This solar battery calculator works out the battery to look at, what it costs installed in your city and the federal battery discount it gets. It is also a solar battery size calculator: it sizes the battery on the electricity you use after dark, the part of the day a battery covers.
Enter your after-dark use, or tap a common household to start.
Your measurements
Estimated cost, Australia
$8,000 to $15,000 typical $11,000
Your numbers
- Electricity you use after dark
- 10 kWh a day
- Battery size to look at
- 10 kWh usable
- Federal certificates (STCs), May to December 2026
- 68 at a factor of 6.8 per kWh
- Federal discount at $40 a certificate
- up to $2,720
- Yearly saving and payback
- Add your electricity price and feed-in tariff to see them
| Price row | Quantity | Rate | Low to high |
|---|---|---|---|
| Battery 10–13 kWh (mid-range) | 1 | $8,000 to $15,000 installed | $8,000 to $15,000 |
Rates are the low, typical and high figures in our solar price guide, prices verified October 2026. An estimate only: get quotes to price your job.
Type the total on your quote to see how it compares with this estimate.
This job in 15 cities: typical $9,900 in Hobart to $12,650 in Sydney
| City | Low to high | Typical |
|---|---|---|
| Hobart | $7,200 to $13,500 | $9,900 |
| Adelaide | $7,350 to $13,800 | $10,100 |
| Geelong | $7,450 to $13,950 | $10,250 |
| Newcastle | $7,600 to $14,250 | $10,450 |
| Sunshine Coast | $7,750 to $14,550 | $10,650 |
| Gold Coast | $7,850 to $14,700 | $10,800 |
| Brisbane | $8,000 to $15,000 | $11,000 |
| Darwin | $8,000 to $15,000 | $11,000 |
| Byron Bay | $8,400 to $15,750 | $11,550 |
| Melbourne | $8,400 to $15,750 | $11,550 |
| Perth | $8,400 to $15,750 | $11,550 |
| Townsville | $8,650 to $16,200 | $11,900 |
| Wollongong | $8,650 to $16,200 | $11,900 |
| Canberra | $8,800 to $16,500 | $12,100 |
| Sydney | $9,200 to $17,250 | $12,650 |
Each city is priced from the rows in its own guide, cheapest typical figure first.
Solar battery size calculator: how big a battery you need
A battery fills up from your panels during the day and runs the house after sunset, so the size that pays off is close to the electricity you use after dark. Smaller, and you still buy power at night; bigger, and part of it sits unused. These are the calculator's suggestions from the batteries in our solar guide, with the federal discount for a battery installed between May and December 2026.
| Household | Battery to look at | Discount | Installed price |
|---|---|---|---|
| Couple or small household, 5 kWh a day | 5 kWh usable | up to $1,360 | $5,000 to $9,000 |
| Family home, 10 kWh a day | 10 kWh usable | up to $2,720 | $8,000 to $15,000 |
| Big evening user, 13.5 kWh a day | 13.5 kWh usable | up to $3,640 | $12,000 to $17,000 |
How the calculation works
Size. A battery stores solar power from the day for the evening and night, so the size to look at is the electricity you use after dark. Your bill or your retailer's app shows your daily use; the share after sunset depends on your household. The example the calculator opens with is 10 kWh a day: 10 kWh usable.
The federal discount. Under the Cheaper Home Batteries Program a battery creates small-scale technology certificates (STCs) for its usable capacity, at the STC factor for the date it is installed. The Clean Energy Regulator's table sets 6.8 certificates per kWh for May to December 2026, 5.7 for January to June 2027 and 5.2 for July to December 2027. The full factor applies up to 14 kWh, 60% of it from 14 to 28 kWh and 15% from 28 to 50 kWh, and certificates are rounded down. The government's clearing house pays $40 a certificate (excluding GST), so the discount is up to that; installers usually take it off the price. The example battery earns 68 certificates: up to $2,720. The full rules are in our solar battery rebate guide.
WA. Synergy customers in Western Australia can also claim the WA Residential Battery Scheme: $130 per kWh of usable capacity up to 10 kWh, for a battery of at least 5 kWh. Pick Perth to see it.
Cost and payback. The price is the installed row in our solar guide for that battery in your city. Our guide does not say whether those prices are before or after the federal discount, so the payback is shown both ways. Each kWh the battery stores instead of exporting saves the difference between what you pay for electricity and your feed-in tariff.
Source for the figures that are not prices: Clean Energy Regulator (certificates per kWh of usable battery capacity by install date); Department of Climate Change, Energy, the Environment and Water (the capacity tiers and the clearing-house certificate price); WA Government (Energy Policy WA) (the WA Residential Battery Scheme rebate for Synergy customers), checked October 2026.
Federal battery discount by size (May to December 2026)
At 6.8 certificates per kWh, the capacity tiers and $40 a certificate.
| After-dark use | Battery to look at | Certificates | Discount |
|---|---|---|---|
| 4 kWh a day | 5 kWh usable | 34 | up to $1,360 |
| 5 kWh a day | 5 kWh usable | 34 | up to $1,360 |
| 8 kWh a day | 10 kWh usable | 68 | up to $2,720 |
| 10 kWh a day | 10 kWh usable | 68 | up to $2,720 |
| 12 kWh a day | 13.5 kWh usable | 91 | up to $3,640 |
| 13.5 kWh a day | 13.5 kWh usable | 91 | up to $3,640 |
Solar rates the calculator uses
These are the national figures from our solar price guide. Pick a city in the calculator and it switches to the same rows from that city's guide.
| Price row | Low | Typical | High |
|---|---|---|---|
| Battery 5 kWh (e.g. Sungrow) | $5,000 | $7,000 | $9,000 installed |
| Battery 10–13 kWh (mid-range) | $8,000 | $11,000 | $15,000 installed |
| Tesla Powerwall 3 (13.5 kWh) | $12,000 | $14,000 | $17,000 installed |
Solar prices by city
SydneyMelbourneBrisbanePerthAdelaideGold CoastCanberraHobartDarwinNewcastleGeelongSunshine CoastTownsvilleWollongongByron Bay
Frequently asked questions
What size battery do I need for my solar?
Size it on the electricity you use after dark. At 10 kWh a day the calculator suggests 10 kWh usable. A battery bigger than your evening use spends part of the night unused.
How much is the federal battery rebate?
It is a discount, not a cheque: certificates for the battery's usable capacity at the STC factor for the install date, worth up to $40 each. A 10 kWh battery installed between May and December 2026 gets 68 certificates, up to $2,720. The factor falls to 5.7 from January 2027.
Do I need solar to get the battery discount?
Yes. The battery has to be connected to a new or existing solar system; a battery that only stores power from the grid is not eligible. See our solar battery rebate guide for the full rules.
How much does a solar battery cost installed?
Our national solar guide lists a 5 kWh battery at $5,000 to $9,000 installed, a 10 to 13 kWh battery at $8,000 to $15,000 and a Tesla Powerwall 3 at $12,000 to $17,000. Choose your city in the calculator to use that city's figures.
How long does a home battery take to pay back?
Enter what you pay for electricity and your feed-in tariff. Each kWh the battery stores instead of exporting saves the difference, every day; the payback is the price divided by that yearly saving, shown on the typical price in our guide and on that price less the discounts.
How does a solar battery size calculator work?
It starts from the electricity you use after dark, because that is what a battery covers. At 10 kWh a day it suggests 10 kWh usable, the smallest battery in our solar guide that covers it.
An estimate is a starting point. Get quotes from local solar businesses to price your job.
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