When temperatures soared near 40 degrees in Australia’s south-east in February, and violent storms toppled transmission lines in Victoria, utilities like AGL and Origin scrambled to stabilise the power grid.

Thousands of Victorians suffered power outages, and volatility on the state’s futures market surged. As traders covered their shorts it proved a great selling opportunity: high demand for the state’s power sent the average peak spot price north of $2200 per megawatt hour from about $108 a day earlier, tumbling into negative territory a day later.