A bold headline summarizes the core issue: big batteries are already shaping South Australia’s power demand, delivering more than a third of total needs before sunrise. But here’s where it gets controversial: the same batteries dip into a negative-price daytime window as rooftop solar floods the grid, creating a complex dance between storage, rooftop PV, and utility-scale renewables.
On Sunday morning, South Australia hit a new early-morning discharge record, supplying 40.6% of state demand at 4:50am. This eclipsed the prior 40% peak that had been set the prior Tuesday evening. The early discharge was quickly followed by a sharp drop in overall demand once rooftop PV surged, turning total demand briefly negative from about 10:45 to 15:15, meaning rooftop PV output exceeded local demand.
During this window, utility-scale solar and wind were largely curtailed because there wasn’t enough demand to absorb them. Even if dispatch were possible, it would likely be at a loss. The batteries then switched from discharging to charging during the negative-price interval, providing needed load, and resumed discharging later in the afternoon as prices recovered and gas-fired generation stepped in to meet demand profitably.
Key observations and takeaways
- Behind-the-meter rooftop PV created a pronounced demand trough, pulling total demand downward.
- Utility solar and wind became the “victims” of the Dolphin Curve of abundance: with little demand to serve and export limits in place, these clean resources faced near-total dispatch suppression and revenue erosion.
- The early discharge wasn’t simply driven by a morning ramp; at 4:50am the demand was steady and the SA price stood at $31/MWh—too low to justify gas-fired generation and not high enough to fully explain aggressive discharge based on price alone.
- The day displayed a broad price range: a high of $232/MWh at 21:55, an average around -$4.45/MWh, and a low of -$323/MWh at 09:35.
- Both arbitrage and minimum-solar-load preparation are plausible explanations: batteries may have been creating headroom for expected negative-price charging, or pre-emptively reducing state of charge ahead of the day’s Minimum System Load Market Notices—though no battery intervention notices were issued.
- Curtailment was extensive: the classic “Dolphin Curve” appears when rooftop PV growth pushes utility solar and wind out of the market during peak solar hours.
Curtailment note: The daylight-hour curtailment of utility solar and wind reflected an extreme surplus from rooftop PV, underscoring how behind-the-meter generation increasingly rewrites operational realities for the National Electricity Market. Gas use remained minimal—roughly 80–90 MW—to support system strength during this period.
South Australia’s operating envelope is tightening: deeper demand troughs driven by rooftop PV, anticipated storage swings enabled by favorable price spreads, and recurring curtailment of utility-scale renewables—all contributing to a cycle of “revenue destruction” when local demand lags behind supply.
This narrative is adapted from a LinkedIn post with the author’s permission.
