Solar and Battery Storage: Are You on the Right Electricity Plan?
Does a lower electricity rate always mean a lower bill? Once solar and battery storage supply most of a home's demand, the answer can change. Daily supply charges and feed-in credits may matter more than small differences in the price of electricity bought from the grid.
A new BillSave solar and battery case study explores this using August 2026 data from the Solar PV System in the IAMMETER Demo Account. It compares four selected Origin residential offers for Ausgrid: Go TOU, Weekday Shift, Night Shift and Solar Boost TOU.
This is a household Demo system with a battery-storage inverter, used for a controlled cost simulation. It is not a real customer's retailer bill.
Very little grid import, substantial export
For the 31-day month, the profile contains 19.10 kWh of grid imports and 557.94 kWh of grid exports. Inferred household consumption is 210.36 kWh, with the net inverter-side contribution covering approximately 90.9%.
That balance changes what matters when comparing plans. A cheaper import rate applies to only a small amount of electricity, while the feed-in structure applies to a much larger exported volume. Daily supply charges still accumulate throughout the month.
The inverter's 749.20 kWh AC output includes battery discharge; it should not be read as separately measured solar generation. The complete article explains the measurement boundary and how household consumption was inferred. You can also explore the IAMMETER Solar PV System Demo.
The higher feed-in credit changes the result
For this profile, Solar Boost TOU has the lowest modeled cost among the four selected offers: A$32.22, compared with A$38.49 for Go TOU.
Solar Boost's fixed and import charges are higher. Its additional feed-in credit more than offsets those costs. The selected version applies its higher credit to a billing-period allowance of 8 kWh multiplied by the number of billing days: 248 kWh for August, rather than an allowance that resets independently each day.
This does not make Solar Boost the best choice for every solar household. Different imports, exports and consumption times can produce a different outcome.
Remove system supply, and the comparison changes
The study also asks what would happen if the same inferred household consumption were supplied entirely by the grid, with no solar or battery supply. Under that scenario, Weekday Shift has the lowest checked modeled cost: A$106.38. Its discounted weekday daytime window covers more of this home's consumption than Night Shift's overnight window.
The scenario removes the whole system's supply contribution, not just the battery. The cost difference therefore cannot be treated as battery-only savings or an investment return.
All derived intervals are marked estimated. The source analysis discloses an unresolved incomplete-coverage quality label in the September 26 checks, despite no time gaps. These are checked modeled costs, not a platform-confirmed complete-bill ranking. Selected tariff versions are held constant for the experiment, including Shift versions effective from August 13; the figures are not historical payable bills. Solar Boost's no-solar result is only an arithmetic comparison, not evidence of eligibility.
Turn monitored energy data into a plan comparison
IAMMETER users can connect an authorised Cloud Site to BillSave and reuse their interval data. BillSave also works independently: users without an IAMMETER device can register by email and upload their own interval CSV.
Start with the complete solar and battery comparison, including the cost tables, offer links and downloadable scenario data. Then explore:
- Same usage, five electricity offers, for another household comparison.
- How to upload energy data, to prepare your own CSV.
- BillSave, to compare compatible offers using your own data and contract conditions.
