This is the continuation of the previous post. https://crudeoilpeak.info/premier-nsw-energy-guzzler-in-winter-coal-plants-running-at-90-capacity-during-critical-evening-periods
Fig 1: Another cold and rainy winter day
We are supposed to electrify with renewables and energy storage. https://smartlifestyleaustralia.com.au/electrification-australias-path-to-lower-carbon-emissions
But in NSW, that’s not happening at the speed required, at least not in winter.
| Name of coal fired power plant | Units in MW |
Available capacity in MW |
Generation midnight in MW 12 Aug 2025 |
% of available capacity |
| Bayswater | 4 x 660 | 2,640 | 2,711 | 102.7% |
| Eraring | 3 x 720 | 2,160 | 2,006 | 92.9% |
| Mt Piper | 700 + 730 | 1,430 | 1,404 | 98.2% |
| Vales Point | 2 x 660 | 1,320 | 1,218 | 92.3% |
| Total | 7,550 | 7,339 | 97% |
1 unit of Eraring is offline since Aug 5th. This means that the available coal plant capacity is only 7,550 MW
Fig 2: Coal fired power 7,300 MW (97% of available capacity) for 15 long hrs all through the night
(Except a 500 MW dip around 4 am)
Let’s go through the plants one by one:
Fig 3: Bayswater 15 hrs slightly above registered capacity
Fig 4: Eraring with 3 units for 16.5 hrs at 2,000 MW
On 13th August, generation was as follows: ER02: 14.612 MWh, ER03: 15,834 MWh and ER04: 15,057 MWh
Fig 5: Mt Piper for 13 hrs close to capacity with a night-time drop
Fig 6: Vales Point for 16 hrs at 90% of capacity
Fig 7: There were no price spikes higher than $300/MWh
Now let’s look at the role of batteries and renewable energies as this is a hot topic.
3 ways batteries are energising Australia: Our cars, homes and energy grid
https://www.climatecouncil.org.au/resources/battery-storage-batteries-decarbonising-australia-cars-homes-grid-2
Fig 8: NSW batteries in operation July/August 421 MW/645 MWh
Progress of Eraring battery: https://www.originenergy.com.au/about/who-we-are/what-we-do/generation/eraring-projects/battery
Fig 9: NSW batteries charging and discharging: Screenshot of NEM website
Charging is negative (load on the grid, light blue) and discharging into the grid is positive (dark blue). In this graph, discharging obscures charging which is a bit confusing if one is accustomed to how Excel is stacking positive and negative numbers (shown in the next graph)
Fig 10: NSW batteries charging (below horizontal axis) and discharging (above axis)
The average charging per day was 1.1 GWh/day, the average discharging 0.85 GWh/day.
The state of charching (SoC) at the beginning of the period is unknown. There is more charging than discharging (34.2-25.6 = 8.6 GWh). If the storage capacities in Fig 8 are correct the maximum at the end of the period could be 0.645 GWh (excluding Waratah). This means the efficiency of converting charged energy into discharged energy for the grid is at best 25.6/(34.2 – 0.645)= 76%. The losses occur in inverters, transformers, auxiliary power supplies, self-discharge (3-5% per day for hold-back reserve – contingencies) and other services like frequency control, much of which is not deducted from the gross discharge data.
So the average daily discharge is 0.85 x 0.76 = 0.65 GWh/day
Now let’s compare how much of solar energy was stored:
Fig 11: NSW battery charging from solar utility 8-14 Aug 2025 (area below zero)
The charging from solar power is shown in those small yellow areas below the axis. Compared to the available solar energy this is small, around 4%. Note also that on several days charging happened at night, apparently preparing for the morning peak. So the percentage of solar energy stored is less than 4%.
