Solar-Ready Roofing Calculator

This calculator checks whether a roof can structurally support a planned solar panel installation, converting panel count and weight into a distributed load and comparing it against the Spare Roof Dead-Load Capacity you enter -- the margin the existing framing has beyond the roofing it already carries, which comes from a structural review or the original design documents rather than from anything the calculator can infer. Panel Weight is what actually determines Load (PSF) -- the number of panels you plan to install cancels out of that calculation entirely, since both the total weight and the total panel area scale together with panel count, leaving only the per-panel weight-to-area ratio in the result. Number of Panels does still matter for Total Load in pounds and for Roof Coverage percentage, both of which scale up directly as you add more panels. Roof Age doesn't affect the structural load calculation at all; it only produces the separate Roof Life Remaining figure, assuming a 25-year total roof lifespan.

Roof Area affects Roof Coverage inversely -- the same panel array covers a smaller percentage of a larger roof. If Load (PSF) comes out above your Spare Roof Dead-Load Capacity, the calculator flags Reinforcement Needed and reports Structurally Adequate as No. The 5 psf default is a typical residential margin, not a code value: solar arrays are normally budgeted to add 2-4 psf, so a roof with less than that to spare fails the check while a purpose-built or recently reframed roof may have far more. Get the real number from a structural engineer before relying on this verdict.