Solar for new builds: what to lock in before the slab is poured
Solar
Plan solar into the design stage, not after handover. It costs less to install, performs better, and sets you up to add a battery or EV charger without ripping into finished walls. The single most important move is requesting conduit runs and switchboard space at the pre-construction meeting, before your builder finalises the electrical plan.
Ask for three things at that meeting:
- A north-facing (or best-available) roof plane reserved and free of vents, flues or skylights
- 32mm conduit with draw wire from the roof to the switchboard
- Switchboard space and spare breaker slots for a future inverter, battery and EV charger
Your builder should already understand NatHERS 7-star requirements and how a CEC-accredited installer fits into the build sequence. If they don’t, that’s worth flagging early.
Key Takeaways
Planning solar during the design and construction stage rather than retrofitting after handover lowers installation costs, improves system performance and avoids costly rework later.
| Point | Details |
|---|---|
| Lock in conduit early | Request 32mm conduit with draw wire from roof to switchboard before walls close up. |
| Reserve switchboard capacity | Ask for external-wall placement with at least four spare breaker slots. |
| Time rebates carefully | STCs are handled at point of sale; property rebates often need your Certificate of Occupancy first. |
| Choose accreditation over price | A CEC-accredited installer protects your warranty eligibility and STC entitlement. |
| Work with a local specialist | Solar X Energy coordinates design-stage solar planning with builders across the Illawarra region. |
Table of Contents
- Why installing during construction pays off
- Rebates, STCs and when to actually claim them
- Roof design, orientation and structural checks that matter
- Conduit, switchboard placement and three-phase power
- How to size your system and what it costs
- How to choose a CEC-accredited installer
- Your pre-construction checklist
- Council rules and permits for new-build solar
- Solar and smart home integration
- Warranties and maintenance you’ll actually deal with
- Future-proofing for expansions and rising demand
- How grid connection actually works and what it costs
- Sources
- FAQ
Why installing during construction pays off
Solar bolted on after the fact almost always costs more. Retrofitting means scaffolding, roof penetrations through finished tiles, and running cable through walls that are already plastered. Doing it during the build means the roof is open, the frame is exposed, and an electrician is already on site.
A systematic analysis of Australian net zero homes found rooftop PV costs can be recovered in under four years when the system is designed well from the start, and that better insulation cuts HVAC energy use substantially when paired with solar. Get the envelope and the panels right together, and the payback curve steepens fast.
Pro Tip: Ask your builder to install 32mm conduit (not 25mm) with a draw wire already threaded through, and to leave physical space near the switchboard for an inverter. These three items cost next to nothing during a build but can cost hundreds to retrofit.
Rebates, STCs and when to actually claim them
Small-scale Technology Certificates (STCs) are the mechanism behind most of the upfront discount you see on a solar quote, and their value drops every year on a fixed schedule until the scheme winds down in 2030. Installers typically handle STCs at point of sale, deducting the value from your invoice rather than making you claim it separately.
Property-based rebates work differently. Most require your Certificate of Occupancy before you can apply, so the sequence looks like this:
- Construction completes and Certificate of Occupancy is issued
- You (or your installer) submit the rebate application within the eligibility window
- Installation proceeds once approval comes through
Solar Victoria’s guidance confirms new builds that include solar at the design stage see lower installation costs than retrofits. The common pitfall: signing off on the build before confirming whether your state’s rebate requires owner-occupier status at the time of application. Check this before you sign anything.
Roof design, orientation and structural checks that matter
Reserve a clear, unobstructed roof plane facing north, or the best available aspect, before the roof trusses go up. North-facing arrays in most of Australia perform best, but northeast and northwest orientations still deliver strong output, typically within 5 to 10% of true north. What kills performance is a roof cut up by vents, skylights, and plumbing stacks scattered across the only usable face.
Pitch matters less than people assume. Anything between 10 and 35 degrees works fine for most panel technology. What doesn’t work is a roof with no single face large enough to fit a meaningful array.
