What Should Commercial Solar PV Design Cover, Start to Finish?

Commercial solar PV design covers feasibility and shading analysis, array layout and electrical design including inverter selection and interconnection, structural verification of roof loading and wind uplift, utility interconnection applications, permitting, and commissioning — coordinated across electrical, structural, and roofing disciplines from the start. The mistake I see most often is treating solar as an electrical add-on instead of a building project. The array touches the roof structure, the roof warranty, the electrical service, the utility's grid, and the fire code's access requirements. Designing it as an electrical package with the other disciplines informed late produces the change orders. Designing it as a coordinated building system from feasibility onward produces a system that performs.

Feasibility sets the foundation: a shade study modeling parapets, rooftop units, and neighboring buildings across the year; a structural screening of roof capacity; the building's interval load data matched against modeled production; and the utility's interconnection queue, tariffs, and export rules. A feasibility study that skips any of these is a guess. Design development then produces the real engineering: optimized array layout balancing energy production against fire code setbacks and maintenance access; string sizing matched to inverter voltage windows across temperature extremes; conduit and wire sizing with voltage drop calculations; the point of interconnection — line-side tap, load-side breaker, or dedicated service — coordinated with the utility; structural calculations for gravity, wind, and seismic with attachment details the roofer can build; and a monitoring and commissioning plan so the owner can verify the system produces what was promised.

Solar underperformance is almost always a design or installation issue, not a panel issue. These are the checkpoints that keep a commercial array honest.

• Model shading honestly: parapets, units, and seasonal sun angles in the production estimate, not just the panels
• Verify structure in feasibility: roof capacity for dead load, ballast, wind uplift, and seismic before equipment is ordered
• Protect the roof warranty: attachment and flashing details approved by the roofing manufacturer
• Design for fire access: ridge setbacks, access pathways, and labeling per code — plan reviewers will check
• Commission and monitor: performance testing at startup and ongoing monitoring so underproduction gets caught, not discovered on the utility bill