A solar PV quotation process for commercial rooftop installers

Short answer: Take off modules and mounting from the roof layout, take inverters and protection from the single-line diagram, then measure DC and AC cabling between them. Check that the layout and the single-line diagram describe the same system before you price, and flag every mismatch with the sheet and revision it came from.

What goes into a commercial rooftop solar PV quotation?

For a commercial or industrial rooftop, the quotation usually follows a tender pack from a main contractor, a consultant or the building owner. It might include a roof layout, a single-line diagram, an equipment list, specifications and sometimes a BQ. Where there is no BQ, you price in your own format, but the items are much the same.

On top of these, most quotations carry preliminaries, access and lifting, testing and commissioning, and a clear list of exclusions.

How do you take off modules and mounting from the roof layout?

Count modules by array on the roof layout, not just the total in the notes. Arrays are often split around roof obstructions such as skylights, vents and existing plant, and a note saying "total modules" may not have been updated after the layout changed.

• Count each array separately and record the sheet and revision.
• Check the total against the system size on the single-line diagram, using the module rating in the equipment list.
• For mounting, record the roof type and fixing method, the number of rows, and the rail length if the BQ or your rate build-up uses it.
• Note walkways, safety lines and access provisions if they are shown. They are easy to leave out.

Whether the roof structure can take the load is normally assessed by others. If the tender doesn't say who does it, raise it as a query and state your assumption in the exclusions.

How do you check the inverter against the single-line diagram?

The single-line diagram shows how the system is meant to be connected: how many strings go to each inverter, what protection sits between them, and where the AC side connects to the building. Take inverters, combiner boxes, isolators and AC protection from it, then check that the layout supports it.

• Count inverters and their ratings, and match them to the equipment list.
• Check that the number of strings and modules per string adds up to the module count from the layout.
• Find where each inverter sits on the layout, because that drives the DC and AC cable lengths.

How do you measure DC and AC cabling?

DC cabling runs from each string to its inverter or combiner box. AC cabling runs from the inverters to the AC panel and on to the connection point in the building. Measure them separately, because they are different cables and usually different BQ items.

• Check the scale on each sheet against a known dimension before measuring.
• Measure string routes along the containment shown, not in a straight line.
• Add vertical drops from the roof to the inverter location where the inverters are not on the roof.
• Record your firm's allowance for terminations and loops as a rule on the line.
• Where a route is not drawn, mark the length as an assumption.

What if the roof layout and the single-line diagram don't agree?

This is common, especially where the layout was revised after the electrical design, or the other way round. Don't pick one quietly. Flag the mismatch, note which sheet and revision each figure came from, and decide with your estimator whether to price one option and state it, or raise a tender query.

How should you present the solar PV price?

If the consultant has issued a BQ, price in their layout and item numbering. If not, use a consistent format so the client can compare your quotation with others. Either way:

• List the system size and the main equipment so the client can see what is included.
• State assumptions clearly, especially for cable routes, roof access and lifting.
• List exclusions, such as structural assessment, roof repairs, or utility and authority applications if they are by others.
• Keep the sheet and revision behind each quantity, so a query after submission can be answered quickly.

Where do programmes like NEM come in?

Many rooftop projects in Malaysia are tied to a government programme, such as net energy metering (NEM) or the schemes that have followed it. The rules, quotas and application steps have changed over the years. Don't quote eligibility or savings from memory. Check the current guidelines from SEDA Malaysia and the utility, and make clear in your quotation who is responsible for the application.

Can AI help with solar PV takeoffs?

It can draft the counts and lengths, if it shows its working. UkurBQ sets up AI inside your own Claude or ChatGPT business account to draft the BQ from the tender drawings. It reads the roof layout and the single-line diagram together, shows the sheet and revision for each quantity, and flags mismatches like the ones above with a reason. Your estimator checks and signs off, then it is priced with your own rates.

FAQ

Should module quantity come from the layout or the system size?

Count from the layout and check against the system size. If they differ, flag it and confirm with the designer or raise a query.

Do we need a BQ to quote a rooftop solar job?

No. Many solar jobs are quoted in the installer's own format. The same takeoff steps apply, and recording the source of each quantity matters just as much.

How do we handle a revised roof layout during the tender?

List every line that came from the old sheet, re-check those against the new revision, and update the module, mounting and DC cable lines together, because they are linked.

Who should handle the NEM or scheme application?

It depends on the contract. State in the quotation whether it is included or by others, and check the current programme rules before promising anything.

Keep reading

• Waiting on supplier prices? How to send RFQs the day the tender lands
• AI takeoff from drawings: how to check every line before you price it
• What does AI estimating cost a Malaysian subcontractor?