Panels last 25 years — does your roof?

A tier-1 solar panel is warranted to produce at least 84–87% of its rated power in year 25, and real-world field data suggests actual output at year 25 is often closer to 88–92%. The panels themselves outlast most household equipment, most cars, and most roofs.

This creates a scheduling problem. If you install solar over a 15-year-old metal roof that has 5–10 years of life left, you will need to remove all the panels, replace the roof, and reinstall them within a decade. The removal-plus-reinstall labor typically runs ₱40,000–90,000 depending on system size — money spent solely because the sequencing was wrong.

So the question worth asking honestly at the site visit is not “can we install solar on this roof” but “how many years of life does this roof have, and is that enough runway for the solar system to pay off before the roof needs work?”

Signs of a roof at end-of-life

Different roof types age differently. What to look for:

• Long-span metal: widespread rust bleed (not just surface stains but active pitting), widening of the seam gaps, soft or springy areas when walked on, visible corrosion at the ridge or eaves. A metal roof past 20 years and showing these signs is at end-of-life.
• Concrete flat-deck: visible cracks in the waterproofing membrane, standing water that does not drain, staining on the ceiling below, peeling or flaking of the membrane. A membrane past 15 years and showing wear is due for renewal.
• Concrete or clay tile: visible cracks in individual tiles, moss or algae in the tile joints, slipped or missing tiles, sagging in the tile field. Tile roofs past 30 years often need targeted replacement of failing tiles rather than a full replacement.
• Asphalt shingle: curling shingle edges, granule loss (visible bare-black asphalt beneath the granules), missing or torn shingles, moss growth in shaded sections. Shingles past 15 years and showing wear should probably be replaced before solar.

Ask your installer to walk the roof and give an honest assessment of remaining life. Ask them how many similar-age roofs they have installed on, and whether they carry warranty on the mounting penetrations for the full 25-year panel life or only for the roof’s estimated remaining life. Honest installers will say the second thing.

Option 1: Repair before solar

Repair before install makes sense when the roof has 15+ years of remaining life but has localized issues that are easier to fix now than to fix around a panel array. Common repair-first scenarios:

• Widespread surface rust on metal roof: sand, prime, and repaint the roof before installation. Cost: ₱30,000–80,000 for a typical residential roof. Extends life by 5–10 years.
• Cracked or worn waterproofing membrane on concrete flat-deck: strip and reapply a new elastomeric membrane. Cost: ₱200–400 per m². Extends life by 10–15 years.
• A handful of cracked or slipped tiles: individual tile replacement plus rebedding of the ridge tiles. Cost: ₱15,000–50,000. Standard tile maintenance rather than roof replacement.

The economics of repair-before-install are almost always favorable when the alternative is installing over a compromised roof and hoping. Small repair investments now protect the much larger investment in the panel array.

Option 2: Replace before solar

Replace-before-install is the right call when the roof is at or near end-of-life and repair would only buy 5–8 more years. Under this condition, installing solar directly on the old roof means paying the panel-removal-and-reinstall labor within the solar payback window — wiping out the payback advantage entirely.

Full metal roof replacement typical cost: ₱1,000–1,800 per m² for tier-1 galvalume or painted long-span. A 100 m² roof runs ₱100,000–180,000. Add ₱30,000–60,000 for gutter and fascia work if being done at the same time. Total for a typical residential roof replacement: ₱150,000–250,000.

Sequencing recommendation: do the roof replacement first, then the solar installation as a separate scope 2–4 weeks later. Trying to combine them into one contract usually adds project-management friction and rarely saves money — different crews, different trades, different insurance.

The one exception: if you were going to replace the roof within the next 3–5 years anyway (regardless of solar plans), pull it forward and combine it with the solar decision as a single capital allocation. Depreciating both roof and panels together often makes financial sense in a longer-hold ownership plan.

Option 3: Install anyway (rare cases)

Sometimes installing on a marginally aged roof is the right call. The pattern where this makes sense:

• Roof has 10+ years of remaining life — enough to hit solar payback before roof replacement
• Homeowner intends to sell within 5–10 years and is unlikely to be the party paying for the eventual roof replacement
• Roof replacement is prohibitively expensive relative to system size (large industrial or commercial roofs, where a full replacement is a five- or six-figure decision)
• Panel removal-and-reinstall cost is small relative to the value of solar production during the intervening years

In these cases, the installer should disclose the roof condition in writing, quote the panel-removal-and-reinstall cost for the future roof replacement upfront so it is not a surprise, and use non-penetrating mounting where possible (standing-seam clamps rather than bolted brackets).

What our site assessment looks at

A serious site assessment for a QC residential solar installation includes a roof condition inspection alongside the solar-specific measurements. Standard items on the checklist:

• Roof type, age, and estimated remaining life
• Rust, membrane, or tile condition — walked and documented with photos
• Rafter spacing, member size, and general structural condition of the roof framing
• Presence of asbestos in older asbestos-cement roofing (rare but seen in some pre-1990 QC houses) — asbestos requires abatement before any work
• Gutter, drainage, and eave condition — solar mounting cannot rely on a compromised eave
• Access — is the roof safely walkable for future maintenance, or does the layout create trapped sections

A quote issued without a roof condition report is a quote that has priced only the solar, not the whole job. Ask for the roof report as part of the site assessment — reputable installers include it as a standard deliverable.

Related guides

• Which roof types work best with solar in QC
• How much does solar cost in Quezon City?
• Typhoon-resilient solar installation in QC