Before You Install Solar Panels: 7 Things to Check About Your Roof

Your Solar Panels Will Outlast Your Roof — and That Is a Problem

Solar panels are warrantied for 25 years. Asphalt shingle roofs last 15–25 years. If your roof is 12 years old when you install solar, you will almost certainly need to replace the roof before the panels reach end of life — and removing and reinstalling a solar array costs $2,000–$5,000.

Checking your roof before signing a solar contract is not optional. Here are the seven things that determine whether solar makes sense on your roof.

1. Roof Age and Remaining Life

This is the most important check and the one most people skip.

For other materials:

• Metal standing seam: 40–70 year life — almost always fine
• Concrete tile: 30–50 year life — usually fine, but tiles are fragile under foot traffic during installation
• Wood shake: 20–30 year life — many solar installers will not work on shake roofs due to fire code and fragility
• Flat roof (TPO/EPDM): 15–25 year life — same calculus as asphalt shingles

The math: If you need to replace your roof anyway, do it before the solar install. Bundling the projects saves the $2,000–$5,000 removal/reinstall cost later. Some solar companies offer combined roof+solar packages that are cheaper than doing them separately.

2. Structural Capacity

Solar panels add about 2.5–3.5 pounds per square foot of dead load to your roof. A typical residential roof is designed for 15–20 psf dead load (the weight of the roof structure itself) plus 20–40 psf live load (snow, people walking on it).

Most roofs can handle the additional weight without modification. But there are exceptions:

• Older homes (pre-1970) may have been built to lower load standards
• Truss roofs with 2×4 top chords at 24-inch spacing are at the limit in some snow zones
• Flat roofs with low-slope membrane systems may need structural review
• Homes in high snow zones (upper Midwest, New England, mountain areas) where the roof is already near its design load with snow

How to check: Most solar installers will do a structural assessment as part of their site survey. If your home is older or you are in a heavy snow zone, ask for a structural engineer’s sign-off — it costs $300–$500 and can save you from a collapsed roof.

3. Shading

Solar panels need direct sunlight. Even partial shading on one panel can reduce the output of the entire string (depending on inverter type) by 20–40%.

Sources of shade to check:

• Trees — the most common and the most fixable
• Neighbor’s house or garage — not fixable
• Chimney, dormer, or roof-mounted equipment on your own house
• Power lines
• Future construction (empty lot next door that could sprout a two-story house)

How to assess: Use Google Project Sunroof (free, at sunroof.withgoogle.com) or the PVWatts calculator (pvwatts.nrel.gov). Both model your roof’s solar potential including shading. A solar access value below 80% means significant shading.

Trees: Trimming branches can improve output, but think about the tree’s growth over 25 years. A tree that barely shades the roof today will be 10–15 feet taller in a decade. If you are not willing to maintain the tree, factor in future shading.

4. Roof Orientation and Tilt

In the continental US, south-facing roofs produce the most energy. But east and west orientations are viable too.

Tilt angle: The ideal tilt roughly equals your latitude (30° in Dallas, 40° in Philadelphia, 47° in Seattle). Most residential roofs are 4:12 to 6:12 pitch (18–27°), which is close enough. Flat roofs use racking systems to tilt the panels.

If you only have north-facing roof area: Solar probably does not make financial sense on that portion. Focus on south, east, and west faces.

5. Roof Condition and Problem Areas

Even if the age is acceptable, specific conditions can make installation difficult or impossible:

Multiple roof planes: A complex roof with many valleys, dormers, and hips has less contiguous area for panels and more penetrations that could leak. Simple gable roofs are ideal.

Skylights and vents: Each obstruction reduces usable area and creates a shading source. Panels must be set back from skylights by at least 18 inches on most systems.

Existing leaks: If your roof leaks now, fix it before solar. The installers will make penetrations for mounting bolts — if the roof already has issues, those penetrations become additional leak risks.

Multiple layers of shingles: If your roof has two layers of asphalt shingles (a common practice when re-roofing over old shingles), many solar installers will not mount to it. The second layer is harder to seal around mounting bolts, and the roof is already near the end of its life. Building codes in most areas prohibit a third layer, so the next roof replacement requires a tear-off anyway.

6. HOA and Permit Restrictions

If you live in a homeowners association, check the rules before you sign anything.

The good news: Most states have solar access laws that prevent HOAs from banning solar panels outright. But HOAs can restrict:

• Panel placement (which roof faces can have panels)
• Panel appearance (black frames vs. silver, visible conduit routing)
• Installation methods (some require licensed installers, specific mounting systems)
• Total coverage area (some cap the percentage of roof that can be covered)

Check your HOA’s CC&Rs (Covenants, Conditions, and Restrictions) and architectural review process. Submit your solar plans for approval before installation. Most HOAs approve within 30–60 days.

If your HOA denies solar: Check your state’s solar access law. In many states, an HOA denial that contradicts state solar rights is unenforceable. The Solar Energy Industries Association maintains a state-by-state guide.

7. The Roof Replacement Timing Problem

This deserves its own section because it catches so many people off guard.

The scenario: You install solar at year 0. At year 13, your asphalt shingle roof needs replacement. The solar company charges $2,000–$5,000 to remove the panels, store them, and reinstall after the roofers finish. Your roof replacement costs $8,000–$12,000. Total: $10,000–$17,000.

The alternatives:

1. Replace the roof before solar. If the roof is 10+ years old, replace it first. Yes, you spend $8,000–$12,000 now instead of later. But you avoid the panel removal/reinstall cost, and you get 25+ years of roof life under your 25-year panels.

2. Use a solar-friendly roofing material. Metal standing seam roofs allow solar attachment without penetrations (panels clamp to the seams). If you are replacing the roof anyway, metal costs $10,000–$20,000 vs. $8,000–$12,000 for shingles — but you never drill holes in it for solar, and it lasts 40–70 years.

3. Negotiate a removal/reinstall clause. Some solar leases and PPAs include roof work coverage. If you own the system, ask the installer about a future removal/reinstall guarantee — some will lock in a price (typically $1,500–$3,000) for the first 15 years.

Quick Decision: Is Your Roof Ready for Solar?

If you pass all seven, schedule the solar site survey. If you fail two or more, the economics get worse — and you should fix the roof issues before committing to a 25-year solar contract.