The tiered structure took effect on 1 May 2026. It exists to concentrate support on typical household batteries and to taper it for large ones.
The three tiers
| Tier | Usable capacity | Share of factor |
|---|---|---|
| 1 | First 14 kWh | 100% |
| 2 | 14 to 28 kWh | 60% |
| 3 | 28 to 50 kWh | 15% |
| None | Above 50 kWh | 0% |
Systems up to 100 kWh usable can still be installed under the program, but only the first 50 kWh earns certificates.
What each size earns in 2026
With the 2026 factor of 6.8 and a certificate price of about $39 (the market has been roughly $38 to $40 at the time of writing):
- 14 kWh: 95 STCs, about $3,700.
- 28 kWh: 152 STCs, about $5,900. The second 14 kWh adds 57 STCs, about $2,200.
- 50 kWh: 174 STCs, about $6,800. The last 22 kWh adds only 22 STCs, about $900.
From 1 January 2027, with a factor of 5.7 (5.2 from 1 July 2027), the three figures become about 79, 127 and 146 STCs.
How to use this when choosing a size
The rebate per kWh drops about 40 per cent after 14 kWh and about 85 per cent after 28 kWh. A larger battery may still make sense for a big household, a home with an electric vehicle, or backup, but the discount will not carry the extra cost the way it does on the first 14 kWh. Compare the extra hardware cost with the extra rebate.
An example of a tier trap
A household that wants 20 kWh of storage might compare a single 20 kWh battery with two 10 kWh units. Under the one-battery-per-property rule only one battery earns certificates, so the rebate is calculated on that battery alone. Check the rules before splitting capacity, because stacking smaller batteries may not behave as you expect.
What this means for you
Installers should present tiered quotes with the STC count shown, and homeowners should ask for it. See the per-kWh breakdown and the 1 May 2026 changes. The battery STC pillar and how it works cover the rest.