Buying a Perth house with existing solar: what to check before you settle

Buying a Perth home with an existing solar system is common — approximately 40% of WA homes now have rooftop solar. A functioning, properly documented system is a genuine asset. But a problem installation — poorly sized, incorrectly wired, or without the required paperwork — can create issues with insurance, DEBS registration, or grid compliance that fall to you as the new owner.

Here's what to check before settlement.

Step 1: Get the system documentation

Before anything else, ask the vendor (or their agent) for the installation documentation:

What should exist:

• Network Connection Notice (NCN) approval: Western Power's written confirmation that the system is approved for grid connection. This is not optional — without a lodged NCN, the system is technically not grid-legal.
• Electrical Safety Certificate (ESC): Issued by the licensed electrician who installed the system, certifying the installation meets AS/NZS 3000 (Wiring Rules).
• CEC Design and Installation Certificate: The Clean Energy Council certificate confirming the system was designed and installed by an accredited person.
• Warranty documents: Panel product warranty, panel performance warranty, workmanship warranty. Check names and dates.
• Inverter warranty: Separate from panel warranty. Typically 10 years from installation date.

If documentation is missing: A missing NCN is the most serious issue — the system may not be properly registered with Western Power, which can affect DEBS eligibility and create compliance risk. Ask the vendor to locate it before settlement. If it genuinely can't be found, a licensed solar electrician can assist with retrospective compliance steps, but it's extra cost and complexity.

Step 2: Check the DEBS registration

If the system is connected to Synergy's Distributed Energy Buyback Scheme, verify this on the vendor's Synergy account before settlement.

Key question: Is the DEBS registration in the vendor's name and attached to this property's Synergy account?

At settlement: DEBS registration transfers with the property address — but only if you open a new Synergy account for the property and advise Synergy of the solar system. The new account is not automatically on DEBS; you need to ensure the tariff is set correctly when you take over the account.

Action: When you contact Synergy to set up your account for the property, specifically request the DEBS tariff (or Midday Saver with DEBS, if applicable) and provide the NCN reference number.

Step 3: Get the system's performance history

Via the monitoring platform: If the inverter has online monitoring (Fronius Solar.web, Sungrow iSolarCloud, SolarEdge, Enphase Enlighten), ask the vendor to share access or provide an export of the historical generation data.

What to look for:

• Annual generation figures for the past 2–3 years
• Year-on-year trend (should be gradual decline, not sudden drops)
• Any extended periods of zero generation (inverter failure or disconnection)

Via the Synergy bills: Ask the vendor to provide 12 months of recent Synergy bills. These show export volume via DEBS, which combined with the generation monitoring data allows you to estimate self-consumption.

Sanity check: A 6.6kW system in Perth should generate approximately 9,500–10,500 kWh/year on a north-facing roof. If the vendor's data shows 6,000 kWh/year with no obvious shading explanation, something is wrong.

Step 4: Get an independent inspection

A CEC-accredited solar electrician can perform a professional inspection of the installation for approximately $150–$350. This is worth doing for any system more than 5 years old or if documentation is incomplete.

What a professional inspection covers:

• Electrical safety: DC cabling condition, connector integrity, earthing
• Roof condition: Panel mounting and racking integrity, roof penetrations
• Compliance: Whether the installation meets current standards (AS/NZS 3000, AS 4777)
• Inverter check: Fault history, current operation, age and remaining warranty life
• Generation verification: Comparing actual output to expected output for the system size

For older systems (installed pre-2017): Some older string inverters are approaching end of warranted life (10-year warranties). An inverter replacement costs $1,500–$3,000 depending on brand and size. If the inverter is 8–9 years old, factor this into your assessment.

Step 5: Check the panel age and brand

Panel age: Solar panels installed before 2016 used older cell technology (p-type PERC predecessors) with higher degradation rates (~0.5%/year or more). A 10-year-old system may have degraded 5–7% from its rated output. This is normal but factor it into your savings expectations.

Panel brand: Some brands that were active in the 2010–2018 Perth residential market have since exited or failed. A panel from a brand that no longer has Australian operations has:

• No product warranty support in practice (even if technically valid, there's nobody to claim from)
• No replacement panels available in the same wattage

Check the panel nameplate for manufacturer. A quick search confirms whether they're still operating in Australia.

Panel count and rating: Count the panels and check the rating (wattage stamped on the back or nameplate). With current panels, 16 × 415W = 6.64kW DC. An older system might be 20 × 250W = 5kW DC — still a reasonable-sized system, but different from a modern equivalent.

Step 6: Confirm the grid connection limit

Western Power's export limit in most Perth residential areas is 5kW per phase (single phase properties). Some areas have lower export limits, and properties near substations under constraint may be limited further.

For the property you're purchasing, ask Western Power (or a licensed electrician) to confirm the current approved export limit. If the system is exporting at 5kW AC on a 6.6kW DC array, that's normal. If the export limit was set lower (e.g. 3kW) due to area constraints, the system has been underperforming relative to its potential.

What to do if you find problems

Minor issues: Panels needing cleaning, a slightly underperforming string, an aging inverter still within warranty — negotiate a price adjustment or a vendor-funded inspection and remediation before settlement.

Significant issues: Missing NCN, non-compliant wiring, failed inverter — get a written quote for remediation from a CEC-accredited electrician and factor this into your offer price or settlement conditions.

Deal-breakers: A system installed by an unlicensed person (no CEC certificate, no ESC) may not be insurable and may need partial or full reinstallation. This is rare but possible with very old systems.

A working, documented solar system on a Perth property is genuinely valuable — it's generating $800–$2,500/year in electricity savings depending on size and usage. The pre-settlement checks above take a few hours and protect that value.