NEM Data Spotlight: Combined solar generation falls 21% in June as end-of-month pricing spike pushes AU$120/MWh

Analysis of data sourced from Open Electricity (formerly OpenNEM) shows that the month-on-month contraction is consistent with the seasonal pattern that has defined each winter transition period in the dataset.

In May 2026, combined solar generation had already fallen 21% from April to May, and the June contraction extends that trajectory into the heart of winter. The sequential declines from December 2025’s combined peak of 5,701GWh to June 2026’s 2,413GWh represent a 58% reduction across six months, tracking closely with the equivalent winter trough recorded in June 2025.

The June generation totals for both segments have moved broadly in line with prior-year seasonal norms, suggesting that weather conditions in June 2026 were comparable to those in June 2025 rather than particularly adverse.

Utility-scale solar at 1,092GWh was the lowest monthly total since June 2025’s 1,028GWh, though it remained 6.3% above that prior-year figure, reflecting the continued expansion of large-scale capacity commissioned across the intervening twelve months.

The year-on-year growth rate of 6.3% in June is the weakest recorded in the dataset since the series began, a product both of the solar resource constraints inherent to winter and the fact that the comparable June 2025 figure was itself not particularly depressed.

Rooftop solar at 1,321GWh fell 13.1% year-on-year from June 2025’s 1,446GWh, an unusual reversal of the upward trend that has characterised the segment across every month of the past two years.

The year-on-year decline in rooftop output is likely attributable to a combination of cloud cover and reduced irradiance rather than a structural change in installed capacity, which has continued to grow.

However, the magnitude of the decline warrants attention: a 13% rooftop contraction against a prior-year baseline that was itself a winter low is a more pronounced drop than the seasonal norm would suggest.

Daily generation data for June shows a clear two-phase pattern across the month. The first 10 days produced relatively stable, if declining, output, with utility-scale generation ranging from 29.6GWh to 53GWh as weather conditions varied.

Day six was the strongest of the month at 53GWh for utility-scale and 55GWh for rooftop, consistent with a clear winter day producing near-maximum irradiance for the season. A sustained trough then settled across the middle of the month, with daily utility-scale figures clustering between 25GWh and 43GWh across days 11 to 26 before falling further in the final four days.

The lowest utility-scale daily output was recorded on 29 June at 27.4GWh, and the lowest rooftop figure was recorded on 30 June at 28.8GWh, the final days of the month representing the weakest generation conditions to date.

Pricing spike accelerates through the final week

The pricing data for June reveals a month that ended under materially different market conditions than those prevailing at its opening.

Average daily prices for both utility-scale and rooftop solar were broadly contained below AU$90/MWh (US$62.43/MWh) through the first three weeks of the month, with several days recording averages below AU$50/MWh and a low of AU$11.69/MWh for utility-scale on day three.

That early-month pricing environment reflected an adequate renewable energy supply relative to demand across most of the NEM, consistent with what April 2026 saw, when the transition into autumn conditions saw prices remain relatively contained despite falling generation volumes.

From day 21 onwards, prices began a sustained climb that accelerated sharply through the final week. Day 22 recorded AU$88.51/MWh for utility-scale and AU$104.78/MWh for rooftop, the first day in the month on which rooftop pricing crossed the AU$100/MWh threshold.

From day 24 onwards, average daily prices remained consistently above AU$100/MWh for both segments, with day 30 recording the month’s peak at AU$118.27/MWh for utility-scale and AU$120.78/MWh for rooftop.

In the final week, rooftop solar commanded a premium over utility-scale generation on several days, including an AU$16.74/MWh spread on day 22, reflecting the distributed nature of rooftop generation and its role in offsetting localised demand peaks during periods of grid stress.

The pricing pattern reflects the low-wind period that affected South Australia toward the end of June, which drove spot prices higher across the NEM as dispatchable capacity was called upon to compensate for reduced renewable energy output.

South Australia’s spot price for the month averaged above AU$125/MWh, materially above the sub-AU$90/MWh averages recorded in other NEM states. The end-of-month price spike is less severe than the event that defined May 2026, when a mid-month generation shortfall pushed the NEM average to AU$225.88/MWh on 18 May.

June’s pricing spike was both later in the month and lower in absolute terms, though the sustained run of days above AU$100/MWh through the final week represents a more prolonged period of elevated prices than May’s sharper single-day event.

As previously noted by PV Tech, the NEM’s pricing behaviour has been characterised by episodes of volatility at both extremes across 2026, with summer negative pricing giving way to winter scarcity events as the renewable energy generation mix shifts with the seasons.

Negative pricing, which featured across both segments in February 2026 during the summer peak, was absent from the June dataset entirely, consistent with the pattern observed in April and May, when solar generation volumes dropped below the threshold at which midday surpluses routinely push prices below zero.

The absence of negative prices in June is consistent with winter demand patterns, where heating load sustains consumption through the middle of the day, preventing the excess generation conditions that characterise summer and spring afternoons.

You can explore previous solar generation performance in our NEM Data Spotlight series, with all entries available to PV Tech Premium subscribers.