The arithmetic, which is the whole answer
A solar array has a service life measured in decades. An asphalt roof has one measured in years, and the years already run behind it.
Re-roofing under a live array is a three-party job: the solar company detaches and stores the panels and racking, the roofer replaces the roof, the solar company reinstalls and recommissions. The detach-and-reset is billed per panel and it is not cheap, and on some installations the warranty position gets complicated by who touched what.
So the question is never "does the roof need doing now". It is "will the roof need doing inside the array’s life, and what does it cost to do it then instead of now". Doing it now is almost always the cheaper of the two, and it is also the version where one contractor is accountable for the roof.
When the answer is clearly yes
The roof is fifteen years old or more, whatever it looks like. Asphalt does not fail gradually at the end; it fails at the seals and then quickly.
There is granule loss across the field, curling at the edges, or any creasing from wind. All three say the surface is near the end of its useful life regardless of whether it is leaking.
There are two layers up there. Anything bolted through a double layer is bolted through a problem.
The decking is soft anywhere, or previous flashing work has been done with sealant. Penetrations for racking need sound deck to land on.
When the answer is clearly no
The roof is under about five years old, was installed as a full system, and a measured inspection finds nothing. Go and put the array on it.
What is worth doing even then: have the roof looked at and photographed before the panels go on. Once an array is installed, the roof under it is much harder to inspect and much harder to claim on after a storm, and a dated pre-installation report is the record you will want.
The part most people miss: penetrations and warranty
Racking is attached through the roof, and every attachment is a penetration that has to be flashed properly rather than sealed. Done well it is a non-event; done with a bead of sealant it is a leak on a schedule.
Ask who warrants those penetrations. The solar company warrants its work, the roofer warrants the roof, and the seam between them is where a leak argument lives. Get both positions in writing before either job starts.
A manufacturer roof-system warranty can also have conditions about what is attached to the roof. Worth reading rather than discovering.
What we do here
We replace the roof and we document it, and we will tell you plainly if it does not need replacing — a free inspection that concludes "your roof is fine, go ahead with solar" is a perfectly good outcome and we would rather give you that than a job you did not need.
Free inspection across Maryland and Northern Virginia, usually within twenty four hours, with a photo report of every slope that is yours to keep and worth keeping if an array is going on top of it.
Get it looked at, free
We inspect across Maryland — Montgomery, Prince George's, Howard, Anne Arundel, Frederick, Carroll and Baltimore counties. Free inspection, photo report within 24 hours, and the report is yours to keep whether or not you hire us.