Structural checks worth requesting:
- Confirm truss specification accounts for panel dead loads, particularly for larger arrays over 10kW
- Ask whether extra purlins are needed for your roof type (tile roofs often need more than metal)
- Request an engineer’s check if you’re planning a battery-ready system with heavier ground or wall-mounted equipment
Shading is the other silent killer. A Builtly guide for new-home buyers recommends locking in a CEC-accredited installer during the design phase specifically so they can run a shadow analysis against your actual house orientation, not a generic template. Check neighbouring lots too. That two-storey house going up next door in three years will shade a roof plane that’s currently clear.
Pro Tip: If your roof design is complicated by dormers, skylights or a hip-and-valley layout, tell your designer early that you need one or two dedicated, unbroken roof faces reserved purely for solar. Retrofitting around an already-finalised roof plan is far harder than designing around solar from day one.
Conduit, switchboard placement and three-phase power
Run the conduit and size the switchboard now, while the walls are still open. This is the cheapest infrastructure decision in the entire build and the one most commonly skipped.
Industry guidance from xTechs Renewables recommends 32mm conduit as standard (not 20mm or 25mm), routed with a draw wire from the roof cavity straight to the switchboard location, minimising bends along the way.
- Request switchboard placement on an external or garage wall, not buried inside a robe or ceiling cavity
- Ask for at least four spare breaker slots, plus room for isolators, CT clamps and metering equipment
- Consider three-phase power if you’re planning a large array, a battery, or an EV charger. It gives headroom that single-phase supply often can’t, and retrofitting a three-phase upgrade later typically costs far more than specifying it during the build
Pro Tip: Get a data or LAN cable run hard-wired to wherever your inverter and switchboard will sit. Wi-Fi monitoring drops out constantly in garages and meter boxes; a wired connection means you’ll actually get reliable performance data.
How to size your system and what it costs
Most new builds land on one of three sizes: 5kW for smaller households with modest daytime use, 6.6kW as the current sweet spot for average family consumption, or 10kW for larger homes, homes with EV charging plans, or households running ducted air conditioning.
Cost varies by system size and equipment tier, but as a rough guide, Builtly’s 2026 figures put a 6.6kW system at roughly $5,000 to $8,000 after rebates, with 10kW systems scaling up from there depending on inverter brand and panel quality.
- If you’re planning a battery now or later, ask for a hybrid inverter or a battery-ready string inverter from a manufacturer like Sungrow, Fronius or Sigenergy
- Reserve wall space for a Tesla Powerwall or equivalent battery, and check it meets AS/NZS 5139 installation standards
- STC value declines every year through to the scheme’s 2030 end date, so earlier installation captures more rebate value in dollar terms
Comparing system size against your household’s usage before you lock in a build contract avoids the common mistake of sizing for today’s bills rather than tomorrow’s EV or ducted air con.
How to choose a CEC-accredited installer
Insist on a CEC-accredited installer using equipment from the CEC approved products list. Accreditation isn’t just a badge. It’s what makes your system eligible for STCs in the first place, and it’s what most manufacturer warranties require to remain valid.
Ask these questions before signing anything:
| Question to ask | What a good answer looks like |
|---|---|
| What’s your CEC accreditation number? | Given immediately, verifiable on the CEC’s public register |
| Which panel and inverter brands do you install? | Named brands like Sungrow or Fronius, not “whatever’s cheapest” |
| What warranty covers workmanship? | A clear written workmanship warranty, separate from panel/inverter warranties |
| Who physically does the install? | The accredited installer or their direct employees, not an unnamed subcontractor |
| Who handles grid connection paperwork? | The installer manages it as part of the quoted price |
Get at least three quotes, and ask each installer to itemise solar costs separately from the build contract so you can compare properly.
Your pre-construction checklist
Bring this to the pre-construction appointment and get each item confirmed in writing before you sign the build contract:
- 32mm conduit with draw wire from roof to switchboard
- Switchboard on an external or garage wall with four or more spare breaker slots
- One or two roof faces reserved, unobstructed, facing north or best available aspect
- Reserved wall space (roughly 1m by 1m minimum) for inverter and future battery
- A written shadow analysis if your block has neighbouring two-storey builds or mature trees nearby
Get this signed into the contract, not just verbally agreed. Verbal promises don’t survive a change of site supervisor.
