 2026, South Australia endured a brutal heatwave — including the hottest night on record for Adelaide — and the electricity grid felt the heat too. What unfolded offers a sobering snapshot of a system already flirting with its limits: when demand peaks and renewable contributions wane, traditional power sources still hold all the cards.
South Australia has been celebrated internationally for its high renewable share, clocking nearly 75 per cent wind and solar penetration over the past year and targeting "net 100 per cent renewables" by the end of next year. That's remarkable — but there's a catch hiding behind the headlines.
Batteries Fizzle When They're Most Needed
The state's expanding fleet of big batteries — once hailed as a grid-saving technology — nearly ran out of stored energy by about 8:30 pm on that taxing night. With only about 1.5 hours of storage capacity on average, these batteries could not sustain evening demand. Once depleted, the grid handed the reins back to peaking gas plants and diesel generators, which promptly cashed in on sky-high wholesale prices.
Here's the brutal logic on display:
Batteries discharge when the sun goes down or wind dies — roughly what they are designed for.
But their duration is short — measured in hours, not days or even entire evenings.
When stretched beyond that, they simply become useless until they recharge.
In practice, this means renewables plus batteries can only supply part of the energy transition puzzle.
When demand stays elevated — as it did during the heatwave — fossil fuel plants still set prices and fill the gap. The wholesale price spiked near the market cap of more than $20,000 per megawatt-hour as gas and diesel operators responded to relentless demand pressured by stifling heat.
The "Dependency Paradox" of Renewables
This episode highlights a core fragility of a renewable-centric grid:
1.Intermittency is inherent
Renewables only generate when the wind blows or sun shines. That's not a bug — it's a fundamental physical truth.
2.Current storage is limited
Utility-scale batteries are large, but measured in megawatt-hours, not the terawatt-hours needed to smooth extended demand troughs or multi-day weather events.
3.Extreme conditions still reveal the gaps
During heatwaves, evening peak demand doesn't coincide with solar output. Wind patterns may be weak. Batteries peak early, then fade. That's precisely when fossil generators are still indispensable.
This isn't speculative fear-mongering; it's basic grid physics paired with real world data.
Day and night are different beasts — and it's that very transition that continues to expose the system's Achilles' heel.
The Inescapable Conclusion
High renewable penetration is possible under favourable conditions.
But system stability and continuity still rely on dispatchable power sources when renewables can't deliver on demand.
Batteries today are useful buffers, not full replacements for peak capacity.
Anyone who promises that wind, solar and short-duration batteries alone can guarantee 24/7 reliability is overpromising — and potentially underestimating the very real costs when the chips are down.