The growth of rooftop solar continues to have a major impact on Australia’s electricity grids, with the Australian Energy Market Operator reporting significant declines in operational demand in the latest quarter.

The market operator also credits solar for having a major impact on the emissions intensity of the main grid.

“The largest decrease (in emissions intensity) occurred at midday due to increased penetration of solar PV,” it said in its latest Quarterly Energy Dynamics report. (See top graph).

AEMO noted that average operational demand reduced by 362MW in the three months to June, compared to the same period a year earlier. The biggest falls were in NSW ( minus 130 MW) and Victoria (minus 111 MW), which it said was driven by additional rooftop solar PV output and mild peak-time temperatures which reduced heating requirements.

“Reduced demand in Queensland (minus 75 MW) and South Australia (minus 22 MW) was a function of continued growth in rooftop PV output over the middle of the day,” it noted in its latest Quarterly Energy Dynamics report.

The increase in rooftop solar, along with the big growth in large scale solar and wind energy, is changing the dynamics of the market, usually pushing down demand in the middle of the day, when traditional coal and gas generators expected to make pots of money.

AEMO says that overnight generally remains the time with the lowest demand in most of the National Electricity Market, but this is now being challenged by the impact of rooftop solar.

In South Australia, the minimum demand is now almost exclusively in the middle of the day, or late morning. It used to be between 3am and 6am.

A new record low for minimum demand in South Australian was set at 1.30pm on April 27, when operational demand dropped to 749MW. This was 44MW lower than the previous second quarter record last year.

At this time, rooftop PV provided approximately 600MW of output.