The renovation checklist covers the builder, the design, the council approval, the budget, and the timeline. Solar almost never appears on it. For those who already have panels on the roof, that oversight can be an expensive one.
Four things change when a renovation happens around an existing solar system, and none of them is complicated to address. Yet all of them are harder and more expensive to fix once the build is finished.
The shading problem you’ll not see until it’s too late
A second-storey addition, a rear extension, or a new roofline changes the shadow profile of your property. Panels that had no obstruction before the build may be partially shaded for several hours each day after it.
This is most felt in winter. When the sun sits lower in the sky, shadows extend further and fall across roof areas that were clear through summer. A section of panels shading cleanly in December may lose 2-3 hours of generation each June day once the new structure is in place.
Even partial shading during the day reduces energy generation. In a standard string-inverter system, shade on one panel reduces the output of every panel in the same string. The financial impact compounds across years.
Australian councils require that a new extension not reduce a neighbour’s solar access below minimum standards, typically 2-3 hours of direct sunlight between 9am and 3pm on the winter solstice. There’s no equivalent rule protecting your own panels from your own renovation. The impact on your existing system is entirely your responsibility to anticipate.
The right time to raise this is before the plans are finalised. Ask your architect or designer to run a shadow analysis of the proposed structure against your existing panel positions. It identified whether panels need to be relocated, whether additional panels on the new roof can compensate for lost output, or whether a design adjustment can reduce the impact.
Done at the design stage, these changes are cheap. On the other hand, done after the build may involve a second round of work on a finished structure.
Roof work means panel removal, and most homeowners don’t know what that involves
Any renovation that touches the roof needs the panels to come off before work starts.
A roofer is not legally permitted to remove solar panels. That requires a licensed electrician. This is a fact most homeowners discover after signing with a builder or roofer who did not mention it. The panels must be electrically isolated and physically removed before roof work starts, then reinstalled and decommissioned once the roof is complete.
The realistic cost of solar coordination on top of roof work sits between $1,500 and $3,500 for a standard residential system. On a 20-panel array, removal and reinstallation run approximately $85 per panel plus GST. The roof work cannot begin until removal is complete, and panels should not go back on until roof coatings have cured, which adds 3-5 days to the timeline.
2 practical points worth knowing before you get to this stage:
- A system more than 10 years old has weathered mounting hardware and potentially corroded bolts. Removal takes 25-40% longer on older systems, which adds to the labour cost. That said, removal is a natural inspection point. The installer sees the underside of the array, the wiring condition, and the mounting hardware in a way that’s not possible during normal operation. If the system needs any remedial work, this is the cheapest time to address it.
- If your roof has less than 10 years of life remaining, replacing it before the renovation proceeds is significantly cheaper than dealing with a pane removal on top of a roof replacement later. The cost of removing and reinstalling panels a second time is an avoidable expense if the sequencing is planned in advance.
The electrical window most renovating homeowners miss
A major renovation almost always involves an electrician on site with walls open and conduit runs being established. That’s the right moment to future-proof the solar system’s electrical infrastructure, and most homeowners let it pass.
Pre-wiring for a battery system during the rough-in stage costs a fraction of what it costs as a standalone job later. Cable pathways can be established, conduit can be run to the intended battery location, and positions can be prepared while the walls are open. Coming back after the build to add battery storage means cutting into finished walls, patching, and repainting.
The same logic applies to a three-phase power upgrade. If the home is being significantly expanded and future EV charging or a larger solar array is possible, upgrading to three-phase during the renovation is cheaper than doing it as a separate job. Three-phase also increases the maximum size of solar system the home can accommodate, which matters if the renovation is creating additional roof space.
Ask your electrician during rough-in whether battery pre-wiring, a three-phase upgrade, or any switchboard work can be included while the structure is accessible. An electrician who’s not solar-aware will not raise these questions unprompted. The window to ask is before the rough-in stage is complete.
Your existing system may now be undersized
A renovation that adds a second storey, a granny flat, a home office, or significant new living space increases the home’s electricity demand. The system sized for a three-bedroom single-storey home may no longer be adequate for a five-bedroom two-storey home with additional heating, cooling, lighting, and power loads.
This is worth calculating before the renovation is complete rather than after the first power bill arrives under the new configuration. The new space adds climate control loads, lighting circuits, and additional hot water demand. If the existing system can’t cover the expanded load during the solar window, the household will draw more from the grid than it did before the renovation, which is the opposite of what most homeowners expect from a solar-equipped home.
A system assessment based on the renovation’s new floor area and intended use tells you whether expanding the solar array makes sense and whether the new roof area created by the renovation can accommodate additional panels. In many cases, the new roof space is a genuine opportunity to increase system capacity. Adding panels during the renovation, when the electrician and scaffolding are already on site, is cheaper than returning for a standalone installation after the build is complete.
4 conversations worth having before work starts
- Ask your architect or designer to check whether the proposed structure will shade any existing panels, particularly at the run angles typical of winter.
- Ask your builder whether roof work is involved and confirm the solar removal and reinstallation have been costed and assigned to a licensed electrician.
- Ask your electrician during rough-in whether battery pre-wiring, a three-phase upgrade, or switchboard work can be included while the walls are open.
- Ask your solar installer whether the existing system will still be appropriately sized for the expanded home, and whether the new roof area creates a case for increasing capacity.
None of these conversations is complicated. All of them are significantly cheaper than have before the build starts than after it finishes.
Before your renovation begins, a pre-build solar assessment can identify shading risks, system sizing gaps, and electrical upgrade opportunities while there is still time to act on them. Solar Service Guys carry out independent solar health checks and system assessments. Get in touch today.
