Timing is everything. The cost of electricity has been a key factor throughout the decarbonisation process. The cost of energy varies (read: increases) over time, but is also variable throughout the day due to time of use (ToU) energy plans. Considering the substantial increase in the overall amount of electricity needed to run all of these electrified systems, timing their use can have a large impact on the utilisation of both solar and stored battery energy, which directly flows on to costs.
Phases. Briefly, I’ve divided this decarbonisation process into three phases: phase 1 was the electrification process, phase 2 was the process of implementing the timing of energy use, and the third phase is the continued adaptation to changing conditions. The timing of these electricity loads in response to ToU energy plans is clearly part of phase 2: timing, as well as phase 3: adaptation. You can read more about the process on my dedicated Home Decarbonisation Project page. I originally visualised this process as layers building upon each other, but the 3-phase pun was irresistible.
First, a little history. In the not-too-distant past, the Australian energy market was very different with state-run utilities, including for electricity generation and distribution. And, along with an initial wave of deregulation across the states and territories beginning in the 1990s, the National Energy Market (NEM) was formed in 1998. The NEM is the wholesale electricity market that allows individual retailers to sell electricity to us. The breadth, degree, and timing of deregulation was highly variable across the states and territories over the couple next decades following deregulation, and I’m not going to get into those details here. But, the important outcome of all of this is that we’re now in 2026 more or less in an environment where individual households and businesses can choose a retailer who themselves can offer rates and plans that compete in a (still highly regulated) market. The primary sources for all of this are deep into government documents and consultants reports, and I suggest Australia’s National Electricity Market after twenty years for a more approachable read.
Like many of you, I enjoy keeping up with the NEM and what’s going on with the market in general, but sometimes have trouble detecting sarcasm in the written form. You can see the NEM in action at explore.openelectricity.org.au. In a recent episode the ABC podcast The Economy, Stupid, The tricks they use to stop us getting cheaper petrol, they buried the lede and discussed a paper Price Discrimination by Negotiation: a Field Experiment in Retail Electricity where Bryne et al. investigate the disparity in pricing for different electricity customers and the methods individuals can use to improve the electricity costs and rates offered by these retailers. They also discuss the advantages of using the compare.energy.vic.gov.au energy comparison tool, which allows individuals to compare actual offers and encourages them to switch plans. On a personal note, I found their insight into the potential effects on different behavioural and sociodemographic groups both revealing and disappointing.
Again, why? On 1 August of this year (2026) I received a notice of a substantial increase in my electricity rates from my current retailer, GloBird. So, as recommended by Bryne et al., I used the compare.energy.vic.gov.au energy comparison tool to find a better offer. GloBird came up (again) as the best offer, and I rang them up to discuss it. After navigating a multi-step phone tree that required selecting some ambiguous options, I arrived at a recording telling me I was the 71st caller in the queue. I tried again the next day with the same process and was assigned caller number 70. I suspect that’s either a coincidence, or these caller queue numbers are pseudo-randomly assigned to discourage you from continuing. Whatever the case, I chose the option to have them call back and they did a few minutes later. The actual real person from the GloBird call centre was helpful, provided the necessary info, had the same pricing from the comparison tool, and gave me an easy path to update my plan.
The ToU energy plan: Now with the new plan scheduled to begin in September, I can reassess my scheduled loads and energy use. In order to do so, I’ve created the data visualisation below (hey, this time I didn’t get distracted and write a new WordPress plugin) that shows all of the relevant ToU plan data along with the context of my load timing and a proxy for solar energy generation. The ToU plan plot shows the GloBird ToU plan pricing throughout the day along with their meagre solar feed-in tariff as well as sunlight and scheduled loads. I suggest you switch the feed-in tariff plot to ‘reality mode’ to see just how close to de minimis this pricing actually is. Said somewhat less pretentiously, “and if you though the 208.9 cents at the petrol station was weird, check out my $0.0010/kWh feed-in tariff“.
Energy Costs and Load Scheduling (2026)
Price, plan, and time of use (ToU) changes
Hover a plan to bring it forward, or click to hide it. Arrow keys step through the day.
