How to choose a solar installer: the questions vetted vendors should answer

Why this decision outweighs every other

Panels are commodities within a quality tier. Inverters are catalogue items. The engineering that turns them into twenty-five years of reliable generation — structure, wiring, earthing, waterproof penetrations, commissioning, and the phone that answers in year six — comes from the installer. Choose well and the system is boring in the best way. Choose badly and you inherit an underperforming array with orphaned warranties, welded to your roof.

India's rooftop boom has produced thousands of installers spanning the full spectrum from excellent engineering firms to short-lived operations that will not exist when your inverter faults. From brochures, they are indistinguishable: everyone claims a decade of experience, everyone promises 25-year performance, everyone photographs the same blue rectangles. The information that actually separates them has to be collected deliberately. Here is how.

First, the mandatory floor: empanelment

If you want the PM Surya Ghar subsidy, your installer must be empanelled with your DISCOM — the portal lists them. This is non-negotiable and also nearly useless as a quality filter: empanelment verifies registration, basic credentials and scheme compliance, not workmanship or service. Treat it as the entry gate to your shortlist, never as the shortlist itself.

The five-point vetting framework

1. Verifiable installed base

Claims are free; addresses are evidence. Ask for specific installed sites — ideally in your area, of your system's approximate size — and permission to speak to those customers. A vendor with a real installed base produces references without friction. Questions worth asking a reference: Did the project finish on schedule? Did the quoted components arrive? What happened the first time something needed service?

2. Component sourcing and paper

Ask exactly which module brand and model, which inverter brand and model, and which mounting structure (material, coating, gauge) the quote includes — and ask to see the warranty documents for each. Two red flags: quotes that name only a tier ("Tier-1 panels") without a brand and model, and reluctance to put component specifics in the contract. What is not written down is what gets substituted.

3. Workmanship standards

The craft is in the details that don't photograph well: earthing done to standard, DC and AC protections properly rated, cable runs protected from UV and abrasion, roof penetrations sealed so waterproofing survives, structures anchored for wind load. You can assess this indirectly — ask how they do each of these, and watch whether the answer is specific — and directly, by looking at one of their older installations rather than last month's.

4. After-sales reality

The question that predicts your year-six experience: "Tell me about a service call from a system you installed three or more years ago." Firms with real service operations have boring, specific answers — ticket systems, response norms, spares. Firms without them change the subject to their installation speed. Also check simple longevity signals: how long has the firm existed under this name and GST registration? A 25-year warranty from a 2-year-old company is a sentence worth thinking about.

5. Commercial hygiene

Payment milestones tied to delivery and commissioning (never large advances against nothing), named delivery and commissioning dates, and the installer's obligations through DISCOM inspection — including fixing punch-list items and attending re-inspection — written into the contract. Good vendors accept these terms readily; the resistance itself is information.

Making three quotes comparable

The standard failure mode of solar shopping: three vendors, three different system designs, three incomparable prices — and a decision made on gut feeling dressed as analysis.

The fix is procedural. Fix the specification first — capacity, module class, inverter class, mounting, protections, warranty definitions, commissioning scope (ideally from an independent site survey and design) — and have every vendor quote that. Now the comparison table means something:

With a fixed spec, an outlier price demands an explanation. Sometimes it's legible and fine — leaner overheads, a consciously chosen component tier. When it isn't explainable, it's a corner you'll discover after commissioning.

Warranty literacy in three paragraphs

Panel product warranty (commonly 10–12 years) covers manufacturing defects — delamination, junction-box failures, hotspots. Panel performance warranty (commonly 25 years) guarantees output degradation stays within a stated curve, typically landing around 80–90% of rated output at year 25. They are different documents with different claims processes.

Inverter warranty commonly runs 5–10 years, often extendable at purchase — usually worth pricing, since the inverter is the component most likely to need attention within the system's life.

Critically: panel and inverter warranties are usually manufacturer warranties, which survive even if your installer's firm doesn't. That only helps if you hold the paper — serial numbers, warranty certificates, purchase and commissioning records — from day one. Archive them the week of installation.

The decision, honestly framed

After vetting and a like-for-like comparison, most buyers face a legible choice: a somewhat cheaper bid from a thinner operation versus a somewhat costlier one from a firm with demonstrable service depth. There is no universal right answer — but there is a right frame: you are not buying a gadget, you are choosing a counterparty for a decades-long relationship your roof can't easily exit. Priced per year of system life, the premium for a firm that will still answer the phone is usually the cheapest insurance in the project.

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This framework is our installer vetting and quote comparison service in written form. We run it for clients with no installer commissions of any kind — the recommendation is one nobody paid for. Names on our vetted list are earned on these criteria and lost when service slips.