Builder-Installed Solar: Your Choice Or Theirs?

If you’re building a new home and assuming solar can be sorted out later, there’s something many buyers don’t realise until it’s too late: by the time it becomes a serious conversation, the important decisions may already have been made.

Can You Use Your Own Solar Installer For A New Build?

Builders often bundle solar into the build contract alongside everything else — flooring, lighting, appliances and air conditioning. But unlike most inclusions, solar can become tied to approvals, energy ratings, construction scheduling and site access rules. That’s why homeowners who assume they can simply “sort it out later” sometimes discover they have far less flexibility than expected.

As we’ve covered previously, getting a solar installer involved before the plasterboard goes up can save a lot of regret. In many cases though, the real issue starts even earlier — before the contract is signed.

Sometimes. But once a contract is signed, the builder usually controls the site, the trades and the agreed scope of works.

Before signing, buyers may be able to:

• remove solar from the contract
• negotiate different equipment
• arrange prewiring for future upgrades
• or organise their own installer

Getting the prewiring for solar right is far easier during the construction phase than later on.

After signing, things get much harder.

At that point, changes usually become contract variations. Builders may also refuse access to outside trades during construction for reasons involving scheduling, liability and warranty responsibility.

So while homeowners are not necessarily “forced” to use a builder’s installer in a legal sense, the practical reality is that the builder often controls what happens once construction is underway.

That’s the part many people don’t realise.

Why Do Builders Prefer Their Own Solar Systems?

Some homeowners assume builders only push bundled solar because it’s profitable. And there can certainly be margin built into these systems.

But there’s also a practical side.

Builders are trying to deliver a completed home on time, pass inspections and avoid delays. Solar interacts with roofing work, electrical rough-in, certification paperwork and final approvals. Using a standard installer and system makes that process simpler and more predictable.

The downside is that “builder solar” is often designed around getting the house finished efficiently, rather than optimising it for future electrification.

That’s one reason some homeowners end up disappointed with small systems that feel outdated quickly.

Are New Homes Actually Required To Have Solar?

This is where a lot of confusion creeps in.

Many homeowners are told solar is mandatory under energy efficiency rules, particularly in Victoria and NSW. But the reality is more nuanced.

New homes must comply with energy efficiency requirements under the National Construction Code (NCC). Depending on the state and design, rooftop solar can help achieve the required rating.

But that doesn’t automatically mean every new home is legally required to have solar panels.

In many cases, solar is simply the cheapest or easiest way for a builder to meet the standard. Better insulation, more efficient heating and cooling, improved glazing or upgraded hot water systems may also be used.

So homeowners sometimes hear:

“Solar is required”

when the more accurate explanation may be:

“This design relies on solar to meet the target rating.”

Why Tiny ‘Compliance Systems’ Keep Showing Up

This also explains why some new homes end up with small solar systems — sometimes around 3kW — even when homeowners plan to electrify heavily later.

If the system is mainly there to meet the energy rating, the builder’s priority is often simply achieving compliance at the lowest cost.

That can leave homeowners with systems that technically satisfy requirements but don’t match how the home will actually be used.

Later upgrades can also become more complicated than expected. A small inverter may need replacing entirely, roof layouts may not suit expansion cleanly, and homeowners can end up effectively paying twice.

If you’re planning solar on a new build, get it right from the beginning.

The Real Problem Is Timing

A lot of homeowners assume they can sort the solar out later — swap installers, upgrade the system, or replace the builder’s setup after handover.

But by then, the house design, approvals and construction schedule may already be based around that original system.

That’s why experienced installers often recommend getting solar advice early in the building process — ideally before contracts are finalised, not after the roof is on.

Because once construction starts, flexibility tends to disappear quickly.

What Should Homeowners Do?

The best time to think seriously about solar is before signing the build contract.

That doesn’t necessarily mean rejecting builder-installed solar. Some systems may be perfectly adequate. But it does mean getting clear on a few key things early:

• what is included in the build and how much can be changed
• whether solar is required as part of the home’s energy efficiency requirements
• how future upgrades like EV charging or batteries have been considered

Once construction is underway, options tend to narrow. What looks like a simple change can turn into a redesign of other parts of the build or a much more expensive variation than expected.

Don’t assume solar is something you can always “fix later”. Sometimes you can. Sometimes the build has already set the key decisions.

If you’re planning a new home and want to understand how solar fits into the design process before anything is finalised, it’s worth getting advice from installers who regularly work with new builds.

For more on getting solar right, read our deep dive guide on solar panels.