Solar on a new build in Perth: what to specify before you break ground

The best time to make solar decisions for your Perth home is before the roof goes on. Decisions made at design stage cost a fraction of what they cost to retrofit — and some decisions (like roof orientation) can't be changed at all once the slab is poured.

The new build advantage

Building a new home gives you opportunities that existing homeowners don't have:

Roof design for solar: You can specify the roof pitch, materials, and orientation to maximise north-facing panel area. At Perth's latitude (approximately 32°S), north-facing panels at a tilt angle of 25–35° produce the most electricity annually. If you have design flexibility, maximise north-facing roof area.

No reroofing cost: Retrofitting solar on an existing roof sometimes requires removing and re-laying tiles around penetrations. On a new home, panels integrate with the roof from day one — lower installation complexity and no re-roofing disruption.

Electrical pre-wiring: During construction, running additional conduit and cable is cheap. After handover, the same work requires lifting flooring, cutting into walls, and significant labour. See below for what to pre-wire during the build.

Meter type choice: In a new build, you have the opportunity to specify a smart (interval) meter from the start. Smart meters record your electricity use in 30-minute intervals, which enables better tariff modelling, accurate monitoring, and full compatibility with time-of-use tariffs like Midday Saver.

What to pre-wire during construction

Work with your builder and electrician to include these items in the construction contract before handover. Retrofitting each of these after handover costs significantly more:

EV charger circuit: A dedicated 20–32A circuit from the main switchboard to the garage. Cost during build: $200–$500. Cost retrofit: $500–$1,200. Even if you don't own an EV today, EV ownership is growing rapidly and pre-wiring future-proofs the home at minimal cost.

Battery storage circuit: A battery system (whether installed now or in future) needs a dedicated circuit and often a separate meter point. Specifying the conduit run and termination point during construction means adding a battery later is straightforward electrical work, not a cable excavation.

Solar inverter location: Decide now where the inverter will go (typically the garage, a dedicated wall on the north side, or a ventilated utility space). Ensure the cable run to the switchboard and to the roof penetration points is included in the build scope.

Sub-metering: If you want granular monitoring of individual loads (EV charger, pool, main house), sub-meters can be installed during the electrical rough-in. Far harder to add later.

Roof orientation: the most important solar decision

This is the one that can't be undone. A few principles for Perth:

North-facing is optimal: Panels facing north receive the most direct sunlight year-round at Perth's latitude. If your block allows it, orient the main roof area to face north.

East-west split can work: Many narrow Perth lots (particularly suburban infill) can't achieve a pure north-facing roof. East-west split arrays (panels on both sides) generate less total energy than a pure north array but spread generation more evenly across the day — useful for morning and afternoon self-consumption.

South-facing panels: Significantly less effective in Perth (generating roughly 50–65% of an equivalent north-facing panel). Avoid placing primary solar panels on a south-facing roof section if alternatives exist.

Roof pitch: For Perth's latitude, a 25–30° pitch is close to optimal for annual generation. Flat roofs can use tilt frames, though these add cost. Standard suburban roof pitches (22–30°) are generally fine.

Shading: Specify where trees and shade structures will go before designing the roof layout. A large patio shade sail added post-solar over your north-facing roof is a significant lost-savings decision.

Builder solar packages: what to know

Most Perth volume builders offer solar packages bundled with the home. Some considerations:

Margin is often high: Builders make margin on solar packages as they do on other inclusions (appliances, tiles). The same system from an independent CEC-accredited installer often costs 15–30% less.

Specification can be vague: Builder packages sometimes specify "X kW system" without naming the panel brand, inverter, or warranty terms. Always obtain the full specification (panel brand and model, inverter brand and model, all warranty terms) before comparing.

Timing: Builder packages are typically installed just before handover. If you want an independent installer, confirm with your builder that you can source your own solar — some builders require you to use their solar packages as part of the build contract.

Quality control: Ensure whoever installs the solar is a CEC-accredited installer (not just a subcontractor without accreditation). The CEC accreditation is the licensing floor for solar installation in Australia.

The alternative: Accept the builder's basic wiring work (see pre-wiring above), defer solar until after handover, and obtain 2–3 independent quotes from CEC-accredited installers at that point. This often produces better pricing and equipment selection.

NatHERS energy ratings and solar

New homes in WA must meet a minimum 6-star energy rating under the National Construction Code (NCC) — assessed using the NatHERS (Nationwide House Energy Rating Scheme) methodology.

Solar panels themselves are not typically counted in a NatHERS rating (which focuses on thermal performance — insulation, glazing, ventilation). However, good solar orientation and passive solar design (window placement, eaves for winter sun/summer shade) can contribute to the thermal performance score.

The practical implication: meeting the 6-star NatHERS requirement is primarily about building envelope quality. Solar is an add-on investment on top of that base requirement, assessed on economic grounds rather than regulatory compliance.

Synergy connection for new builds

New builds require a separate Synergy connection application — this isn't automatic with the building permit. The builder or electrician typically lodges the connection application with Western Power, which physically connects the property to the SWIS network.

For solar, an additional grid connection notification or application is required once the solar system is installed. Your solar installer handles this as part of the installation process. The connection and DEBS registration can take 2–4 weeks post-installation.

Plan ahead: if you're moving into the home shortly after handover and solar is being installed around the same time, allow time for the connection process before expecting credits on your first bill.

A checklist for new build solar in Perth

Before signing your build contract:

• [ ] Review the roof plan for maximum north-facing roof area
• [ ] Check for tree placement that will create shading in 5–10 years
• [ ] Add EV charger conduit to electrical specification
• [ ] Add battery storage conduit to electrical specification
• [ ] Confirm solar inverter location in the electrical specification
• [ ] If taking builder's solar package: get full system specification (brand, model, warranty)
• [ ] If sourcing solar independently: confirm this is permitted under the build contract

After handover:

• [ ] Obtain 2–3 solar quotes from CEC-accredited installers if not pre-installed
• [ ] Register for DEBS with Synergy after installation
• [ ] Set up inverter app monitoring
• [ ] Apply for any STC rebate if builder hasn't applied it

Building codes and solar connection processes are subject to change. Consult your builder, licensed electrician, and solar installer for advice specific to your property and build contract. NatHERS requirements as per NCC 2022; check for any WA-specific amendments.