Grid batteries set the NEM spot price in 48% of September-quarter intervals, wholesale power averaged $63, and they beat gas in the evening peak
On 23 October 2026 AEMO released its September-quarter report. Grid batteries set the National Electricity Market spot price in 48% of dispatch intervals, up from 18% a year earlier. Wholesale power averaged $63/MWh, down 27% on the year. In the evening peak, batteries supplied 8.0% of generation and gas 5.1%. These are grid batteries. A fixed retail invoice is a different piece of paper.
A factory buying power on a wholesale-linked contract met this price in the September quarter. A factory on a fixed retail rate did not see $63 on the invoice. The Australian Energy Market Operator says the wholesale average contributes to retail prices. Contribution is not the bill.
The quarter is 1 July to 30 September 2026. AEMO published the report on 23 October 2026. Violette Mouchaileh, AEMO's executive general manager for policy and corporate affairs, said batteries "continue to shift record amounts of renewable energy into the higher-demand evening period, when households and businesses typically need more power."
Grid batteries set the spot price in 48% of dispatch intervals. A year earlier the share was 18%. Charging set the price in 24% of intervals. Discharging set it in 24%. The report says charging rose 15 percentage points and discharge rose 14. 24 plus 24 is 48, by our arithmetic, and that matches the combined figure. The June-quarter note covered the previous report: 36% of intervals, and a $107 average in the intervals where discharge set the price. This 48% is the next quarter. The $98 below is a different average.
The clock. In the evening peak, battery discharge set the price in 60% of intervals, up 34 percentage points. In daylight, 10:00 to 16:00, battery charging set the price in 49% of intervals, up 30 percentage points. On generation, the same report's evening peak, 4pm to 9pm, puts batteries at 8.0% and gas at 5.1%. The report says that is the first quarter batteries supplied more of that peak than gas.
Volume, on an average day. Batteries charged 13.4 gigawatt-hours in the daylight window, 10:00 to 16:00, and discharged 10.9 gigawatt-hours in the evening peak, 4pm to 9pm. A year earlier those figures were 3.7 and 3.2. The 23 October release says gas-fired generation for the quarter fell 34%, to the lowest September-quarter average since 2000.
The wholesale average was $63 a megawatt-hour. That is down $23, or 27%, on the year, and down $11, or 15%, on the June quarter. The report calls it the lowest September-quarter average since 2021. Inside the quarter the average stepped down: $77 in July, $65 in August, $47 in September. A quote that uses $63 for every month of the quarter is using the average, not September.
By region, in the release. Victoria and Tasmania averaged $56 a megawatt-hour. Victoria was down 27%. Tasmania was down 38%. Queensland averaged $61, down 15%. South Australia averaged $69, down 34%. New South Wales averaged $74, down 17%.
Who set the price, by state, in the report. Queensland: battery discharge in 26% of intervals, charging in 28%. New South Wales: 27% and 29%, in that discharge-then-charge order. Victoria, charge and discharge together: 46% of intervals. South Australia, together: 44%. The report does not split Victoria or South Australia into charge and discharge.
What the batteries earned. The volume-weighted average for grid-scale battery discharge was $98 a megawatt-hour, down $70. Charging incurred $32, against $34 a year earlier. Volume-weighted means hours with more energy pull the average. The report says lower evening peak prices cut returns for flexible plant. It does not print the $98 as an evening-only price. The June note's $107 was the average spot price in the intervals where discharge set the price. This $98 is the volume-weighted price of discharge across the quarter.
Homes, so a business does not borrow the figure. Sample data in the report suggests households with rooftop solar and a battery drew around three quarters less power from the grid in the evening peak than households with rooftop solar alone. The summary line does not print how many households are in the sample. It is not a factory meter.
Demand. Underlying demand averaged 25,471 megawatts, up 1.3% on the year, a record for a September quarter. The release says Victoria accounted for almost all of that growth, from electrification, higher industrial demand, and data centres. The release says data centre consumption rose 65% to an average of 225 megawatts. The report prints 136 megawatts in the September quarter of 2025 and 225 megawatts this quarter. A data centre meter is not a warehouse invoice.
