The top tier is where the rebate flattens. Capacity from 28 to 50 kWh counts at 15% of the factor, and anything beyond 50 kWh earns nothing.
The formula
For usable capacity from 28 to 50 kWh at the 6.8 factor, the STCs are 152.3 for the first 28 kWh plus 1.02 for every additional kWh (6.8 x 0.15), rounded down.
STCs and dollars, 2026
| Usable kWh | STCs (6.8) | Value at $38 to $40 | STCs in 2027 (5.7) |
|---|---|---|---|
| 30 | 154 | $5,852 to $6,160 | 129 |
| 40 | 164 | $6,232 to $6,560 | 137 |
| 50 | 174 | $6,612 to $6,960 | 146 |
Dollar values are indicative and based on the spot range at the time of writing. Use the battery STC calculator for your exact usable capacity.
What 30 kWh earns
Thirty kWh earns about 154 STCs, just 2 more than 28 kWh. The two extra kilowatt-hours add about $80. See 15 to 28 kWh for the band below.
What 40 kWh earns
Forty kWh earns about 164 STCs. Compared with a 28 kWh battery, the extra 12 kWh adds about 12 STCs, around $470. If a 40 kWh system costs several thousand dollars more than a 28 kWh system, the rebate covers only a small fraction of the gap.
What 50 kWh earns
Fifty kWh is the ceiling for certificates: about 174 STCs, or $6,600 to $7,000. Compared with a 14 kWh battery at 95 STCs, you receive about 80 more STCs for 36 kWh more hardware.
Cost after the rebate
After-rebate cost is installed price minus the STC discount. For 30 kWh that is the price less about $5,900 to $6,200; for 40 kWh, less $6,200 to $6,600; for 50 kWh, less $6,600 to $7,000. Because the discount is nearly flat across this band, the after-rebate price rises almost one for one with the hardware price. Large systems may need three-phase upgrades, extra enclosures and more complex approvals. See how a battery costs after the rebate.
What this means for installers
Large residential and small commercial batteries are the jobs where tier maths and usable capacity most often go wrong. Document the system’s usable kWh from the CEC data, the number of units and total capacity. See nominal versus usable. Our compliance desk pre-checks large systems, and you can see how settlement works at /start-trading/ and /pricing/.
What this means for you
The tier schedule exists to concentrate support on household-sized batteries. See why it falls above 14 kWh and the battery STCs pillar.