The Impact of Rooftop Solar on the Electricity Grid

Rooftop solar power continues to disrupt the business case for coal-fired power generation, setting new records for operational demand and reducing the output of black coal. According to data providers, rooftop solar accounted for a record 46.74% of the National Electricity Market at 12.25pm (AEST) on Saturday, generating 11,000 MW. This had a spill-over effect on the grid, reducing operational demand to a new record low of 12,543 MW and leading to significant curtailment of large-scale wind and solar due to inadequate storage capacity.

During this time, more than 1 GW was being supplied by pumped hydro and battery storage, taking advantage of negative wholesale market prices. The rise of rooftop solar is transforming the grid as it shields households and businesses from rising electricity prices. It also presents challenges in managing large-scale generation, particularly coal, and grid stability.

Previously, the main concern was meeting demand spikes on hot summer evenings, but now there is equal concern about maintaining operational control of the grid as rooftop solar reduces demand to critical levels. The market operator has implemented a program to ensure new rooftop capacity, such as in South Australia, can be orchestrated or switched off if necessary. Additionally, federal and state governments are installing neighborhood batteries to store excess solar power during the day.

Rooftop solar has achieved remarkable milestones in South Australia and Western Australia. In South Australia, rooftop solar reached a record 99.2% of state demand and actually exported power back into the transmission network. In Western Australia, it reached a record share of 77%. Both states are implementing inverter settings to manage rooftop solar systems. Furthermore, Western Australia is deploying giant batteries to store excess solar power for the evening peak.

While the impact of low operational demand is significant in the short term, it is anticipated that new industrial demand for zero emissions power, the adoption of household batteries, and the increase in electric vehicles will mitigate these effects over time.

Source: GPE NEMLog2