The arithmetic
Replacing the roof first costs the price of a roof.
Replacing it in eight years costs the price of a roof, plus removing the array, plus storing it, plus reinstalling it, plus new flashings and attachments, plus the production you lose while it is off. That work is covered in full on removal and reinstall.
There is no version where deferring is cheaper. The only question is whether the roof genuinely has life left.
How to judge remaining roof life
Age is a starting point, not an answer. What matters is condition, and a roofer should say so in writing rather than in conversation.
- Granule loss on asphalt shingle, especially collecting in gutters.
- Curling, cupping or cracking across a plane rather than in one spot.
- Previous repairs and patches, and how many.
- Decking condition, which is only visible once something is lifted.
- Existing leaks or staining anywhere in the roof structure.
Sequencing two trades
The roof goes on first, then the array. That part is obvious. What goes wrong is the gap between them.
The failure mode is a roofer finishing late or a solar crew booked three weeks out, leaving the homeowner chasing two companies who do not work for each other. Fix it contractually: agreed dates, agreed handover, and one named person responsible for the join.
If one company is doing both, that problem largely disappears — which is much of the value of a combined provider.
Liability, settled in advance
When a roof leaks near a solar attachment, two companies can each point at the other, and the homeowner is in the middle.
Ask explicitly: if water comes through within the workmanship warranty period, who investigates and who pays. Get the answer in writing from both parties before work begins. A company confident in its flashing will answer this without hesitating.
How the work runs
- Roof condition assessmentWritten, with remaining life stated — not a verbal opinion during a sales visit.
- Decide combined or sequentialOne provider for both, or two coordinated contracts.
- Agree the sequence and the datesIn writing, with a named person responsible for the handover.
- Settle the liability questionWho owns a leak at an attachment point, and for how long.
- Roof replacementIncluding any decking repair found once the old covering is off.
- Solar installationNew flashings into a new roof — the best conditions this array will ever have.
- Inspection and interconnectionThe normal path from here on.
What moves the price
We do not publish a national average and present it as your price. These are the variables that separate two quotes for the same job — run your own numbers with the cost guides and calculators, and check what incentives you actually qualify for.
| Factor | Why it moves the number |
|---|---|
| Roof size and material | The roofing job is the larger of the two costs on most homes. |
| Decking repair | Only discovered once the old roof is off. Ask for a per-sheet rate in advance rather than a surprise later. |
| Combined or separate contracts | One mobilisation and one point of liability usually costs less than two. |
| Roof complexity | Drives both trades at once — a complicated roof is expensive twice. |
| Timing | Doing it now against doing it later, where later includes a full removal and reinstall. |
What to ask before you commit
Take this list to the conversation. A professional who answers these directly is telling you a lot; one who deflects is telling you more.
- What is the remaining life of my roof, in writing?
- What is the per-sheet rate if decking repair is needed?
- Who is responsible if the roof leaks at an array attachment, and for how long?
- What are the agreed dates for each trade, and who owns the handover?
- Are you licensed for both the roofing and the electrical work, or is one subcontracted?
Common questions
Should I replace my roof before installing solar?
If it has under roughly ten years of life left, yes. Panels last around twenty-five years, so a roof that fails underneath them forces a removal and reinstall on top of the roofing cost.
Is it cheaper to do both at once?
Yes, in almost every case. One mobilisation, new flashings into a new roof, and no future removal and reinstall. The trade-off is a larger bill in a single year.
Can the same company do both?
Some do, and it simplifies liability considerably. Check they hold the licensing for both the roofing and the electrical work rather than assuming.
What if my roof only needs partial replacement?
Then the array should go on the planes with life left, if the design still works. A designer who ignores a failing plane to fit more panels is creating a problem for you.