Local installer perspective: practical tips from Solar X Energy
Coastal builds in the Illawarra need corrosion-resistant mounting hardware. Salt air eats cheap brackets within a few years. Strata-titled new builds often need body corporate sign-off before panels go up, so check that early, not after the array’s already ordered. See our local project updates for examples of recent installs.
Pro Tip: The most common fix we ask homeowners to make after handover is moving a bathroom exhaust vent that was placed dead centre on the best roof face. Flag vent placement with your builder before the roof frame goes up.
Council rules and permits for new-build solar
Most local councils treat rooftop solar on a new build as part of the standard development approval rather than a separate permit, provided the system sits within height and setback rules already covered by your building approval. Where it gets complicated is heritage overlays, bushfire-prone zones, and some coastal local environment plans that restrict roof-mounted equipment visible from the street.
Check your council’s development control plan before finalising the roof design, not after. Some councils cap the visible footprint of rooftop equipment on street-facing elevations, which affects where your installer can mount the array. If your block sits in a bushfire-prone area, additional compliance requirements can apply to cabling and equipment ratings.
Grid connection approval is a separate process from council permitting and runs through your local network distributor rather than the council. Your installer typically lodges this on your behalf as part of the standard installation process, and it’s one more reason accreditation matters. An unaccredited installer can’t lodge these applications through the proper channels, which can delay your connection by weeks.
If you’re building in a estate with a developer covenant, check the fine print. Some covenants specify panel colour, frame finish or mounting height for street presentation reasons, and ignoring them can mean a costly removal and reinstall after the fact.
Solar and smart home integration
A hybrid inverter with built in monitoring gives you the foundation for a proper home energy management system, not just a solar array that quietly does its own thing. Most current-generation inverters from brands like Sungrow and Sigenergy pair with an app that shows real-time generation, household consumption and battery state of charge side by side.
Where this gets genuinely useful is automation. Smart home systems can shift high-draw appliances, like pool pumps, hot water systems and EV chargers, to run when your panels are generating rather than at a fixed time. That’s a meaningful shift from “install and forget” solar to a system that actively reduces your grid draw.
If you’re planning this level of integration, specify it during the electrical rough-in stage. Smart switchboards and load-management devices need their own wiring and communication cabling, and adding them after walls are closed up means the same retrofit penalty you’re trying to avoid with solar. The wired LAN connection to your inverter mentioned earlier does double duty here: it’s also usually the backbone for whole-home energy monitoring.
Ask your installer directly whether their inverter and battery hardware supports third-party smart home platforms, or whether you’re locked into a single manufacturer’s ecosystem. This matters more the more automation you’re planning.
Warranties and maintenance you’ll actually deal with
Panels typically carry a 25 to 30 year performance warranty and a separate, shorter product warranty (commonly 12 to 25 years depending on manufacturer) covering manufacturing defects. Inverters run a different clock entirely, usually 5 to 12 years, because the electronics inside age faster than the panels sitting on your roof.
The warranty that actually protects you day to day is the installer’s workmanship warranty, typically 5 to 10 years, covering the mounting, wiring and installation quality rather than the equipment itself. This is the one that matters if a panel starts leaking at the roof penetration or a connector corrodes. Confirm this warranty is written down, not implied, before you sign.
Maintenance itself is minimal. A visual inspection once or twice a year, keeping panels reasonably free of heavy dust or debris, and checking your monitoring app for sudden drops in output are usually enough. Genuine faults tend to show up as a step change in generation data, which is another reason the wired monitoring connection mentioned earlier is worth the small extra cost during the build.
Keep every warranty document and the original compliance certificate somewhere permanent. If you ever sell the house, a documented, in-date system with clear paperwork is a straightforward selling point, and the research linking green features to a measurable resale premium backs that up.
