Adding a battery to your existing solar
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Short answer: yes. The federal discount covers a battery added to solar you already have, as long as the battery is 5–100 kWh, on the CEC list and installed by an accredited installer [SB-S003, C]. What decides the cost is your inverter: keep it and add an AC battery with its own inverter, or replace it with a hybrid inverter that suits a DC battery [SB-S052, SB-S137, E].
Two ways to add a battery
| Keep your inverter (AC battery) | Swap to a hybrid (DC battery) | |
|---|---|---|
| Example | Powerwall 3: built-in solar inverter, AC output [SB-S052, C] | Sungrow SBR with a Sungrow hybrid [SB-S137, E]; FoxESS with a Fox hybrid [SB-S099, C]; Sigenergy with its own controller [SB-S060, E] |
| What changes | Battery goes in next to your system | Old inverter comes out; new hybrid runs panels and battery |
| Good when | Your inverter is young and working | Your inverter is old or due for replacement |
| Dated price example | Powerwall 3 $10,633–$12,633 after discount, as at Sep 2026 [SB-S061, C] | Sigenergy from $8,067.60 after discount, 18 kWh, as at 3 Nov 2026 [SB-S092, C] |
Whether your current inverter can talk to a given battery: MISSING (per-brand compatibility lists not read). Your installer must confirm it in writing.
Costs that catch people out
On one installer's dated list: switchboard upgrade up to $1,500 if needed; partial backup +$1,455.90 single phase; garage install +$500; cable runs over 5 m $30 per metre [SB-S092, C].
What the federal discount is worth
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.
10 kWh: 68 STCs, about $2,696. 13.5 kWh: 91 STCs, about $3,608 [SB-S036, SB-S001, SB-S095, E].
Who it's not for
- Homes with a small system that rarely exports: a battery needs spare daytime solar to charge [SB-S052, SB-S137, E].
- Anyone expecting to keep feed-in credits as well: power stored is power not exported [SB-S052, SB-S137, E].
Ask your installer
- Will my current inverter stay, and if not, why [SB-S052, SB-S137, E]?
- The battery model, usable kWh and CEC listing end date [SB-S026, SB-S071].
- Every extra as a line item: switchboard, backup, cable run [SB-S092].
Next step: get quotes
Ask at least two accredited installers for a written quote that shows the model, usable kWh and the certificate count.
Rebate rules in full: what the federal scheme pays for. Brands side by side: battery brands with dated prices.
Rules checked 3 November 2026. Next scheduled check: before 1 January 2027 (STC step-down), and monthly for WA and NSW.