Western Australia is a different market. The release says the average real-time electricity price rose 19% to $120.72 a megawatt-hour, the highest quarterly average recorded in the Wholesale Electricity Market. Battery charging doubled. Discharging rose 98%. A site in Perth is not settling at the National Electricity Market's $63.
One certificate line, so it is not read as the roof discount. The report says large-scale generation certificates averaged $7 a certificate, down from $13 in the September quarter of 2025. That paper sits on large solar stations. A separate note covers the small-scale certificate on a workplace roof. The two papers are not the same price.
Analogy: the spot market is a produce auction. This quarter the battery stall cleared 48% of the lots. The average price of the whole auction was $63 a megawatt-hour. The stall's own sales, weighted by how much it sold, earned $98. The docket on a factory door is a different auction.
Good: A public report date, a 48% price-setting share with the charge and discharge split, a $63 wholesale average with the month path, an 8.0% to 5.1% evening comparison, and a volume-weighted discharge price labelled as such.
Bad: No factory tariff. No sample size on the household line. The $98 and the June note's $107 answer different questions. Western Australia's $120.72 is not the eastern average. A fixed retail contract does not reprint $63.
Ugly: Pasting the June quarter's $107 onto this quarter. Reading 48% as the battery on a factory wall. Treating $63 as September, when September averaged $47. Treating a large-scale certificate at $7 as the discount on a small roof. Treating a Perth site as if it bought at the eastern $63.
Soft next step: if a quote leans on the evening wholesale price, read whether the battery is the grid pack in this report or the box on the site. A short consult at Sovryn Energy /consult if you want that line read against the contract.
Source: AEMO, Quarterly Energy Dynamics Q3 2026. Primary for 1 July to 30 September 2026, batteries setting the spot price in 48% of dispatch intervals versus 18% in Q3 2025, charge and discharge each at 24% (charging +15 percentage points, discharge +14), evening-peak discharge price-setting at 60% (+34 percentage points), daylight (1000 hrs to 1600 hrs) charging price-setting at 49% (+30 percentage points), evening peak (1600 hrs to 2100 hrs) generation share 8.0% batteries and 5.1% gas, the first quarter with batteries ahead of gas in that window, average daily charge 13.4 GWh in daylight and discharge 10.9 GWh in the evening peak versus 3.7 GWh and 3.2 GWh in Q3 2025, NEM wholesale average $63/MWh (down $23/MWh, or 27%, on Q3 2025, and down $11/MWh, or 15%, on Q2 2026), the lowest Q3 average since 2021, monthly averages $77/MWh in July, $65/MWh in August and $47/MWh in September, Queensland discharge 26% and charge 28%, New South Wales 27% and 29%, Victoria combined 46%, South Australia combined 44%, battery-discharge volume-weighted average $98/MWh (down $70/MWh) and battery-charge volume-weighted average $32/MWh (from $34/MWh), the line that lower evening peak prices reduced returns for flexible generation, household sample data showing around three quarters less evening-peak grid draw for solar-plus-battery homes than solar-only homes with no sample size in that summary line, underlying demand 25,471 MW, Victoria data centre demand 136 MW in Q3 2025 and 225 MW in Q3 2026, and large-scale generation certificates averaging $7 from $13. 24 plus 24 equals 48 is our arithmetic. The report does not print the $98 as an evening-only price, and it does not split Victoria or South Australia into charge and discharge. AEMO media release, 23 Oct 2026. Primary for the 23 October date, the $63/MWh average and the 27% and 15% falls, regional wholesale prices (Victoria and Tasmania $56/MWh, Victoria -27% and Tasmania -38%, Queensland $61/MWh -15%, South Australia $69/MWh -34%, New South Wales $74/MWh -17%), gas-fired generation down 34% to the lowest Q3 average since 2000, underlying demand up 1.3% to 25,471 MW with Victoria accounting for almost all the growth, data centre consumption up 65% to an average of 225 MW, Violette Mouchaileh's line on batteries shifting renewable energy into the evening when households and businesses typically need more power, her line that batteries set prices in almost half of intervals, up from 18%, the Western Australian real-time average of $120.72/MWh, up 19%, the highest quarterly average recorded in the Wholesale Electricity Market, and battery charging doubling with discharging up 98% in that market. The release says wholesale prices contribute to retail prices. It does not print a factory tariff.