Future-proofing for expansions and rising demand
Households change. A growing family, a pool, a home office, or an EV purchase down the track can all push electricity demand well past what your system was sized for at handover. The cheapest way to future-proof is deciding now, at rough-in, rather than trying to retrofit capacity into a finished home.
Oversizing your switchboard and conduit slightly beyond current needs is the single highest-leverage decision here. A 6.6kW system installed today can often be expanded later if the switchboard has spare capacity and the roof has room for more panels, but only if that headroom was planned for from the start.
Three-phase power, mentioned earlier for wiring, matters again here. If there’s any chance you’ll add an EV charger, a larger battery, or ducted air conditioning within five years, specifying three-phase during the build avoids a costly supply upgrade later. Battery capacity is another area worth over-speccing slightly. Battery prices tend to fall over time, so buying a slightly larger unit now, or leaving physical space for a second battery, tends to be cheaper than a full replacement in five years.
Ask your installer directly what expansion looks like with the specific inverter they’re proposing. Some hybrid inverters support adding a second battery module later; others require a full inverter swap. That single question can save you thousands down the track.
How grid connection actually works and what it costs
Grid connection is the process of formally linking your new system to the electricity network so excess generation can export and you can draw power when your panels aren’t producing enough. Your installer submits a connection application to your local network distributor, generally as part of the standard installation service rather than a separate cost you manage yourself.
Approval timeframes vary by distributor and system size. Smaller systems under a set export threshold often get fast, largely automatic approval. Larger systems, or homes wanting to export more than the standard limit, sometimes need additional network assessment, which can add weeks to the timeline.
Costs beyond the system itself typically involve a smart meter upgrade, which many new builds already have installed as standard, and in some cases a network connection fee charged directly by the distributor rather than your installer. These fees vary significantly by network area, so ask your installer to confirm them as part of your written quote rather than assuming they’re bundled in.
If you’re planning a system large enough to require three-phase supply, factor in that the network connection process for three-phase can take longer than a standard single-phase approval. This is one more reason to raise it with your installer and builder early, rather than discovering the timeline gap after your build is otherwise complete.
A note from the field
Homeowners who plan solar at the design stage almost always end up happier with the result. I’ve seen the difference between a system squeezed onto a roof full of vents and skylights versus one designed around a clear, dedicated array from day one, and it shows up in both output and how easy the system is to expand later.
How Solar X Energy can help with your new build
There are other ways to approach solar on a new build. Some homeowners go through their builder’s in-house package, others source an installer only after handover once the roof is already finished. Both work, but both usually mean less input into design decisions and higher costs when changes come later.
Solar X Energy coordinates directly with your build timeline, not after it. We work through tailored solar and battery packages designed around your roof, your switchboard plan and your household’s actual usage, rather than a generic builder add-on. Our team handles system design, pre-construction coordination with your builder, battery options if you want them now or later, and the local installation itself across the Illawarra region. If you’re still in the design phase of a new build, get a free solar quote and plan review before you finalise your build contract, so the right infrastructure gets locked in the first time.
Sources
- Cost benefits of net zero energy homes in Australia (systematic analysis)
- New builds slash costs with solar (Solar Victoria)
- Solar panels for new homes Australia: what to know before you build (Builtly)
- Battery information (Commonwealth energy regulator pages)
FAQ
Do new builds need solar?
Solar isn’t universally mandatory, but many jurisdictions require new homes to meet a NatHERS 7-star energy rating, and solar is often the easiest way to meet that standard without over-specifying insulation and glazing.
What is the 20% rule for solar?
Definitions of this rule vary by context and aren’t standardised nationally, so check with your installer or council exactly what threshold applies to your specific system size and location before assuming a fixed figure.
Is a 10kW solar system enough to run a house?
For most households, including those with ducted air conditioning or a growing family, 10kW comfortably covers daytime usage and leaves headroom for a future EV charger or battery expansion.
Why are people removing their solar panels?
Removal is usually tied to ageing, underperforming systems installed years ago with lower-efficiency panels, or a roof replacement that requires temporary panel removal, rather than dissatisfaction with solar itself.
