Battery size finder · 30 seconds
What size battery is worth it for you?
A few quick questions. We run every size from 5 to 30 kWh through a year of your home’s use and show where extra capacity stops paying.
Already have solar? See what a battery adds once you count the feed-in you give up
Ready to talk to an installer? Send a project brief without using the calculator.
Why size matters
The last kWh are the most expensive and the least used.
Australian homes have been installing batteries averaging around 28 kWh under the federal program. For many households, value flattens well before that: a battery earns money only on the energy it actually cycles each day.
The discount also tapers by size. Since 1 May 2026 it pays full value up to 14 kWh, 60% from 14 to 28 kWh and 15% from 28 to 50 kWh, so the extra kWh in a large battery cost you more as well as earning less.
Sources: Clean Energy Regulator, 18 March 2026 · Energy-Storage.news, 17 August 2026
Read the battery sizing guideQuestions
About the size finder
Why isn’t bigger always better?
A battery only saves money on the energy it actually stores and uses. Most homes use a set amount in the evening and overnight; once a battery can cover that on most days, extra capacity sits idle while still adding to the price. That’s the point where the bars in the chart flatten.
Does the federal battery discount change the answer?
The prices used are national average installed prices after the federal Cheaper Home Batteries discount (Solar Choice, August 2026 data). Since 1 May 2026 the discount pays full value for the first 14 kWh, 60% from 14 to 28 kWh and 15% from 28 to 50 kWh, so each kWh above 14 costs you more than the first 14 did. The discount per kWh also steps down every six months, next on 1 January 2027 (from 6.8 to 5.7 certificates per kWh).
Should I choose time of use?
If your plan charges more from 3pm to 9pm, choose time of use and enter your rates. A battery saves the most when it covers those dear hours, and we set it to hold charge for them where that saves more. In WA you can load Synergy’s Midday Saver rates with one tap.
How accurate is a 30-second answer?
It uses your state’s typical published rates and a typical usage pattern, so treat it as a strong starting point rather than a quote. The full assessment uses your own bill, plan and roof, and can read a PDF bill or smart-meter data.
Is anything I enter stored?
Your bill calculations stay in your browser and your answers are included in this page’s share link. Your postcode and requested services are sent to our server to check installer availability, without creating a lead. If you request a quote, we store and share only the details and brief you approve.