Terminology

• Module: framed glass panel of PV cells, rated in watts DC
• Array: group of modules on one roof area
• String inverter / microinverter / optimizer: DC-to-AC conversion options
• Rapid shutdown: reduces conductor voltage on the roof for firefighter safety
• Array boundary: limit used for rapid shutdown voltage
• Ballasted / attached racking: weighted low-slope systems or penetrating attachments
• Interconnection: connection to the service through a supply-side or load-side tap or breaker
• Net metering: utility credit for exported power
• Battery energy storage: stores PV output for backup and self-use

Standards

Ratings

• Rapid shutdown limits conductors outside the array boundary to 30 V within 30 seconds, and 80 V inside the boundary
• Roof access pathways and ridge setbacks: 18 in. on each side of a horizontal ridge for arrays up to 33 percent of plan roof area, 36 in. above that, with higher thresholds in sprinklered dwellings
• Roof fire classification maintained with the PV system

Test standards

• UL 1741 with IEEE 1547: inverters and interconnection equipment
• UL 2703: PV mounting systems and racking
• NFPA 70 (NEC): PV systems, rapid shutdown, interconnection, and storage
• ASCE 7: wind and snow loads on arrays

Components

• Modules: glass, cells, and aluminum frames
• Racking: aluminum or steel rails and attachments, or ballasted trays
• Inverters and optimizers: string, central, or module-level
• Rapid shutdown and disconnects: initiation devices and labeling
• Batteries: optional storage and backup gateways

Detailing

• Confirm roof structure for added dead load, ballast, and wind uplift
• Flash attachments into the roofing system; coordinate with roof warranty
• Keep fire access pathways, setbacks, and smoke vents clear
• Route conduit along roof edges and avoid crossing walkways
• Plan reroofing schedules; arrays are removed and reinstalled for roof replacement

Uses

Specific uses

• Single-family homes
• Warehouses and big-box retail with large low-slope roofs
• Schools and municipal buildings
• Multifamily and mixed-use buildings
• Net-zero energy buildings

Pros and cons

Pros

• On-site renewable electricity and lower utility bills
• Supports net-zero and energy code compliance
• Long module warranties

Cons

• Roof penetrations, loads, and reroofing complications
• Output limited by roof area, orientation, and shading
• Interconnection limits and changing incentives

Manufacturing and cost

Construction

• Racking and modules installed by solar contractors; electricians install inverters, rapid shutdown, and interconnection; utility approval before operation

Main manufacturers and suppliers

• First Solar
• Qcells
• Enphase
• SolarEdge
• IronRidge
• Unirac

Trade associations: SEIA and NABCEP.

Typical costs

• Residential rooftop PV, installed: about $2.50 to $3.50 per watt before incentives, with marketplace quotes near the low end

Sources

• Portlandia Electric Supply: NEC 2026 top changes solar installers must implement, https://www.portlandiaelectric.supply/blogs/electrical-accessories/nec-2026-effective-top-changes-solar-installers-must-implement-now
• SurgePV: NEC 2026 rapid shutdown, https://www.surgepv.com/blog/nec-2026-rapid-shutdown-solar
• Douglas County, CO: 2024 IBC Appendix Chapter Q solar access provisions, https://www.douglasco.gov/wp-content/uploads/2026/06/Exhibit-E-2024-Chapter-Q.pdf
• NRG Clean Power: solar installation cost guide 2026, https://nrgcleanpower.com/learning-center/solar-installation-costs/
• UL Standards: UL 1741 inverters and interconnection equipment, https://standards.globalspec.com/std/14568376/1741
• Wikimedia Commons: Rooftop Solar Panels 3KW.jpg, by Dr. Chinchu C. (CC BY 4.0), https://commons.wikimedia.org/wiki/File:Rooftop_Solar_Panels_3KW.jpg