How to select a solar EPC contractor — modules, structure, approvals and the performance guarantee
A solar plant is bought once and judged for twenty-five years. The contractor's sizing basis, the structure on your roof, who files the net-metering application, and whether the performance guarantee is measurable — these matter more than the rupees per kilowatt, and they are what this checklist tests.
Last reviewed · Reviewed for checklist content, linked standards Authority names, portals, fees and timelines change with state notifications; confirm the live position with the authority before relying on it.
What to check
- Plants of your type and size in operation, with generation data the owner will share
- Who files DISCOM net-metering and CEIG applications — the contractor as applicant, or you
- Structural engineering — a wind-load design for your roof type, stamped by an engineer
- Module and inverter supply chain — tier-1 makes, ALMM listing where the scheme requires it
- Monitoring and O&M capability after commissioning
Documents to request
- Shadow analysis and yield estimate for your site, with the assumptions stated
- Module datasheet with IEC 61215/61730 certificates and, where required, the ALMM list reference
- Inverter datasheet with IEC 62109 certification and the grid-protection settings
- Structural design and a sample stability certificate
- Net-metering approval letters from two recent projects (client details may be redacted)
- A sample monthly performance report from an O&M contract
Technical questions to ask
- What capacity does our consumption and sanctioned load support, and how does the proposal compare with the roof-limited capacity?
- What is the yield basis — irradiance source, losses assumed, performance ratio guaranteed?
- Ballasted, anchored or clamped structure, and what does the roof have to carry?
- String or central inverters, and why, for our roof orientations and shading?
- How will the plant tie into the LT panel, and what protection does the DISCOM require?
- What monitoring will we have, and at what level — plant, inverter or string?
Commercial questions to ask
- Is the price per kWp on a stated module wattage and count, or on a round number?
- What is included: structure, cabling, protection, metering, monitoring, approvals, structural certificate?
- Is the performance guarantee a generation or performance-ratio figure with a remedy, or a brochure sentence?
- What are the module, inverter and workmanship warranties, and who holds them?
- What does the O&M contract cover, at what cost, for how long?
Hidden scope gaps to look for
- Net-metering application "by client"
- Structural strengthening of an old roof excluded, discovered at installation
- A plant sized to the roof rather than to consumption, exporting at a low tariff
- Sanctioned load ignored, then the net-metering capacity capped
- Monitoring hardware excluded
- Non-ALMM modules on a project that needs ALMM
Commissioning documentation to insist on
- Module serial-number schedule mapped to strings, with flash-test data
- String open-circuit voltage and polarity test record
- Inverter protection settings as configured, matching the DISCOM's requirements
- Earthing test record for the array
- Structural stability certificate
- DISCOM joint-inspection report, net-metering approval and meter details
- Monitoring access and the first generation report
Warranty and AMC terms to review
- Module performance warranty (linear degradation) and product warranty, assigned to the owner
- Inverter warranty term and extension options
- Workmanship warranty on structure and cabling
- O&M: cleaning frequency for the site's soiling, inverter servicing, string monitoring, performance-ratio reporting, response times
Safety and compliance issues that matter
- IEC 61215/61730 modules; IEC 62109 inverters; ALMM where required
- CEIG approval for plants connected at HT or above the state's threshold
- DISCOM connection standard for protection and metering
- Roof-edge protection and fall-arrest during installation; array earthing and surge protection
How Secured Engineers can help
Secured Engineers Pvt. Ltd. sizes to consumption and sanctioned load, designs the structure for the roof and the wind load, files net-metering and CEIG as the applicant, and reports performance ratio under its O&M contracts. The long-form guide to choosing a solar EPC company goes deeper into the evaluation criteria; the solar calculator frames the commercial case before a survey.