This “curtailment” is carried out to maintain grid stability by preventing an oversupply of electricity at a time when there is simply not enough demand for it.
Analysis of NEM data suggests that annual forced curtailment for 2023-24 was around 4,000 gigawatt-hours (GWh). This represents around 9.3% of Australia’s total annual wind and utility solar generation.
A possible source of flexible demand for this generation is residential off-peak hot water. Off-peak systems account for around 30% of Australian household hot water systems. They are designed to use power overnight, a period when electricity demand has historically been lowest, but during which coal-fired generators have kept producing electricity regardless.
Today, off-peak times could be redefined, and off-peak systems reorganised to consume renewable electricity during the middle of the day, when there is an abundant supply of renewable electricity. Research by the Institute for Sustainable Futures at the University of Technology Sydney estimates that switching off-peak hot water to the middle of the day could have provided around 4,000 GWh of flexible demand in 2020—coincidentally, almost the exact level of renewable curtailment in 2023–24.