A rooftop solar bill of materials lists every item the job needs, with a quantity counted or measured from the design and a price for each. It beats a single rupee-per-watt figure because the quote then changes when the design changes, and it shows the customer what they are paying for.
1. The main groups
- Solar modules: count from the layout, with DCR or non-DCR as the project needs.
- Inverter: size and number from the system capacity, single-phase or three-phase.
- Mounting structure: rails, rafters, columns, bracing, base plates, anchors and clamps, or aluminium rails for flush mounting.
- DC cables from each string to the inverter, and the AC cable down the building.
- Earthing and lightning protection.
- Protection and metering: breakers, surge protection, meters.
- Installation, transport, net-metering paperwork and commissioning.
2. Count from the drawing, do not guess
The cable length depends on where the inverter sits and where each string ends. The steel depends on the tilt, the row spacing and the height of each frame. If you draw the system in 3D, these can be measured instead of estimated, and a change in layout changes the quantities.
3. Price from a rate card you control
Keep a rate card with a price for each item: modules per watt, inverter by size, steel per kilogram, cable per metre, and labour. Update it when your vendor prices change, and let every quotation read from it. Prices move, so never hard-code them into a template.
4. DCR and the subsidy
For residential projects under PM Surya Ghar, the modules have to be domestic content (DCR) to qualify. The price of DCR modules is higher than non-DCR ones, so the bill of materials should switch cleanly between them, and the quotation should show the subsidy as its own line only when it applies. Confirm the current rules on the official portal.
5. Tax
Apply GST by item, with the right HSN code, and by place of supply. Some solar items and services are taxed at different rates, so a single blended rate is a shortcut that can be wrong. Check the current rates with your tax adviser.
6. Check the BOM before it becomes a quotation
- Is the module count the same as in the layout?
- Does the cable length make sense for this building?
- Is the structure steel in line with the wind and tilt?
- Are the margins what you expect after all items?
How RAYVO does this
In RAYVO, the bill of materials is built from the design: modules, strings, cable runs, structure, clamps, anchors, earthing and lightning protection are counted from the drawing and priced from a rate card you can edit. That total is the price used in the studio, the payback figures and the proposal. See the and .