Two quotes for "6.6 kW premium solar" can differ by four thousand dollars and ten years of service life. The difference is never in the headline — it's in five lines further down.
1. Panel make, model and quantity
You want the exact model number, not just a brand. Ask which tier the panel sits in and what the product warranty is (the warranty on the physical panel, separate from the performance warranty). Ten years is standard; twenty-five is a genuinely premium product.
2. Inverter make and warranty
The inverter is the part most likely to fail first. A five-year warranty on a budget string inverter tells you the installer expects to be back. Ten to twelve years is the mark of a system designed to be left alone. Microinverters and optimisers cost more but suit shaded or multi-face roofs.
3. Whether the rebate is already deducted
Most Australian quotes show the price after the small-scale certificate discount has been assigned to the installer. If one quote looks dramatically cheaper, check whether the other simply hasn't applied it yet. Comparing a post-rebate price to a pre-rebate price is the most common mistake households make.
4. What's excluded
- Switchboard or safety-switch upgrades — commonly $400–$900.
- Tile roof access, split-level or two-storey loading.
- Meter reconfiguration by your retailer.
- Long cable runs from roof to switchboard.
A quote with none of these listed is not a cheaper quote — it's a quote with variations still to come. Ask for them in writing before you sign.
5. Who actually does the install
Some companies sell nationally and subcontract every job. That's not automatically bad, but it changes who you call in year three. Ask whether the installing electrician is an employee, and whether the CEC accreditation number on the paperwork belongs to the person on your roof.
The one question worth asking
"If a panel fails in year eight, what exactly do I do?" A good installer answers with a process. A weak one answers with a brochure.