Solar arrays are designed to produce for decades. Asphalt shingle roofs are commonly expected to last twenty to thirty years. Put those two numbers next to each other and the sequencing problem is obvious, and yet it is routinely left out of the sales conversation because the installer sells solar rather than roofs.
The question is not complicated, but it is expensive to get wrong, and it needs answering before a contract is signed rather than after.
The Arithmetic
If the array will outlive the roof beneath it, someone will eventually pay to remove the panels, replace the roof, and reinstall the panels. That removal and reinstallation is a real cost, commonly quoted in the low to mid four figures depending on system size, roof complexity, and whether the original installer is still in business.
It also means an outage in production while the work happens, a second set of roof penetrations, and a warranty conversation between two contractors who may each blame the other for any subsequent leak.
Reroofing first avoids all of it. The cost of the roof is the same either way, only the timing changes.
A Working Rule
- Roof under about ten years old and in good condition. Go ahead with solar. The roof will likely need replacing near the end of the array's life, and by then removal and reinstall is a reasonable expense against decades of production.
- Roof roughly ten to fifteen years old. This is the judgment zone. Have a roofer assess it independently, not the solar company. If the assessment suggests fifteen or more years remaining, proceeding is defensible. If it is marginal, reroofing first is usually the cheaper path.
- Roof over fifteen years old, or showing wear. Replace first. The cost of doing it in the wrong order generally exceeds the cost of doing it early.
- Roof at or past its expected life. Replace first, without much debate.
The key is getting the roof assessed by someone with no interest in the solar sale. A roofer who is not bidding the solar job will give you a cleaner read, and photographs of the actual condition are more useful than an opinion. How to weigh the result is covered in roof repair or full replacement.
Which Roofs Suit Solar Well
Asphalt shingle is the easiest and least expensive to mount on. Standard flashed penetrations, familiar to every installer.
Standing seam metal pairs particularly well with solar. Panels clamp to the seams without penetrating the roof at all, which removes the main leak risk, and the roof itself will likely outlast the array. If you are replacing a roof and considering solar, this combination is worth pricing.
Exposed fastener metal requires penetrations and careful sealing but is workable.
Concrete and clay tile are more difficult. Tiles must be removed and replaced around each mount, tile is brittle, and breakage during installation and any later service is common. Installers charge more for tile, and some decline it. It is entirely doable with a crew experienced in it, and that experience is worth asking about specifically.
Slate is the most difficult and most expensive to work on, and many installers will not touch it.
Wood shake presents fire and durability considerations and is often unsuitable.
Flat and low slope roofs typically use ballasted or attached racking with tilt frames. Membrane condition matters a great deal, and penetrating a membrane roof requires correct detailing by someone who knows the system.
Structural Capacity
An array adds weight to the roof structure, modest per square foot but real, and it adds wind and in some regions snow loading through the mounting points.
Most jurisdictions require a structural review as part of permitting, sometimes a letter from an engineer. On older homes, homes with long rafter spans, or homes with undersized framing, reinforcement is occasionally needed. Better to know before signing.
Orientation, Shading, and What the Roof Can Actually Support
Not every roof plane is worth covering. South facing planes generally produce most in the northern hemisphere, with east and west facing planes producing less but still viable, and west facing sometimes preferred where evening peak rates apply.
Shading is the more common limiter. Trees, chimneys, dormers, and neighboring buildings all reduce output, and a small amount of shading can cost more production than people expect depending on the inverter configuration. Ask whether shading was measured on site or estimated from imagery.
Complex rooflines with many small planes, dormers, and valleys reduce the usable area and raise the cost per watt, since the crew installs more racking runs for fewer panels.
Doing Both at Once
Coordinating a reroof and a solar install in the same window has real advantages. One set of permits and inspections in some jurisdictions, one period of disruption, and the ability to have the roofer and the installer coordinate flashing details directly.
It also requires the two contractors to actually talk to each other and requires you to sequence them correctly, since the roof must be complete before the array goes on. Some companies offer both trades in house, which simplifies accountability. Ask who warrants a leak at a mounting penetration in that arrangement, and get the answer in writing. The distinction between workmanship and material coverage is explained in understanding workmanship and material warranties.
Broader coordination of multiple projects in one year is covered in sequencing multiple home projects in one year.
Questions for the Solar Installer
- What is your assessment of the roof's remaining life, and what is it based on?
- How are the mounts flashed, and what product is used?
- Who warrants a leak at a penetration, and for how long?
- What would removal and reinstallation cost if I reroof in ten years, and is that price documented anywhere?
- If the roof is replaced by another contractor, does that affect your warranty?
An installer who is comfortable putting an array on an aging roof without raising the question has answered a different question than the one you need answered.
Costs, exclusions, and how to compare proposals are covered in how to read a home solar quote.
If you want quotes for solar or roof replacement, tell us about your home and we will connect you with contractors serving your area. It is free to use, with no obligation to hire.