Battery by battery
Fig 12: Broken Hill battery
Fig 13: Capital battery
Fig 14: Darlington Point battery
Fig 15: Riverina 1 battery
Fig 16: Riverina 2 battery
Fig 17: Waratah battery in testing mode
Most batteries show 2 charging/discharging cycles per day in 5 of 7 days. As an example, here is the summary of all batteries in NSW on 12/13th August:
Fig 18: Two charging/discharging cycles on 12th August 2025
Let’s see whether the charging at night came from wind:
Fig 19: NSW battery charging from wind 8-14 Aug 2025 (area below zero)
Fig 19 with wind is similar to Fig 8 with solar. We see that the areas under the axis (charging) at night (grey areas) are indeed green, ie. could be argued to come from wind. But nothing can stop battery operators to charge at night if there is no wind, meaning the primary power would come from coal.
Summary:
The current set of batteries in operation have short, daily and even half-daily charge/discharge cycles to function as peaking plants. The average daily discharge of 0.65 GWh is small compared to the generation of just 1 Eraring unit of 14 GWh/day. Battery capacity would need to be ramped up considerably to make any contribution to replace a coal plant running continuously. The next batteries Eraring and Waratah to come online are big and will bring some improvement. And there are many committed projects. So the above calculations have to be updated regularly, also depending on the season. The bottom line, however, is that that system must work at all times, also on windless winter days/nights like on the 13th of August 2025.
The next post in this series will be on hydro, gas and imports.
Addendum
Eraring coal fired power plant extension of time
In this very month Eraring was supposed to shut down. But a year ago the NSW government extended its life by 2 years until August 2027
NSW Government secures two-year extension to Eraring Power Station to manage reliability and price risks
23 May 2024
https://www.nsw.gov.au/media-releases/nsw-government-secures-two-year-extension-to-eraring-power-station
Now that 2027 date is also in doubt.
Interview of ABC’s ‘The Business’ (Alicia Berry) with Origin CEO Frank Calabria
14 Aug 2025
Alicia: So when Eraring goes offline in August 2027 will the shortfall from that power station be filled by renewables or gas?
Frank: Oh no. I think the bulk energy that’s coming into the system, when you think about energy as we go through this transition, bulk energy is going to come from renewables but we still have an existing system that has a combination of gas, coal, hydro and renewable energy. And so I think you’ll find it will be a combination that comes in. But clearly we are investing in a very large wind farm [Yanko Delta, 1.5 GW, South West Renewable Energy Zone] to bring that in to replace that Eraring over time. And that will depend on the timing of that windfarm relative to the date we close Eraring. So there could be a period of time in which we are getting energy from a variety of sources. But if you think about the transition more broadly as Eraring comes out of the system that energy will be replaced by renewable energy and that’s why we have to think about the timing because that’s also dependent on energy infrastructure being built.
https://www.abc.net.au/news/programs/the-business/2025-08-14/will-consumers-end-up-paying-for-the-energy/105656026
Origin considers keeping Eraring plant open for longer as profits jump
14 Aug 2025
Origin Energy CEO Calabria said that while Origin’s assumption was that it would still close its only coal plant in August 2027 as planned, the build-out of cleaner generation like wind and solar farms was “not straightforward”, requiring the company to assess a range of scenarios for future supply.
Origin would assess security of supply, affordability and emissions before deciding on a final plan, he said, adding that the company was continuing to invest in the 2880-megawatt power station on the Central Coast.
“We are keeping the plant up to scratch which is important in this market.” Origin chief financial officer Tony Lucas said of the spending on Eraring.
The NSW government reached an agreement with Origin last year to extend the life of Eraring by two years beyond its targeted closure date of August amid concerns about security of supply.
https://www.afr.com/companies/energy/origin-positive-on-outlook-after-26pc-jump-in-full-year-profit-20250808-p5mle5
Australia’s biggest energy retailer hits go slow button on wind and solar, mulling options on Eraring
14 Aug 2025
https://reneweconomy.com.au/australias-biggest-energy-retailer-hits-go-slow-button-on-wind-and-solar-hedges-on-eraring-closure/
Eraring Power Station in the news, again … might stay open (even) longer
15 Aug 2025
https://wattclarity.com.au/articles/2025/08/15aug-eraring-mightstayopen/
