Rooftop solar supplies 99.9% of South Australia’s electricity demand

At 1.30pm on 31 August, South Australian rooftops were meeting 99.9% of the state’s total electricity demand. The Australian Energy Market Operator, or AEMO, said demand from grid-scale generation fell to just 2 MW, a new winter record.

Mild temperatures and clear skies across southeastern Australia helped push demand down. High rooftop output and negative wholesale prices coincided with batteries charging at above-average rates, absorbing excess renewable electricity for use during the evening peak.

The record was part of a wider shift. In the National Electricity Market (NEM), the country’s broader electricity market, minimum operational demand reached 11,992 MW at 1.30pm, below the previous winter low of 12,144 MW set in August 2024. At that point, rooftop solar contributed close to 54% of underlying demand, while renewables including rooftop solar, grid-scale solar and wind accounted for 71% of generation. Battery charging accounted for about 10.5% of total generation, and just over 2% was used for hydro pumping.

The numbers rest on a substantial rooftop fleet. Australia leads the world in rooftop solar penetration, with 41% of residential, commercial and industrial premises hosting systems with a combined 28.3 GW of generation capacity. South Australia has solar arrays on 57% of its rooftops, equivalent to 2.92 GW of generation capacity.

Concretely, this means South Australia’s daytime electricity demand can, at a particular moment, be met almost entirely by rooftop systems, while batteries absorb some surplus for the evening peak. It does not mean rooftop solar supplies the state continuously: the record describes one 1.30pm period under mild, clear conditions. AEMO says the system is increasingly balancing high renewable generation in real time with batteries, hydro, gas and transmission, making flexibility, storage and operational capability central to keeping supply secure and reliable.