Rooftop solar reaches stunning new record of 112.9 per cent of state demand

The growth of rooftop solar PV continues to have a massive impact on the grid, and nowhere more so than in South Australia where, on Saturday, it reached a stunning new record of 112.9 per cent of state demand.

The new record was reached, according to data provider GPE NEMLog, at 1.15pm (AEST) on Saturday, and easily beat the previous record of 101.8 per cent that was set on New Year’s Eve in 2023.

The new peak for rooftop solar caused other records to fall – most notably operational demand (minus 205 MW), market demand (231 MW), and network demand (194 MW).

Rooftop solar was able to reach such levels – and push the various demand managements into negative territory – because the state was able to export nearly 400 MW of surplus power to Victoria.

However, it also occurred because some significant load was lost because of storms that tore down 30 towers and two transmissions lines linking BHP’s giant Olympic Dam mine with the state grid on Thursday night. That would likely be at least 100 MW of missing load.

Still, at the time of the record, rooftop solar was producing more than 1,700 MW. Large scale solar and wind were providing another 115 MW, while fossil fuels – just two gas units that were told to run by the market operator to provide system strength and other grid services – accounted for just 80 MW.

The growth of rooftop solar and its influence on the grid has been phenomenal, growing from a maximum share of just 32 per cent in 2018. Last week, for the first time, rooftop solar accounted for more than 50 per cent of grid demand for the entire National Electricity Market.

The growing share of rooftop solar is posing some headaches for the market operator. Rather than seeking to ensure there is enough supply – as it often needs to do in evening peaks and in the middle of heatwaves – the influence of rooftop solar means it may also have to create more demand.

This is not completely new. Water heating systems have historically been scheduled overnight to create demand for coal generators to continue operating. Now these coal generator are having to learn to ramp up and down, and even switch off units completely, to make way for rooftop solar.