# Rooftop Solar PV

> Photovoltaic panels mounted on building roofs to generate electricity, and the roofing issues of load, attachment, waterproofing and roof life.

- URL: https://roof.wiki/rooftop-solar-pv/
- Topic: Climate, Hazards & Sustainability
- Also known as: rooftop solar; solar panels on roofs; roof-mounted PV
- Regions: Global
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Rooftop Solar PV." roof.wiki. https://roof.wiki/rooftop-solar-pv/

## Key facts

- **Typical module warranty:** 20-25 years
- **Median degradation (NREL):** About 0.5% per year
- **Output after 20 years:** Roughly 90% of year one
- **Main roof concerns:** Load, wind uplift, flashing, roof age

Rooftop solar photovoltaic (PV) systems use panels (modules) mounted on a building's roof to convert sunlight into electricity. Roofs are attractive sites because they are already built, are often unshaded, and are close to where power is used. Rooftop PV ranges from a few panels on a house to large arrays covering warehouse roofs.

## Roofing considerations

Installing PV turns a roof into a platform for equipment that will stay for decades, so the roof itself becomes part of the system's success.

- **Roof age and condition.** PV modules are typically covered by manufacturer warranties of 20 to 25 years and often keep producing after that. Removing and reinstalling an array to replace a roof partway through its life adds cost, so the US Department of Energy notes that a roof replacement can be a good time to add solar.
- **Structural capacity.** Panels and racking add weight, and some roofs designed only for their own weight need strengthening. Ballasted systems on flat roofs can add considerably more load than attached systems.
- **Wind loads.** Arrays experience wind uplift and drag; design pressures depend on location on the roof, with edges and corners most demanding. ASCE 7-16 in the United States added specific provisions for rooftop arrays parallel to the roof.
- **Waterproofing.** Each attachment point is a potential leak. Flashing details matched to the roof covering are critical.
- **Fire access.** Many jurisdictions require pathways and setbacks so firefighters can reach and ventilate roofs.
- **Snow and debris.** Arrays change how snow slides and where debris collects, which can affect gutters and drainage.

## Performance over time

NREL research found a median degradation rate of about 0.5 percent per year, so a typical panel produces roughly 90 percent of its first-year output after 20 years. Rates can be higher in hot climates and on rooftops, likely because of higher operating temperatures.

## Mounting approaches

- **Attached (penetrating) racks** on pitched roofs, bolted through flashed mounts into rafters or deck.
- **Clamp mounts** on standing seam metal roofs that grip the seams without penetrating the panels.
- **Ballasted racks** on flat roofs held down by weight.
- **Building-integrated PV (BIPV)**, where solar tiles, shingles or laminates replace part of the roof covering.

## Urban effects

Panels shade the roof surface below. A simulation of London's 2018 heatwave found that rooftop solar could reduce average outdoor temperatures somewhat (about 0.5 °C), though less than cool roofs in the same study.

## Policy

Several jurisdictions encourage or require rooftop solar, sometimes as an alternative to green roofs; for example, a 2015 French law required new buildings in commercial zones to be partly covered with plants or solar panels.

## Sources

1. Useful Life and Degradation of PV Panels (STAT FAQs Part 2) — National Renewable Energy Laboratory. https://www.nrel.gov/state-local-tribal/blog/posts/stat-faqs-part2-lifetime-of-pv-panels.html
2. Homeowner's Guide to Going Solar — US Department of Energy. https://www.energy.gov/eere/solar/homeowners-guide-going-solar
3. Photovoltaic mounting system — Wikipedia. https://en.wikipedia.org/wiki/Photovoltaic_mounting_system
4. ASCE 7-16 Wind for PV Parallel to Roof (SEAOC 2016 Convention presentation) — Solar Energy Industries Association. https://www.seia.org/sites/default/files/Cain%20and%20Banks%20ASCE%207-16%20Wind%20for%20PV%20Parallel%20to%20Roof%20Presentation%20-%20SEAOC%202016%20Convention.pdf