What size home battery do you need?
How this site makes money. We don't earn money from any links on this site yet. If that changes, we'll update this notice first. We don't compare every battery, installer or energy plan in the market. How we make money
Short answer: size it to the power you use after the sun goes down, not to your whole day. Look at usable kWh, not nominal. The federal discount pays full rate only up to 14 kWh, then 60% to 28 kWh and 15% to 50 kWh, so going bigger costs you more per kWh [SB-S001, C].
Sizes by brand (usable kWh)
| Brand | Step size | Range | Source |
|---|---|---|---|
| Alpha ESS SMILE-G3 | 9.3 or 9.6 | 9.3–57.5 | [SB-S074, C] |
| BYD HVS / HVM | 2.56 (HVS) | 5.12–12.8 / 8.28–22.08 | [SB-S056, SB-S073, C] |
| FoxESS EQ4800 | 4.66 | 9.32–41.93 | [SB-S054, C] |
| Sigenergy | 8.76 | per module | [SB-S060, C] |
| Sungrow SBR / SBH | 3.2 / 5.0 | 6.4–25.6 / 10–40 | [SB-S137, SB-S138, C] |
| Tesla Powerwall 3 | 13.5 | 13.5–54 | [SB-S052, SB-S070, C] |
How to size yours, in three steps
- Find your evening use. Your bill or retailer app shows usage by time of day; add up roughly 4 pm to the next morning (E). Typical household usage figures from a government source: MISSING.
- Leave headroom. Usable kWh is what you can draw; warranties assume the battery loses capacity to 70% over 10 years [SB-S053, SB-S050, C], so a battery that just fits today may fall short later [SB-S053, SB-S050, E].
- Check the step. Some brands jump in big steps (Alpha ESS 9.3 to 18.6) and others in small ones (Sungrow 3.2) [SB-S074, SB-S137, E].
How size changes the discount
Our arithmetic, not a quote: installs from May to December 2026 earn 6.8 STCs per usable kWh up to 14 kWh, then 60% of that to 28 kWh and 15% to 50 kWh [SB-S036, SB-S001, C]. STCs last traded at $39.65 (30 Oct 2026); installers pass on a bit less [SB-S095, C]. The factor drops to 5.7 for installs from January 2027 [SB-S036, C]. The discount is set by the installation date [SB-S004, C]. It needs a CEC-listed, VPP-capable battery installed with solar by an SAA battery-endorsed installer [SB-S003, C]. The STC price moves, so your installer's figure will differ. Official rules: cer.gov.au and dcceew.gov.au.
| Usable kWh | STCs | About |
|---|---|---|
| 10 | 68 | $2,696 |
| 14 | 95 | $3,767 |
| 20 | 119 | $4,718 |
| 28 | 152 | $6,027 |
[SB-S036, SB-S001, SB-S095, E]
What people are buying
From 1 Jul 2025 to 30 Sep 2026, 546,789 batteries went in under the program [SB-S075, C]. Average size: MISSING (not read from that table).
Who a big battery is not for
- Homes whose solar can't fill it on a winter day [SB-S053, SB-S050, E].
- Anyone sizing for blackouts alone: backup circuits matter more than kWh [SB-S053, SB-S050, E].
Ask your installer
- The usable kWh on the CEC list for the exact model [SB-S026].
- How they sized it from your usage data.
- What a smaller and a larger option would cost.
Next step: get quotes
Ask at least two accredited installers for a written quote that shows the model, usable kWh and the certificate count.
Rules checked 3 November 2026. Next scheduled check: before 1 January 2027 (STC step-down), and monthly for WA and NSW.
Each brand's step size changes what you pay for, so see how the brands compare on step size and dated price before you pick a size. Rebate tiers in full: the discount tiers by size.