About the Structure Material BOQ
The mounting-structure Bill of Quantities (BOQ) estimates the steel or aluminium needed for the module mounting system, driven by the number of modules, the array layout, and the site's wind zone.
How to calculate it
- 1Fix the array configuration (portrait/landscape, modules per table, tilt).
- 2Determine the design wind load for the site's wind zone (IS 875 Part 3).
- 3Size the purlins, rafters, columns and bracing to carry dead + wind load within allowable stress (IS 800).
- 4Total the member lengths and convert to weight — a hot-dip galvanised steel rooftop structure is typically ~40–60 kg per kWp.
Worked example
A 100 kWp rooftop array at roughly 50 kg/kWp needs about 5 tonnes of galvanised steel, plus fasteners and base plates — refined by the exact wind zone and roof type.
What you can calculate
- Channel / purlin kg
- Clamp count
- Nut bolt count
- Wastage factor
Standards & references
Frequently asked questions
How much steel does a solar mounting structure need?
A galvanised-steel rooftop mounting structure typically uses about 40–60 kg of steel per kWp; ground-mount structures are heavier. The exact figure depends on the wind zone, span, tilt, and whether steel or aluminium is used.
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