Why Price Comparison Fails
The average Australian household receives 3-5 solar quotes. Most compare on a single metric: total price. Some check the panel brand. A few look at the inverter. Almost none evaluate the seven factors that determine whether a system delivers its promised savings over 20 years.
Two systems with identical panel counts and identical prices can deliver wildly different outcomes — depending on these seven decisions.
Thing 1: System Size Is Not What You Think
Every quote lists a system size — "6.6kW" or "10kW." This refers to panel capacity under perfect laboratory conditions (25°C, 1000W/m² irradiance). Your panels will never produce their rated output in the real world.
Real-world losses:
- Temperature derating: -8% to -15% (panels lose efficiency above 25°C)
- Orientation losses: 0% (true north) to -25% (east or west facing)
- Shading losses: 0% to -40% (trees, neighbouring buildings)
- Soiling losses: -2% to -5% (dust, bird droppings)
- System losses: -3% to -5% (wiring, inverter efficiency)
What to look for: Estimated annual production in kWh (not just system size in kW), the assumptions behind that estimate, and whether a shade analysis has been performed.
Red flag: A quote promising specific annual production without a site visit or shade analysis is guessing.
Thing 2: The Inverter Matters More Than the Panels
Panels are commoditised. The difference between a $0.30/W and $0.50/W panel is 1-3% over 25 years. The inverter determines whether your system works at all.
| Factor | Premium (Fronius, SMA, Enphase) | Mid-Range (GoodWe, Sungrow) | Budget |
|---|---|---|---|
| Efficiency | 97-98.5% | 96-97.5% | 94-96% |
| Warranty | 10-15 years | 10 years | 5-10 years |
| Expected lifespan | 15-20 years | 12-15 years | 8-12 years |
| Battery compatibility | Extensive | Limited | Minimal |
| Failure rate (in warranty) | <2% | 3-5% | 8-15% |
The maths: A premium inverter costs $500-$1,500 more. A budget inverter failure at year 6-8 costs $2,000-$3,500 to replace. The premium inverter pays for itself by avoiding one replacement.
Thing 3: Workmanship Warranty > Product Warranty
Panels have 25-year warranties. Inverters have 10-15 year warranties. But these cover the product only — not the labour to diagnose, remove, replace, and recommission.
The installer's workmanship warranty covers:
- Roof penetrations and waterproofing
- Electrical connections and wiring
- Mounting system integrity
- Labour for warranty claims
Critical fact: Approximately 20% of solar installers operating in 2020 are no longer in business in 2026. A 25-year panel warranty is worthless if the installer who's supposed to action it no longer exists.
What to look for: Minimum 10-year workmanship warranty (5 years is the legal minimum — it's not enough), backed by insurance.
Thing 4: Roof Suitability Requires Physical Inspection
Not every roof can support solar safely. A typical 6.6-10kW system weighs 250-400kg.
What a proper assessment includes:
- Roof material and condition (tile, colorbond, flat)
- Truss/rafter spacing and timber condition
- Existing penetrations and their condition
- Planned roof maintenance timeline
Red flag: An installer who quotes without visiting your property cannot assess roof suitability. Remote satellite quotes are fine for initial sizing — installation should never proceed without physical inspection.
Thing 5: Network Export Limits
Your network operator has rules about how much solar you can export:
| Network | Standard Export Limit | Approval Required? |
|---|---|---|
| SA Power Networks | 5kW (single phase) | Yes — over 5kW |
| Ausgrid (NSW) | 5kW (single phase) | Yes — over 5kW |
| Endeavour Energy (NSW) | 5kW (single phase) | Yes — over 5kW |
| Energex (QLD) | 5kW (single phase) | Yes — over 5kW |
What this means: A 10kW system on single-phase may be limited to 5kW export. The remaining 5kW must be self-consumed or it's wasted. This doesn't mean 10kW is wrong — it means you need to understand how much you'll self-consume vs export.
What to look for: Has the installer checked your connection type? Applied for network approval? Modelled the impact of export limiting?
Thing 6: Monitoring Is Essential (Not Optional)
A solar system without monitoring is a car without a dashboard. You won't know if it's underperforming until your electricity bill arrives — months after the problem started.
What good monitoring provides:
- Real-time generation data
- Historical performance comparison
- Fault alerts
- Evidence for warranty claims
Why this matters for warranties: Without monitoring data, you can't prove underperformance. You're relying on quarterly bill comparisons — affected by weather, consumption changes, and tariff adjustments. Monitoring provides the evidence that makes warranty claims actionable.
Thing 7: Future-Proofing Saves Thousands
The system you install today needs to work with battery, EV charger, and heat pump you'll add in 5-10 years.
| Retrofit Item | Cost With Solar | Cost Later | Wasted Spend |
|---|---|---|---|
| Switchboard upgrade | $800-$1,200 | $1,500-$2,500 | $700-$1,300 |
| Three-phase upgrade | $2,500-$4,000 | $3,500-$5,500 | $1,000-$1,500 |
| Battery-ready wiring | $200-$400 | $800-$1,500 | $600-$1,100 |
| CT clamp installation | $150-$250 | $350-$500 | $200-$250 |
| Total potential waste | $2,500-$4,150 |
What to look for: Has the installer discussed your future plans? Is the inverter battery-compatible? Is wiring sized for expansion? Is the switchboard assessed for spare capacity?
The Quote Comparison Checklist
| Criteria | Quote A | Quote B | Quote C |
|---|---|---|---|
| Total price (installed) | |||
| Estimated annual production (kWh) | |||
| Panel brand + model | |||
| Inverter brand + model | |||
| Inverter warranty (years) | |||
| Workmanship warranty (years) | |||
| Installer years in business | |||
| CEC accreditation number | |||
| Shade analysis performed? | |||
| Physical roof inspection? | |||
| Network approval included? | |||
| Monitoring included? | |||
| Battery-ready? | |||
| Switchboard upgrade included? |
The Cable Co Difference
As a Vetted Tier 1 Contractor (not a solar-only installer), Cable Co approaches solar as one component of a broader electrification plan:
- We start with your energy data — not a panel catalogue
- We assess your entire electrical infrastructure — switchboard, supply, meter, network
- We size for your future — not just today's consumption
- We handle everything in-house — Level 2 ASP work, switchboard upgrades, network applications, solar, battery
- We model the 20-year economics — including degradation, tariff escalation, and future additions
Cable Co | 1800 117 177 | Vetted Tier 1 Contractor | ABN 64682354605