1. Usable capacity, not nominal
The rebate and your savings depend on usable capacity. Nominal capacity is always higher. Ask for the usable figure in writing and compare price per usable kWh.
2. Rebate eligibility
To get the federal rebate, the battery must be on the Clean Energy Council approved battery list, be new, be at least 5 kWh, be able to join a virtual power plant, and be installed with a new or existing solar system by a Solar Accreditation Australia accredited installer with a battery endorsement (Clean Energy Regulator).
3. The rebate shown on the quote
The quote should list the number of certificates (STCs) and the price per certificate the installer used. Check the number against the calculator.
4. Inverter
Some batteries need a hybrid inverter, others come with one or connect to your existing solar ("AC-coupled"). A new inverter can add thousands to the price. Ask whether your current inverter stays.
5. Warranty
Look at the length (often 10 years) and at what the battery must still hold at the end, usually a percentage of its capacity or a total energy throughput. A throughput limit can end the warranty early if you cycle the battery hard.
6. Blackout backup
Not every battery keeps the lights on during a blackout. If you want backup, ask whether it covers the whole house or selected circuits, and whether it costs extra.
7. Virtual power plant (VPP)
The battery must be able to join a VPP for the federal rebate, but joining is a separate choice. Some states pay more if you join (see rebates by state). Read the VPP terms: how much of the battery the operator can use, and for how long.
Quote checklist
| Ask for | Why |
|---|---|
| Brand, model, usable kWh | To compare like for like |
| STCs and price per STC | To check the rebate |
| Price before and after rebate | To see the real discount |
| Inverter: kept, replaced or included | Biggest hidden cost |
| Warranty years and end-of-warranty capacity | Real lifespan |
| Backup: none, some circuits, whole home | Blackout protection |
| Installer SAA accreditation number | Required for the rebate |