15kWh
a 6.6kW to 10kW array is usually enough.
Residential
Large Home Battery Sizes: 15kWh to 50kWh
A big battery can carry a large home or a small business through the evening, the night and a good part of an outage. It can also be a poor way to store power you never use. Here is how to tell which one you are looking at, and what each size suits.
01
Do You Actually Need a Large Battery?
Sometimes, yes. Often, no.
Since May 2026 the federal rebate pays the full rate on only the first 14kWh of a battery. Every kilowatt-hour above that earns less, and above 28kWh it earns very little. That makes oversizing a worse deal than it used to be, and the market has moved: industry reports say average installed sizes fell sharply after April 2026.
- You use a lot of power after sunset, and your bills show it.
- You charge one or two electric cars at home overnight.
- You run a business, farm or workshop with heavy loads, or you pay demand charges.
- You want to ride out long outages without rationing power.
- Your solar array is big enough to fill it on an ordinary winter day.
If none of those fit, you will probably be better served by a battery under 14kWh, and we will say so at the quote stage.
02
kWh and kW: Two Numbers, Two Jobs
kWh is how much energy the battery holds. It decides how long you can run on stored power. kW is how much power it can deliver at one moment. It decides how many appliances can run together.
Searches for "30kW solar battery" and "50kW solar battery" are common, and they usually mean the capacity in kWh. A solar array is measured in kW and a battery in kWh, so a "30kW solar battery" is ambiguous. On this site the size in the page name is always the battery's usable capacity, and any solar array is named separately.
Usable capacity matters most. It is the figure the rebate is calculated on, and some brands advertise a larger nominal number. Compare usable kWh in writing.
03
How the Federal Rebate Treats Bigger Batteries
The Cheaper Home Batteries Program is delivered as small-scale technology certificates (STCs). Your installer claims them, so the discount comes off your invoice.
The rate itself, the STC factor, is 6.8 for batteries installed from May to December 2026. It falls to 5.7 on 1 January 2027 and keeps stepping down every January and July to 2030. What counts is the date the battery is installed, not the date you sign.
The program rules are published by the Department of Climate Change, Energy, the Environment and Water, and the certificate rules by the Clean Energy Regulator.
| Part of the battery | Share of the full STC rate |
|---|---|
| The first 14kWh | 100% |
| The next 14kWh (above 14, up to 28kWh) | 60% |
| Above 28kWh, up to 50kWh | 15% |
| Above 50kWh | Nothing |
04
What Shapes a Large Battery Quote
Every home and site is different. Your quote reflects your roof, switchboard, energy use, network rules and the equipment you choose, and we set it out in writing after a free assessment so you can compare it line by line.
05
Which Size Fits Which Property
These are starting points. Sizing from 12 months of bills or smart meter data beats any rule of thumb.
| Property | Typical fit | Page |
|---|---|---|
| Large family home, one EV, ducted cooling | 15 to 20kWh | 15kWh, 20kWh |
| Large home with pool, workshop and two EVs | 20 to 30kWh | 20kWh, 30kWh |
| Acreage or farm with water pumps and sheds | 30 to 40kWh | 30kWh, 40kWh |
| Café, clinic, small office or workshop | 20 to 50kWh | 40kWh, 50kWh |
| Anything above 50kWh | Commercial design | Commercial Solar and Battery |
06
What Changes When the Battery Gets Big
A 15kWh battery is a bigger version of a small one. A 40kWh battery is a different kind of job.
- Space and placement. Large batteries are heavy and often come as several modules. They need a suitable wall or floor, clearances and a location that meets the installation standard (AS/NZS 5139).
- Power supply. Bigger batteries are paired with larger inverters. Many large installs need a three-phase supply or an upgrade to get one.
- Switchboard and cabling. Higher currents mean heavier cable and sometimes a switchboard upgrade.
- Network approval. The connection application is part of the job, and some networks limit export or inverter size.
- Time on site. Expect longer installs than for a standard home battery.
We quote these items at the assessment, before you commit.
07
Solar Size Needed to Fill a Large Battery
A battery is only useful if you can charge it. A 10kW array averages about 38kWh a day in Sydney across the year and a 13kW array about 50kWh, on typical yield assumptions*. The house uses some of that during the day, so the rest goes to the battery.
20kWh
aim for 10kW or more.
30kWh
13kW or more, or you will often run short in winter.
40 to 50kWh
usually needs a commercial-scale array or deliberate grid charging on a cheap tariff.
See solar and battery packages for the array sizes.
08
Business and Farm Sites in NSW
If the site is a business, the battery may qualify for a separate NSW incentive from 1 September 2026, available for batteries from 20kWh up to 200kWh (BESS4) and above (BESS5). It runs alongside the federal rebate and has its own rules. See NSW Commercial Battery Incentive.
Equipment
Battery Brands We Install
We fit storage from manufacturers with local support teams, so the warranty on your battery still means something in ten years.
Batteries
Home and commercial storage, battery-ready where it makes sense.
Brand availability depends on your system design and location. We confirm the selected equipment and manufacturer warranty in your written quote.
Important Information
* Rebate details, output figures and timeframes shown are indicative estimates based on stated assumptions, not an offer, quote or guarantee. Your outcome depends on your site, roof, switchboard, network, products and the date of installation, and your written quote prevails. Savings and payback are not guaranteed. See clauses 24.1 to 24.5 of the Terms and Conditions.
Compare
Compare the Options
15kWh Home Battery
A 15kWh home battery and the federal rebate: how the tiered discount treats it, who it suits and how it compares with 20kWh.
20kWh Home Battery
A 20kWh home battery: who needs this size, how an EV changes the sums and what the tiered rebate means for it.
30kWh Battery
A 30kWh battery sits just past the 28kWh rebate line. See who it suits and how to size it for a home or business.
40kWh Battery
A 40kWh battery for large homes, farms and small businesses. See the NSW business incentive and what to check first.
50kWh Battery
A 50kWh battery is where the federal rebate stops. See what bigger batteries earn and the NSW business option.
Questions
Common Questions
01What Size Battery Do I Need for My House?
Start with your evening and overnight use, which your bill or smart meter shows. Add any planned EV or heat pump load, and check your solar array can fill the battery. Most homes need less than 14kWh. Larger homes, EV households and small businesses are where 15kWh and above makes sense.
02Is a Bigger Battery Always Better Value?
No. A bigger battery only pays off if you use the extra capacity.
03Why Does the Rebate Fall as Batteries Get Bigger?
From 1 May 2026 the program pays the full rate on the first 14kWh, 60 percent on the next 14kWh, 15 percent above 28kWh up to 50kWh, and nothing beyond that*.
04Can I Get a Rebate on a Battery Bigger Than 50kWh?
Batteries up to 100kWh nominal remain eligible, but STCs are only calculated on the first 50kWh of usable capacity*. Business sites in NSW may also access a separate state incentive.
05Do Large Batteries Need Three-Phase Power?
Often, yes, or at least a three-phase-capable inverter. We check your supply at the assessment.
06How Long Does a Large Battery Take to Install?
Longer than a standard home battery, because of the extra modules, cabling and approvals. We give you a timeline with your quote.
07What Happens If I Wait Until 2027?
It depends on your home, your site and the equipment you choose, so we confirm it in a written quote after a free assessment.