Sizing, Worked Examples and Quote Checklists
How to compare home battery quotes: a line-by-line method for the price, discount and fine print
Compare home battery quotes in Australia on net price per usable kWh, itemised extras, the STC discount shown, warranties, payment terms and installer accreditation.
Compare home battery quotes on net price per usable kWh, after checking that each quote includes the same scope of work. Put every quote into one table with the battery and inverter models, usable capacity, continuous power, gross price, number of STCs and price per STC, any state incentive, and itemised extras such as switchboard upgrades and backup hardware. Then compare warranty terms, the installer's accreditation, the payment schedule and the expected installation date — which sets the STC factor. Get at least three written quotes; a quote that cannot show these items in writing is harder to hold the seller to later.
All examples are illustrative. Use the quote and contract checklist and the installed cost estimator alongside this guide. For sizing first, see the sizing guide.
What every quote should contain
The Clean Energy Regulator (CER) requires solar and battery retailers to give written information before installation, including the contract, installer and designer details, system performance limits, feed-in tariffs and export limits, payback or savings estimates and any conflicts of interest. On top of that, ask for:
| Item | Why it matters |
|---|---|
| Battery brand and model, usable capacity (kWh) | STCs and your savings depend on usable kWh |
| Continuous and peak power (kW) | Whether it covers your evening loads |
| Inverter model and whether it is new or existing | VPP-capable and CEC-listed rule |
| Gross price | The starting point |
| STCs: number and price per certificate | So you can check the discount |
| State or VPP incentive, itemised | So you know what depends on a VPP contract |
| Extras: switchboard, backup gateway, three-phase, network application, travel | The most common source of later price changes |
| Expected installation date | Sets the STC factor |
| Warranties: battery years, throughput, end-of-warranty capacity, workmanship | Long-term value |
| Payment schedule | Deposit and when the balance is due |
| Savings estimate assumptions | So you can test them |
Build a comparison table
Illustrative example for three quotes for a household needing about 12 kWh usable:
| Quote A | Quote B | Quote C | |
|---|---|---|---|
| Usable capacity | 13.5 kWh | 10 kWh | 20 kWh |
| Continuous power | 5 kW | 5 kW | 7 kW |
| Coupling | AC-coupled | Hybrid (replaces inverter) | Hybrid |
| Gross price | $14,500 | $12,800 | $19,800 |
| STCs stated | 91 × $36 | 68 × $35 | 119 × $36 |
| Discount | $3,276 | $2,380 | $4,284 |
| Extras included | Switchboard, backup gateway | Switchboard only | None stated |
| Net price | $11,224 | $10,420 | $15,516 |
| Net per usable kWh | $831 | $1,042 | $776 |
| Battery warranty | 10 years | 10 years | 10 years |
| Workmanship warranty | 5 years | 2 years | Not stated |
| Deposit | 10% | 20% | 50% |
Reading it:
- Quote C has the lowest net price per kWh, but the household's overlap is about 12 kWh, so much of the 20 kWh is unused capacity. It also states no extras and asks for a large deposit. Ask what is excluded.
- Quote B includes a new hybrid inverter, which has value if the existing inverter is old, but has the highest price per kWh and a short workmanship warranty.
- Quote A matches the household's needs and includes the extras. For this household it is likely the best value despite not being the cheapest per kWh.
Net price per kWh is a starting point, not the answer. Match the capacity to your use first.
Checking the discount on each quote
- Multiply usable kWh (with the tiers above 14 kWh) by the STC factor for the expected installation date. For May–December 2026, the factor is 6.8. See the STC factor guide.
- Check the number of STCs on the quote is close to your figure. The CER's STC calculator gives the exact number.
- Check the price per STC. The CER describes a usual price of about $33–$38 but does not set it; a much lower figure means you are receiving less of the discount.
- Confirm what happens if installation slips into the next factor period.
Red flags in a quote
| Red flag | Why |
|---|---|
| No usable capacity stated | You can't check the discount or compare |
| "Rebate included" with no STC numbers | You can't check what you're getting |
| Very large deposit | Higher risk if the business fails |
| Battery much larger than your use | Sizing to the discount, not to you |
| VPP enrolment hidden in the fine print | Ongoing contract with its own terms |
| Pressure to sign today, or "rebate ends tomorrow" claims | The factor changes on set dates published by the CER; check them |
| No installer named | You can't check SAA accreditation |
| Payback estimate without stated assumptions | Can't be tested |
Payment and deposits
There is no official rule on deposit size, but smaller deposits reduce your risk. Many reputable installers ask for a modest deposit and the balance after commissioning. If a seller asks for most of the price upfront, ask why. If you are paying with finance, the finance contract is separate from the installation contract; see battery finance options.
If you signed at your door or after an unsolicited phone call, unsolicited consumer agreement rules apply, including a 10 business day termination period and a ban on taking payment during that time. See door-to-door and phone sales.
After you choose
- Check the named installer in SAA's accreditation lookup with a battery endorsement — see checking installer accreditation.
- Check the seller on the New Energy Tech Consumer Code approved seller list.
- Confirm the installation location meets AS/NZS 5139 — see battery safety and location.
- Read the contract terms on price changes and cancellations.
FAQ
How many quotes should I get?
At least three written, itemised quotes for the same capacity range. That gives you a sense of the spread and which items differ.
Is it normal for quotes to differ by thousands of dollars?
Yes, because of differences in inverter arrangements, extras, brands, warranties and margins. Itemised quotes show where the difference comes from.
Can I negotiate?
Yes. Use your comparison table to ask a preferred installer to match included extras or warranty terms rather than only the headline price.
Sources
- Clean Energy Regulator — retailer obligations, STC calculator
- New Energy Tech Consumer Code — approved seller search
- Solar Accreditation Australia — accreditation lookup
- ACCC — consumer rights when buying
