Ask for exact module and inverter models, structure specification, protections, cable, monitoring, warranty responsibility and exclusions. Two systems with the same kW rating can differ substantially in equipment and installation quality.
Use milestone payments
Consider linking payments to survey/design, material delivery, installation, inspection or commissioning and final handover. The exact structure depends on the vendor contract, but full advance removes leverage if work is delayed.
Check generation assumptions
A vendor may quote annual units using ideal conditions. Ask what shade, orientation, system losses and downtime are assumed. Compare the estimate with your daytime consumption and current export rules.
Keep subsidy separate from vendor payment
Do not allow a vendor to treat the expected government benefit as guaranteed cash owed by a fixed date unless the official process supports that. You are buying the system; subsidy is a separate government workflow.
Handover checklist
Collect invoices, serial numbers, warranties, commissioning/test records, monitoring login, shutdown procedure and portal/DISCOM documents. If subsidy is delayed later, this evidence helps prove that installation stages were completed.
The best project is one that makes financial sense from electricity savings and system quality, with the subsidy improving the outcome rather than rescuing a poor quote.