STC Calculator: How the Capacity Taper Affects Your Battery

Compare federal rebate values across each half-year period under the staggered step-down schedule. The capacity taper in force since 1 May 2026 significantly affects larger systems.

Your Battery Size

Enter your planned battery capacity to see timing impacts

Battery Capacity (kWh)

Common sizes: 10kWh (small), 13.5kWh (Tesla Powerwall), 20kWh (large), 40kWh (commercial)

Strategic Recommendations for Your 13.5kWh Battery

Good News: Full STC Entitlement

Your 13.5kWh battery sits in the 5-14kWh tier and receives 100% STC entitlement under the current framework. The annual factor reductions still apply, but the capacity taper does not.

Step-down schedule:

• Current (May-Dec 2026): 6.8 STCs/kWh
• 2027: 5.7-5.2 STCs/kWh
• 2028-2030: Continuing annual decline through scheme end

Additional Considerations:

• Most Perth installers have 2-4 month wait times — book early if you're aiming for a specific rebate factor
• Ask installers if they honour the STC rate at quote time or installation time
• WA state rebate (up to $1,300, 10kWh max eligible) is separate from federal STCs
• STC market price (~$39.9) can fluctuate, affecting final value slightly

Understanding the Capacity Taper

The Australian Government introduced tapered STC rates on 1 May 2026 to address taxpayer waste from oversized systems that would never fully cycle. The three-tier system, now in force, encourages right-sizing batteries to actual household needs.

5-14kWh Tier

100% STCs (optimal for most homes)

14-28kWh Tier

60% STCs (for larger households)

28-50kWh Tier

15% STCs (commercial/special cases)

Loading Solar Battery Perth...