Solar on new builds in Perth: planning it in from the start

Building a new home in Perth gives you an opportunity that existing homeowners don't have: designing the roof, electrical system, and orientation from the start with solar in mind. The decisions made at the building design stage — roof pitch, orientation, eave depths, battery provisions — affect solar performance for the life of the home.

Why solar in a new build is different

Cost advantage: Adding solar during construction allows you to include it in your building contract and potentially in your home loan (at home loan interest rates rather than a separate solar loan). Some builders include solar as a standard or optional inclusion. Even if solar is a separate contract, the scaffolding and roof access available during construction reduces installation cost by eliminating the need to re-scaffold.

Connection timing: The Western Power connection for a new build takes time — typically several months from the time you apply to when you receive your meter and can energise the property. Solar is installed and commissioned after the Western Power connection is live. Planning the solar installation early means you're ready to apply for connection as soon as the connection is active, rather than waiting months after moving in.

Design opportunity: In an existing home, you work with whatever roof you have. In a new build, you can make deliberate choices:

Roof design for solar

Orientation: A north-facing roof slope maximises annual solar generation in Perth. When working with your builder on house orientation, discuss whether the main roof slope can face north or within 30° of north. Many Perth lots accommodate this — the standard Perth lot runs east-west, allowing the main slope to face north.

Pitch: A 10–20° pitch is ideal for Perth. Perth's standard roof pitches (15–22°) work well. Shallower roofs (< 10°) generate slightly less in winter but are easier to install panels on. Very steep roofs (> 25°) are less common in Perth residential construction.

Roof type: Colorbond Trimdek or Klip-Lok (standing-seam) is the most common new Perth roof type. Solar panels install cleanly on both, using clamps that attach without roof penetration on Klip-Lok (zero-penetration installation, no leak risk). Concrete tiles and clay tiles are also common and install well.

Roof space: Ensure your roof plan includes enough continuous north-facing area for a viable solar system. A 6.6kW system needs approximately 35–40m² of unshaded roof area. A 10kW system needs approximately 55–65m²:

| System size | Approximate roof area needed | |---|---| | 6.6kW (20 × 330W) | ~35–40m² | | 10kW (25 × 400W) | ~50–60m² | | 13kW (30 × 440W) | ~60–70m² |

Hip roofs vs gable: Hip roofs have four sloping faces — the north-facing face is one of four. If the home footprint is deep (north–south), the north-facing hip face may be small. A gable end roof (two main slopes, north and south) often provides more north-facing area. Discuss with your designer.

Electrical provisions for solar

Ask your builder to include these provisions:

Inverter mounting location: The inverter (the device that converts DC solar power to AC household power) needs a mounting location with:

• Access to a wall in the garage, laundry, or exterior
• Within approximately 10–15 metres of the main switchboard (to minimise cable run)
• Shaded from direct afternoon sun (especially important for Perth summers — an inverter on a west-facing wall in direct sun will thermally throttle)

Confirm with your electrician that the inverter location is specified in the electrical plans.

Solar cable conduit: Your electrician can run conduit (empty cable pathway) from the roof to the inverter location during construction. This makes the solar cable pull during installation much simpler and cheaper — the solar cable runs through the pre-installed conduit rather than through roof cavities after construction.

Battery provision: If you're planning a battery now or in the future, specify:

• Battery mounting location (garage wall, laundry)
• A spare circuit in the switchboard for the battery connection
• A conduit from the switchboard to the battery location

Adding these provisions during construction costs approximately $500–800 extra in electrical work. Adding them after construction requires cutting into walls and re-cabling — significantly more expensive.

Switchboard upgrade: New builds should have a modern switchboard with circuit breakers (not fuses) and sufficient spare capacity for solar and battery circuits. Confirm with your electrician.

NatHERS and solar

The National House Energy Rating Scheme (NatHERS) rates new Australian homes for energy efficiency. Since May 2024, new homes must achieve a minimum 7-star NatHERS rating. Solar panels can contribute to the overall home energy rating but are not mandatory — the star rating primarily reflects the thermal envelope (insulation, glazing, orientation, shading).

A 7-star thermal envelope combined with a solar system creates a highly energy-efficient home — the tight thermal shell reduces heating and cooling load, and solar covers much of the remaining electricity need.

Connection and commissioning timeline for new builds

1. Builder applies for Western Power connection: typically 3–6 months before anticipated occupancy
2. Western Power energises the property: establishes the meter and account in owner's name
3. Solar installer commissioned: solar system installed and inspected
4. Network connection notification (NCN): installer submits NCN to Western Power for approval to connect to the grid
5. DEBS activation: Western Power activates DEBS feed-in credits on your account (can take 4–12 weeks after connection notification)

Plan for solar installation to occur within 4–6 weeks of Western Power energisation. This ensures you're generating electricity as soon as the connection is live, rather than missing weeks of generation while waiting for solar installation.

Builder vs separate solar contract

Builder-supplied solar (included in contract):

• Simpler: one contract, one point of contact
• Often a standard package from a preferred supplier — check the panel and inverter brands being offered
• May be included in home loan, reducing financing cost

Separate solar installer (outside builder contract):

• More choice of products and installer
• Competitive pricing — get quotes from 3+ installers
• Coordinate timing with builder to ensure solar installation occurs promptly after construction

Ask your builder which CEC-accredited installers they work with if using their preferred supplier — and check the equipment specifications (panel brand, inverter brand, warranty terms) before accepting the builder's package.

Western Power connection timelines and building energy standards apply to homes built in the SWIS network area. Confirm current requirements with your builder and Western Power for your specific lot.