What size battery actually pays? Run your own Victorian home.
This calculator runs a Victorian home through a summer day and a winter day, hour by hour, with your usage and your solar. It shows what each battery size saves a year, the federal discount for each size now and from 1 January 2027, and the size where an extra kWh stops cutting your bill.
Written by Juan Flinn, Content Editor · Reviewed by the Mission Green Energy Team · Updated October 2026
Your home,
hour by hour.
Change any input and the table recalculates. Nothing you type leaves this page.
Not sure of your daily use? Divide the kWh on a quarterly bill by 91. A small Victorian home uses about 10.7 kWh a day, a medium one 14.9 and a large one 20.1.
| Battery (usable) | Saving a year | Extra vs smaller | Discount by 31 Dec 2026 | From 1 Jan 2027 |
|---|---|---|---|---|
| 5 kWh | $547 | — | $1,346 | $1,109 |
| 10 kWh | $795 | $248 | $2,693 | $2,257 |
| 13.5 kWh | $828 | $33 | $3,604 | $3,010 |
| 16 kWh | $828 | $0 | $4,079 | $3,406 |
| 20 kWh | $828 | $0 | $4,712 | $3,960 |
| 24 kWh | $828 | $0 | $5,386 | $4,514 |
| 28 kWh | $828 | $0 | $6,019 | $5,029 |
| 32 kWh | $828 | $0 | $6,178 | $5,188 |
| 40 kWh | $828 | $0 | $6,494 | $5,425 |
Why the saving
stops growing.
A battery can only save what your home would otherwise buy from the grid at night.
A battery earns money in Victoria by storing midday solar you would otherwise export for 0.8c and using it in the evening instead of buying power at 38c on a peak rate. Once the battery is big enough to cover your evening and overnight use on a good day, extra capacity has nothing left to shift. On a typical day it simply sits partly full.
That is why, for the default home in the table (14.9 kWh a day with 6.6 kW of solar), the saving climbs to about $795 a year at 10 kWh and stops near $828 from 13.5 kWh. More solar raises the ceiling, because there is more spare midday energy to store: the same home with 10 kW of solar and 20.1 kWh a day keeps gaining up to about 20 kWh.
The Midday Power Saver changes the picture a little. With three free hours from 11am to 2pm, the battery can also fill from the grid for nothing, capped at 24 kWh a day, so a plan with that window lifts the saving on every size.
What the federal discount
is worth on each size.
There is no Victorian state battery rebate. The federal Cheaper Home Batteries Program is the discount.
The discount is paid as small-scale technology certificates (STCs). A battery earns 6.8 certificates per usable kWh if it is installed by 31 December 2026, and 5.7 from 1 January 2027. The rate is tiered: the first 14 kWh count in full, 14 to 28 kWh count at 60%, and 28 to 50 kWh at 15%. Certificates are rounded down to whole numbers, and we value them at $39.60, the figure we credit on a Mission Green quote. The certificate price moves, so treat the dollars as a guide.
On a 10 kWh battery that is $2,693 now and $2,257 from January. On 20 kWh it is $4,712 now and $3,960 after. The install date decides the rate, not the date you sign.
How the model
works, and its limits.
Every input is published, and every limit is stated.
Solar is the PVGIS 5.3 hourly output for 1 kW of north-facing panels at 30 degrees in Melbourne, averaged for January and July. Your use follows the Victorian hourly load shape the ESC publishes from AEMO meter data, scaled to the daily figure you enter, and raised in winter and lowered in summer using AER benchmarks for Victoria. Prices are the 2026-27 Victorian Default Offer time-of-use rates for the CitiPower zone, or the Midday Power Saver rates if you tick the box, with a 0.8c feed-in tariff. Exports are capped at 5 kW, the battery charges and discharges at up to 5 kW, and it returns 95% of what it stores.
The year is a summer day and a winter day, each repeated until the battery settles, then averaged. It ignores cloudy runs, holidays, a heat pump or EV that changes when you use power, VPP payments and network tariffs outside CitiPower. It is a way to compare sizes, not a quote: a site inspection and your own meter data settle it.
Battery sizing:
your questions, answered.
For a typical Victorian home using about 15 kWh a day with 6.6 kW of solar, the bill saving stops growing at about 10 to 13.5 kWh of usable capacity. A larger home, more solar, an EV or a Midday Power Saver plan pushes that higher. Anything beyond it buys backup and VPP headroom rather than a lower bill.
On the 2026-27 Victorian Default Offer time-of-use rates, our model has a 10 kWh battery saving about $795 a year for a home using 14.9 kWh a day with 6.6 kW of solar, and about $828 at 13.5 kWh and above. A home using 20.1 kWh a day with 10 kW of solar saves about $1,167 a year from 20 kWh.
No. Solar Victoria’s rebate of up to $1,400 is for solar panels, not batteries. The discount on a battery in Victoria is the federal Cheaper Home Batteries Program, paid as small-scale technology certificates at the point of sale.
About $2,693 if it is installed by 31 December 2026, at 6.8 certificates per usable kWh and $39.60 a certificate, and about $2,257 from 1 January 2027, when the rate drops to 5.7. The certificate price moves, so the dollar figure is a guide.
A battery saves money by replacing grid power you would otherwise buy, mostly in the evening. Once it covers that on a typical day, the extra capacity has nothing to shift, so it sits partly full. More solar, more evening use or a free midday power window lets a bigger battery earn more.
If you are ready, yes: the same 20 kWh battery earns about $752 less discount from 1 January. But do not rush a design or an installer to beat it. The discount steps down every six months to track falling battery prices, and a badly sized or badly installed battery costs more than the step-down.
Where these
figures come from.
The model’s inputs are the same published sources used by the energy flow figure on our battery-charging guide. It is general information, not a quote or financial advice.