Commercial Solar Due Diligence Checklist

Look for: NABCEP (North American Board of Certified Energy Practitioners) certifications for design and installation staff; licensed electrical contractor status in your state; general liability insurance ($2M+ per occurrence recommended for commercial work); workers' compensation coverage for all installers; completed commercial project references in your property type and system size range; manufacturer-authorized installer status for the panels and inverters proposed. Ask for proof of each, not just claims.

Production estimates should be generated using industry-standard simulation software (PVsyst, Aurora Solar, or HelioScope) with documented inputs including your specific GPS coordinates, shading analysis from site survey data (not satellite assumptions), panel degradation rates, inverter efficiency, and system losses. Ask the installer to provide the simulation report, not just the summary number. Compare the proposed annual production (kWh) against published NREL PVWatts estimates for your location as a sanity check. A reputable installer's numbers will be within 5-10% of PVWatts for a similar system configuration.

A complete commercial solar warranty package should include: (1) Panel manufacturer production warranty: 25 years at 80-85% output guaranteed; (2) Inverter manufacturer warranty: 10-15 years, with an extension option available; (3) Racking system warranty: 20-25 years; (4) EPC workmanship warranty: minimum 2-5 years on installation workmanship (roof penetrations, electrical connections); (5) Performance guarantee: some EPCs offer a production guarantee that compensates if the system underproduces against the modeled estimate. Verify that all warranties are with solvent, established companies — not just with the EPC that may not exist in 10 years.

Watch for: (1) Production guarantees based on satellite data without an actual site visit; (2) Contracts with automatic annual payment escalators in PPA or lease structures exceeding 3%; (3) Warranty terms from the installer, not the manufacturer; (4) Unrealistic payback claims (under 3 years for purchased systems); (5) Installers who cannot provide commercial project references in your property type; (6) Equipment from manufacturers without established US distribution and warranty fulfillment; (7) Contract terms that prevent you from switching energy providers or refinancing your property; (8) Vague or missing descriptions of system monitoring, maintenance responsibilities, and end-of-life decommissioning.

Work with a tax attorney or CPA experienced in Section 48E tax credits independently of the installer. Key ITC qualification factors to verify: the system must be placed in service (energized and connected) by December 31, 2027; the equipment must meet FEOC compliance requirements for projects beginning construction after July 4, 2025; the ITC basis calculation must correctly account for any grants or rebates received; and your ownership structure must be eligible for ITC claiming (certain partnership and passthrough structures have specific rules). Do not rely solely on the installer's representation of tax credit eligibility.

Yes, and it is standard practice. We recommend obtaining 2-3 proposals from different EPCs before committing. Compare: system design and production modeling methodology, equipment specifications and manufacturer warranty terms, financing structures and net present value calculations, interconnection timeline and utility experience, project references and completed work samples, and total cost and net cost after incentives. Our platform is designed to help you compare proposals from vetted installers on a common basis. Many of the variables that look similar on proposals have significant quality differences underneath.