Rebates & Policy
Why a bigger battery doesn’t mean a bigger rebate
It is the most common assumption we correct, and the industry’s most persistent half-truth. The federal discount is tiered by size — and the tiers are front-loaded.
Published 24 September 2026 · Facts last verified 24 September 2026
Key points
- The federal discount is tiered by usable capacity: 100% of the factor for the first 14 kWh, 60% from 14 to 28 kWh and 15% from 28 to 50 kWh.
- Going from 27.84 kWh to 48 kWh adds 72% more storage but only 14% more certificates.
- A bigger battery can be the right choice for very high overnight usage or extended backup, but not for the rebate.
- The factor is 6.8 for installations completed in 2026 and 5.7 for installations from 1 January 2027.
Since 1 May 2026, certificates under the federal Cheaper Home Batteries program are calculated in three bands of usable capacity. The formula is simple: capacity in each band, times that band’s percentage, times the factor for the installation period (6.8 for installations completed in 2026).
| Usable capacity band | Share of the factor |
|---|---|
| 0 – 14 kWh | 100% |
| 14 – 28 kWh | 60% |
| 28 – 50 kWh | 15% |
Certificates are claimable only on the first 50 kWh of usable capacity, and the battery must be installed with rooftop solar, sit on the Clean Energy Council’s approved list, and be capable of joining a virtual power plant.
What the tiers do to a bigger battery
Run the formula across common capacities and the shape is unmistakable:
| Usable capacity | Certificates (at 6.8) | vs 27.84 kWh |
|---|---|---|
| 16 kWh | 103 | — |
| 24 kWh | 136 | — |
| 27.84 kWh | 151 | baseline |
| 32 kWh | 156 | +3% certificates for +15% storage |
| 40 kWh | 164 | +9% certificates for +44% storage |
| 48 kWh | 172 | +14% certificates for +72% storage |
Read that last row again. Going from 27.84 kWh to 48 kWh adds 72% more storage and earns 14% more certificates. Past the second tier you are paying close to full freight for every additional kilowatt-hour.
Why it is built this way
The program is designed to get as many homes as possible storing their evening peak — not to subsidise the largest possible battery in each home. The first 14 kWh does most of the peak-shaving work for a typical household, so that is where the support is concentrated.
If a proposal implies the discount scales with size — or prices a large battery as if it does — the arithmetic above is the check. Ask for the certificate count and the band-by-band working.
So how should you choose capacity?
On usage and backup, which is the boring, correct answer. Our sizing guide walks through it with real household bands. Large batteries have legitimate cases — very high overnight consumption, extended backup, three-phase properties with big loads — and every one of those cases justifies itself without leaning on the rebate.
One more date that matters: the factor steps down from 6.8 to 5.7 for installations from 1 January 2027, and the rate is set by installation date, not contract date. A quote that promises this year’s rate for next year’s install is promising something the rules do not allow.
Sources: Clean Energy Regulator — changes to the Cheaper Home Batteries Program · CER — solar batteries
Every figure on this page is checked against its primary source before publication. If a program or market figure changes, this page is updated and the verification date above moves with it.
Size it on your usage, not the discount
The Build Your System tool never inflates capacity to chase certificates. Four questions, honestly sized systems, indicative pricing with the rebate treated exactly as the rules define it.
