“Miles lower:” Rooftop PV takes biggest bite yet out of grid demand in Australia’s biggest coal state

Electricity demand in NSW – the state with the biggest fleet of coal generators – took a surprising and big fall on Sunday after rooftop solar grabbed a record 60 per cent share of electricity demand.

According to several sources – GPG NEMWatch and Watt Clarity – the level of market and operating demand fell well below their previous lows, and surprisingly so because such records usually fall in spring, not in late summer.

“This is miles lower than the previous low point,” Watt Clarity’s Paul McArdle observed in a post. According to his data, NSW “market demand” fell to a low of 2532 MW, some 484 MW beneath the previous low set in October last year.

His observations were echoed by the data sets at NEMLog, which describes “market demand” as “network demand”, and also observed a similar plunge in “operational demand” at the same time.

All of this occurred as the share of rooftop solar PV reached 60 per cent for the first time in NSW, which is also the biggest grid in the country in terms of both demand and capacity. This was up from 58.9 per cent in October last year, in the middle of spring when such records usually occur.

McArdle suggested that despite the strong solar conditions, the relatively low temperatures meant that the use of air conditioners may have fallen considerably, contributing to the low demand levels, which would already have been subdued due to the weekend.

The demand low had an impact on coal fired power stations and the amount of capacity able to run at the time, but it also had an impact on large scale renewables, with curtailment levels also hitting a new high, particularly in terms of market share.

GPE NEMLog’s Geoff Eldridge says Sunday witnessed multiple new curtailment records across the grid, with solar curtailment hitting a new peak in NSW of 3,101 MW, up 401 MW from the previous peak in December last year, and a new peak of 5,897 MW across the whole grid, up 461 MW than the previous record set in earlier October.

“For the first time, NSW total demand share of native demand dropped below 30%, further highlighting the shift towards behind-the-meter generation,” Eldridge noted in a post on LinkedIn.

“With strong utility solar availability across NSW and the (south east of the National Electricity Market), curtailment increased as prices dropped below LGC levels, allowing 11 of 12 NSW coal units (Eraring 4 came out-of-service early on Sat) to remain in service at minimum loads across the day.

“These records highlight the increasing challenges of integrating high solar output into the grid. Managing curtailment and ensuring grid flexibility through interconnection, storage, and market reforms will be key to maintaining stability.”