How to compare solar quotes in Perth: an apples-to-apples guide

Getting three solar quotes from different Perth installers is consistently recommended advice. The harder part is comparing them. Most quote comparisons break down because the quotes are for different systems — different panels, different inverter models, different warranties, different inclusions.

Here's a structured method for making quotes comparable.

Step 1: Establish a common denominator — cost per kilowatt

Before comparing any other details, calculate the cost per kilowatt of DC capacity:

Formula: Quote price (after STC discount, ex-GST) ÷ total panel kW = $/kW

Example:

• Quote A: $7,800 for 6.6kW system = $1,182/kW
• Quote B: $8,500 for 6.6kW system = $1,288/kW
• Quote C: $6,900 for 6.6kW system = $1,045/kW

Note that $/kW is not a quality indicator on its own — it sets a basis for what you're paying relative to capacity, which then needs to be weighed against what you're getting.

Step 2: Check the panel specifications

Identify the exact panel model — not just the brand. "Longi 405W" is a specific product; "Longi solar panels" could be any of several models with different specifications.

Check these panel attributes:

• Wattage: Standard Perth residential panels in 2026 are typically 410–460W. Significantly lower wattage suggests older stock.
• Cell technology: PERC (p-type) or TOPCon/HJT (n-type). TOPCon panels have lower degradation rates — relevant for long-term output.
• Temperature coefficient: How much output drops per degree above 25°C. Perth-specific: lower is better. TOPCon typically ~0.30%/°C, PERC typically ~0.38%/°C.
• Performance warranty: What minimum output is guaranteed at year 25? Most panels warrant ≥80–84.8% of rated output. Check the specific minimum, not just "25 year performance warranty."
• Product warranty: 10–15 years for defects. 15 years is better; 10 years is minimum acceptable.

Step 3: Check the inverter specifications

Identify the exact inverter model. Inverter brand and model matter for:

• Warranty: Standard is 10 years. Some brands extend to 12 years; Enphase microinverters are 25 years.
• Efficiency: Most modern string inverters are 97–98.5% efficient. Avoid anything below 96%.
• Monitoring: Fronius, SolarEdge, and Sungrow all have good monitoring platforms. Check if monitoring is free long-term or subscription-based.
• Hybrid capability: If you plan to add a battery, a hybrid inverter (battery-ready) avoids the cost of a second inverter later.

Inverter oversizing: CEC allows up to 133% panel capacity to inverter AC capacity (e.g. 6.6kW panels on 5kW inverter). This is legitimate — peak output from Perth's panels frequently doesn't reach STC-rated capacity. But if one quote uses a 5kW inverter and another uses a 6kW inverter for the same panel capacity, understand the inverter is clipping at different thresholds.

Step 4: Check the warranty chain

Three warranties cover a solar installation. Verify all three:

| Warranty | Provider | Minimum acceptable | |---|---|---| | Panel product | Panel manufacturer | 10 years (15 years is better) | | Panel performance | Panel manufacturer | ≥80% at year 25 | | Workmanship | Installer | 5 years (CEC Code minimum) |

Ask: "If there's a problem with the installation in year 6, who do I call?" The answer should be the installer (workmanship warranty). If the installer says "call the manufacturer," the workmanship warranty is being misrepresented.

Step 5: Check what's included vs excluded

Inclusions to verify:

• [ ] Metering change / smart meter coordination (Western Power requires smart meter for DEBS — confirm this is handled)
• [ ] NCN lodgement with Western Power (mandatory for grid-connected solar)
• [ ] Connection to monitoring platform and setup assistance
• [ ] Removal of old solar system (if applicable — large extra cost if not included)
• [ ] Any roof repairs required (usually excluded — clarify in writing)
• [ ] Asbestos handling surcharge if applicable

Common exclusions that inflate apparent price differences:

• Switchboard upgrades (often needed for older homes — can be $300–$900 extra)
• Roof repairs for cracked tiles or flashing
• Extended inverter warranty (often offered as an add-on)

Step 6: Verify CEC accreditation

Any installer connecting solar to the grid in WA must be CEC-accredited. This is not optional — without CEC accreditation, the installer cannot lodge the NCN with Western Power, and you cannot claim STCs.

Verify: Search the CEC installer database for your quoted installer at cleanenergycouncil.org.au/installer-search. The accreditation number should match what's on the quote.

Step 7: Check estimated system yield

Most quotes include an estimated annual generation figure (kWh/year). Compare quotes on the estimated generation, not just the system size:

• A 6.6kW system on a north-facing 22° pitch in Perth should generate approximately 9,500–10,500 kWh/year
• A 6.6kW system on an east-west split should generate approximately 8,500–9,500 kWh/year
• If the estimated yield is unusually high (above 11,000 kWh/year for a standard 6.6kW system), ask how the estimate was calculated

Tool: Perth's BOM data gives approximately 5.0 peak sun hours daily average. A 6.6kW system at 85% system efficiency × 5.0 PSH × 365 days = approximately 10,200 kWh/year — use this as a sanity check.

What a good quote document looks like

A professional Perth solar quote should clearly state:

• Panel brand, model, wattage, and count
• Inverter brand, model, and capacity
• Mounting system (aluminium racking brand)
• System capacity (kW DC)
• Inverter AC capacity (kW)
• Price including GST, price after STC discount
• STC count used in the discount calculation
• Warranties (panel product, panel performance, workmanship)
• NCN lodgement included
• Estimated annual generation

If a quote is missing panel model, inverter model, or warranty terms — request an updated quote that includes them. Making decisions without this information is making decisions blind.

Getting three comparable quotes from CEC-accredited Perth installers, using this checklist, takes a few hours but can reveal significant differences in what you're actually getting for similar prices.