Feed-in Tariff
Export rates are the same across all GloBird Boost and GloSave plans. These rates are displayed with a zoomed-in scale as they would otherwise not be detectable to the human eye. Use the zoom feature below to get a more realistic (honest) view of how small they really are.
Scheduled Loads
Hover over a scheduled load time window for details and show load on ToU plot.
Show source data
| Tariff | Time of Day | Cost (AUD) |
|---|---|---|
| Daily Charge | 1.1660 / day | |
| Offpeak | 21:00 – 15:00 | 0.17270 / kWh |
| Peak | 15:00 – 21:00 | 0.30250 / kWh |
| 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 |
| Tariff | Time of Day | Cost (AUD) |
|---|---|---|
| Daily Charge | 0.891 / day | |
| Solar Soak | 11:00 – 16:00 | 0.14850 / kWh |
| Offpeak | 21:00 – 11:00 | 0.17930 / kWh |
| Peak | 16:00 – 21:00 | 0.33000 / kWh |
| Tariff | Time of Day | Cost (AUD) |
|---|---|---|
| Solar/Generation Feed in (4pm-9pm) | 16:00 – 21:00 | 0.03000 / kWh |
| Solar/Generation Feed in (9pm-10am, 2pm-4pm) | 21:00 – 10:00, 14:00 – 16:00 | 0.00100 / kWh |
| Solar/Generation Feed in (10am-2pm) | 10:00 – 14:00 | 0.00000 / kWh |
Daily supply charge Boost to 1 Aug: $1.16600, Boost 1 Aug – 10 Sep: $1.13300, GloSave from 10 Sep: $0.89100.
Usage and daily supply rates include GST. Feed-in rates are GST exclusive. Rates shown are before any conditional discount.
Solar is modelled rather than measured. Clear-sky global horizontal irradiance is computed from solar geometry for Melbourne (37.81°S, 144.96°E) on the 15th of each month, averaged across each clock hour, then scaled so the daily total matches the long-term mean daily global exposure for that month. Times are local clock time, so daylight saving shifts the curve. Every month is normalised against the annual peak hour. It represents sunlight falling on a horizontal surface, not the output of any particular rooftop system.
What are the key messages in these data?
- The cost of inaction and keeping my GloBird Boost plan after the 1 August 2026 price changes would have been substantial.
- The benefits in time shifting grid energy use can be significant and primarily in response to ToU peak pricing.
- Excess solar generation is not valued and should be avoided.
- Consider the ToU solar soak time window when designing and configuring your solar, battery, hot water, or EV charging systems
Ok, so decarbonisation? Discussions of ToU plans are naturally framed using costs as cost is the primary tool used to effect our energy use when using these plans. However, these relative ToU energy costs are also a strong signal for energy demand on the grid which is directly related to renewable energy generation here in Australia. Overlaying the estimated sunlight over our ToU plot should give you a good visual explanation for some of the reasoning behind the different ToU price tariffs.
The careful and considered timing of scheduled loads informed by our ToU energy plan enabled us to tune our systems for cost, which through the mechanisms shown above, means we are also getting the most out of our own solar energy generation, our own stored battery energy, and grid renewable energy. I’ve been careful not to use the term ‘optimise’ here as I think a pragmatic, considered approach will get us pretty close to where we want to be without fixating on the minutiae well past the point of diminishing returns. The breadth, degree, and timing of our own approach is probably quite varied (much like the deregulation of the Australian energy market). While this step is firmly in phase 2 of our decarbonisation project, it will continue to be part of the ongoing phase 3 that will allow us to adapt to changing needs, conditions, and most likely, change ToU energy tariffs.
References and resources
- Australia’s National Electricity Market after twenty years (griffith.edu.au/__data/assets/pdf_file/0030/1800687/No.2019-05-NEM-after-twenty-years-TN41.pdf)
- compare.energy.vic.gov.au (compare.energy.vic.gov.au)
- Open Electricity, formerly OpenNEM (explore.openelectricity.org.au)
- Price Discrimination by Negotiation: a Field Experiment in Retail Electricity (academic.oup.com/qje/article/137/4/2499/6570715)
- The tricks they use to stop us getting cheaper petrol (abc.net.au/listen/programs/the-economy-stupid/the-tricks-they-use-to-stop-us-getting-cheaper-petrol/106822272)
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