Solar Panels for New Builds 2026: What to Specify (and What Builders Won't Tell You)

Written by Jos Aguiar·April 2026·8 min

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Why Solar Comes Up in Every New Build Conversation

The NCC 2022 mandated a 7-star NatHERS energy rating for new homes in most Australian states and territories. That single requirement changed the new build solar conversation from "nice to have" to "almost always on the spec sheet." For most standard house designs, solar is simply the most cost-effective way to lift a 6-star design over the 7-star threshold, which is why builders began bundling it into packages as the default.

But default does not mean optimal. Builder-supplied solar, NCC compliance strategy, pre-installation decisions, and timing all have material effects on what you end up paying and what you end up with. This guide covers each of them.

The NCC 7-Star Requirement: What It Actually Means for Solar

The NatHERS rating is calculated using energy modelling software that accounts for the building envelope: insulation, glazing, orientation, shading, and air sealing. Solar generation counts toward the score, which is why it features so heavily in new build energy compliance.

The key point is that 7 stars is a minimum, not a target. A well-designed home in a temperate climate with good orientation, ceiling insulation above minimum, and double glazing on west-facing windows might hit 7 stars without any solar. A larger home, a less optimal orientation, or a budget build that skimps on the envelope may need solar to cross the threshold. Your building designer or certifier can tell you where your specific design sits before you commit to a solar package.

If the primary reason you are adding solar is NCC compliance, the minimum system that gets you to 7 stars is usually smaller than what makes financial sense to own. You may want to specify more capacity than compliance requires.

Builder Solar Packages: The Real Numbers

Builder solar packages are convenient. They are rarely a good deal. Here is why.

A builder's margin on a solar package is typically 30% to 60% above what you would pay sourcing and installing the same system independently. On a 6.6kW system, that premium is roughly $1,500 to $3,000. The markup exists because the builder takes a referral fee or operates under a volume deal with a specific supplier, eliminating price competition. You also have little visibility into what equipment is being installed until the system appears on your roof.

The mortgage financing point deserves attention. A $3,000 solar package premium rolled into a 30-year mortgage at 6% interest costs you roughly $6,500 over the life of the loan. That is the true cost of the convenience.

If you want solar through the builder, negotiate hard. Ask for the installer's CEC accreditation number, the brand and model of panels and inverter, the workmanship warranty duration, and the itemised solar cost separate from the build. If the builder cannot or will not provide these details, treat that as a red flag.

The Case for Waiting: Pre-Install, Then Decide

For many new build buyers, the best outcome is to pre-install the conduit infrastructure during the build and then shop for solar independently at or after handover. This approach has several advantages.

First, you will know your actual roof layout and orientation once the house is framed, and you can design the system around it rather than guessing at plan stage. Second, you have lived-in experience of your energy patterns once you move in, which means you can size accurately. Third, you are purchasing in a competitive market with transparent pricing rather than through a captive builder relationship.

The cost of pre-installation is low. Ask your builder or electrician to include:

• Conduit from the main roof space down to the switchboard location (20mm minimum, 25mm preferred)
• A draw string through the conduit so pulling cables later is simple
• A cable penetration through the roof in the correct position for your proposed inverter location
• Space in the switchboard for a solar isolator and, if you plan to add a battery, a battery management breaker

This conduit pre-install typically costs $300 to $600 added to the build. Without it, retrofitting the cable run through finished walls and ceilings later can cost $800 to $2,000 in labour alone.

What to Pre-Install While the Walls Are Open

While the builder has access to open wall cavities and roof space, it is far cheaper to add infrastructure for future upgrades than to retrofit later. Here is a checklist of what is worth specifying at build stage:

Three-Phase vs Single-Phase: Worth Upgrading at Build Stage

Single-phase power limits your inverter to 5kW in most states, which means a 6.6kW solar array generating above 5kW will have the inverter clip output. Three-phase connections allow inverters up to 10kW per phase and give you more flexibility for future additions including larger solar systems, batteries, and fast EV chargers.

Upgrading from single-phase to three-phase during a new build typically costs $1,500 to $3,000 extra and requires approval from the network operator. Retrofitting three-phase to a completed home costs $3,000 to $8,000 or more depending on distance from the street. If there is any chance you will own an EV or want a large solar system in the next decade, the build stage is the right time to install three-phase.

For townhouses with smaller roof areas and limited solar capacity, single-phase is usually sufficient since the roof will not support a system large enough to warrant three-phase anyway.

System Sizing for New Builds

The Federal Rebate Applies Exactly the Same as a Retrofit

New build installations are eligible for the Small-scale Technology Certificate (STC) scheme just like any other residential solar installation. The rebate is applied as a point-of-sale discount by your installer, so you see the post-rebate price on your quote.

On a 6.6kW system in Zone 3 (most east coast locations), the STC rebate in 2026 is approximately $2,800 to $3,400. In Zone 2 (Western Australia, parts of Queensland), the rebate is slightly higher due to greater solar irradiance. The rebate reduces by one deeming year each 1 January and the scheme ends in 2030, so earlier installations capture more value.

If your builder is quoting you the gross pre-rebate figure and presenting the STC as a builder discount rather than your federal entitlement, that is worth clarifying. The rebate belongs to you, not the builder, and should be clearly shown as a line item reduction in any legitimate solar quote.

The federal Cheaper Home Batteries Program launched July 2025 also applies to new builds. If you are adding a battery at or after handover, the roughly 30% discount (approximately $3,000 on a 10kWh battery) is available regardless of whether your home is newly built or decades old.

What to Put in Writing Before You Sign

If you are proceeding with builder-supplied solar, get the following confirmed in your build contract or a written addendum before signing:

• Panel brand, model, and wattage
• Inverter brand and model
• System size in kilowatts (DC capacity and inverter AC capacity)
• Number of panels and proposed roof layout
• Workmanship warranty duration (minimum 5 years, 10 years is better)
• CEC accreditation number of the installing company
• Whether conduit for future battery is included
• The itemised solar cost separate from all other build costs

If you are going the pre-install conduit route with independent solar at handover, confirm with your builder in writing exactly what conduit, penetrations, and switchboard space will be provided, and have this signed off before the electrical rough-in stage.

Written by

Jos Aguiar

Solar Evangelist

Passionate about making solar simple and accessible for every Australian household. Jos breaks down complex energy topics into practical advice so homeowners can make confident decisions about solar, batteries, and energy independence.

Learn more about Jos Aguiar