This is the middle band of the tiered rebate. The first 14 kWh earn the full factor, and every kilowatt-hour from 14 to 28 kWh earns 60%.
The formula
For a battery of usable capacity between 14 and 28 kWh at the 2026 factor of 6.8:
STCs = (14 x 6.8) + ((usable kWh - 14) x 6.8 x 0.60), rounded down.
That is 95.2 for the first 14 kWh, plus 4.08 for each extra kWh.
STCs and dollars, 2026
| Usable kWh | STCs (6.8) | Value at $38 to $40 | STCs in 2027 (5.7) |
|---|---|---|---|
| 15 | 99 | $3,762 to $3,960 | 83 |
| 20 | 119 | $4,522 to $4,760 | 100 |
| 25 | 140 | $5,320 to $5,600 | 117 |
| 28 | 152 | $5,776 to $6,080 | 127 |
Values are indicative and use the market range at the time of writing. The battery STC calculator accepts any size.
The 15 kWh battery
Moving from 14 to 15 kWh adds only about 4 STCs, roughly $150 to $160. Many popular batteries sit near this edge, so a quote for a 15 kWh unit does not carry much more discount than one for a 13.5 kWh unit. See 5 to 13.5 kWh.
The 20 kWh battery
Twenty kWh earns about 119 STCs, or $4,500 to $4,800. The extra 6 kWh over 14 add about 24 STCs, worth about $930 to $980, so the incremental discount is about $155 to $165 per kWh instead of about $260 to $270 at the full rate.
The 25 kWh battery
At 25 kWh the figure is about 140 STCs. That is $5,300 to $5,600, with the extra 11 kWh beyond the first tier adding about 45 STCs.
The 28 kWh battery
Twenty-eight kWh is the top of this band: about 152 STCs, $5,800 to $6,100. Anything above 28 kWh earns only 15% of the factor. See 30 to 50 kWh.
Cost after the rebate
The cost after the rebate for a 20 kWh battery is the installed price less about $4,500 to $4,800. For 28 kWh it is the installed price less about $5,800 to $6,100. Hardware prices for large batteries are not linear and installs may need additional switchboard or wiring work, so compare quotes line by line. See how a battery costs after the rebate.
What this means for installers
Show the tier split on the quote, with the STC count. Lodge on usable capacity from the CEC list, and settle certificates at a published rate; see /pricing/, and /start-trading/ to set up.
What this means for you
Compare the extra price of the larger battery with the extra STC value in the table. The factor falls to 5.7 on 1 January 2027, which cuts every number above by about 16%. See the battery STCs pillar and why the rebate is smaller above 14 kWh.