This is going to be another one of those article response posts, but this time I’ll be brief.
What did you read this time? In an ABC article Watchdog circles WA utility as ‘unusual’ battery charging pushes prices higher they share a plot showing us how the grid-scale batteries in WA have flattened the electricity prices between Q4 2024 and Q4 2025. This is pretty straightforward and a good example of one of the primary benefits of the load shifting batteries enable, and is clearly communicated in the plot below.
A little explanation, please? Those who have looked at a time of use (ToU) energy plan might see some correlation between the 2024 daily average price (and to a lesser degree the 2025 data) and the pricing offered to you by your retailer. If you want more, I go into a lot more detail in my previous post, Time of Use Energy Plans, otherwise below is my very brief visual explainer for daily electricity pricing in Australia.
ToU pricing and electricity demand in Australia
A time-of-use tariff against the shape of a typical demand day
Hover to show time of day and click a series in legend to show/hide.
Show source data
| Tariff | Time of Day | Cost (AUD) |
|---|---|---|
| Daily Charge | 1.133 / day | |
| Solar Soak | 11:00 – 16:00 | 0.1815 / kWh |
| Offpeak | 21:00 – 11:00 | 0.22330 / kWh |
| Peak | 16:00 – 21:00 | 0.40700 / kWh |
Usage and daily supply rates include GST. Rates shown are before any conditional discount.
Indicative demand is not measured system demand. It is the shape of the WA wholesale spot price for Q4 2024, the year before grid-scale batteries flattened it (see the companion cost-comparison chart), normalised to its own range: 0% at the day’s lowest half-hourly average, 100% at its highest. Wholesale price and demand are not the same thing — price also reflects supply-side conditions such as rooftop solar output and generator bidding, which is why the market can go negative at midday even though demand never does — but under merit-order dispatch the two track closely enough for the shape of this curve to stand in for a typical demand day.
Sources. Wholesale prices: ABC News, Batteries flatten average daily energy
prices, Datawrapper chart fH1Uf, 20 August 2026, from AEMO
Quarterly Energy Dynamics — Q4 2025; dataset retrieved from
datawrapper.dwcdn.net/fH1Uf/2/dataset.csv on 2 September 2026, which carries
48 dated intervals plus 44 duplicate rows in an older label format that are excluded.
Rates: GloBird Energy Boost from 1 August 2026, at
crossgeared.com/time-of-use-energy-plans.
And, this is relevant how? Finally, here's a direct comparison with my (very limited) before and after late winter battery forced loading showing my ToU cost per kWh compared to my effective cost per kWh making some assumptions about losses and system efficiency using actual data. However, these data are so limited that it probably better described as an anecdote. Also note that the scales for these plots are completely different as my costs are retail in cents per kWh and the WA wholesale spot price is in AUD per MWh (1 AUD = 100 cents and 1MWh = 1,000kWh).
What Batteries Have Done in WA and What They're Doing for Me
Grid batteries flattened a wholesale price curve; one home battery halved a peak tariff
Hover either panel to read the same clock hour in both, or click a series to hide it. Arrow keys step through the day.
WA Wholesale Spot Price
Average half-hourly price, Q4 2024 against Q4 2025.
ToU Tariff and Effective Cost
Battery forced loading, 7–23 August 2026.
Show source data
| Series | Mean | Minimum | Maximum | Peak-to-trough |
|---|---|---|---|---|
| Q4 2024 | 79.93 | −67.30 at 12:00 | 203.14 at 18:00 | 270.44 |
| Q4 2025 | 69.55 | 28.40 at 13:30 | 121.49 at 18:00 | 93.09 |
| Tariff | Time of Day | Cost (AUD) |
|---|---|---|
| Daily Charge | 1.133 / day | |
| Solar Soak | 11:00 – 16:00 | 0.1815 / kWh |
| Offpeak | 21:00 – 11:00 | 0.22330 / kWh |
| Peak | 16:00 – 21:00 | 0.40700 / kWh |
Ten of the 48 wholesale intervals were negative in Q4 2024; none were in Q4 2025. Usage and daily supply rates include GST. Rates shown are before any conditional discount.
My usage data: [add one paragraph description of source data from GloBird]
Effective cost is measured rather than modelled. For each half hour, coverage is the share of the 17 days from 7 to 23 August 2026 on which no meaningful grid import occurred, taking anything above 0.05 kWh in a half hour as the battery no longer carrying the house, against standby readings near 0.006 kWh. Energy the battery supplies was bought earlier at the solar soak rate, so it costs that divided by round-trip efficiency: 20.625c at 88%, ranging from 20.167c at 90% to 21.353c at 85%, which is the shaded band. Effective cost is coverage times storage cost plus the remainder at the published rate. Between 08:00 and 16:00 the published rate stands, because an absence of import there means solar or the forced load itself rather than the battery discharging. Round-trip efficiency is estimated, not measured.
The two panels are scaled so the Q4 2025 mean and the effective mean sit at the same height. That alignment is what makes the shapes comparable; the heights themselves are not, since one is a wholesale price in dollars per megawatt-hour and the other a retail rate in cents per kilowatt-hour. The shared cursor reads the same clock hour in each panel, not the same instant, since the two regions keep different time.
Sources. Wholesale prices: ABC News, Batteries flatten average daily energy prices,
Datawrapper chart fH1Uf, 20 August 2026, from AEMO Quarterly Energy Dynamics
— Q4 2025; dataset retrieved from
datawrapper.dwcdn.net/fH1Uf/2/dataset.csv on 2 September 2026, which carries 48
dated intervals plus 44 duplicate rows in an older label format that are excluded.
Accompanied Daniel
Mercer, “Watchdog circles WA utility as ‘unusual’ battery charging pushes
prices higher”, ABC News, 2 September 2026. Household data: half-hourly interval
metering, NMI 60010826437, meter 0007644, streams E1 consumption and B1 solar export,
supplied by GloBird Energy, 23 January to 2 September 2026, timestamps AEST. Rates: GloBird
Energy Boost from 1 August 2026, at
crossgeared.com/time-of-use-energy-plans.
Hardware: Fronius Primo GEN24 5.0 Plus with a 19.3kWh BYD HVM battery, forced loading at a
minimum of 2kW between 11:00 and 16:00, at
crossgeared.com/battery-management.
What does this tell us? Much like the batteries in WA, my home battery is flattening the daily cost of electricity to the point where peak pricing has essentially been completely offset with lower-priced electricity from the solar soak period. I can see two equally true interpretations of these data.
A properly managed solar and home battery system can eliminate peak pricing, even in the winter!
- Your local solar installer
Home battery offers no benefit for nineteen hours every day.
- Large news source that controls half the newspapers
Whichever way you look at it, the automated management I've set up for my particular home and solar/battery system means we can be more flexible when we use electricity with less consideration given to the prices set by our retailer. Meaning we can run the heat, oven, dishwasher, or whatever* whenever needed. Furthermore, we can use electricity in the evening peak without contributing to overall demand and contribute just a little to reduce the demand for fossil fuelled energy.
*- Big caveat here, maybe not charging the EVs as they have a battery capacity 2-3 times lager than the home battery.
References and resources
- Watchdog circles WA utility as 'unusual' battery charging pushes prices higher (https://www.abc.net.au/news/2026-09-02/wa-energy-watchdog-probes-battery-charging-price-rise/107104282)
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