Ask an installer what went wrong on their worst job, and you rarely hear about a faulty product.
You hear about the inverter that arrived three weeks after the scaffolding went up. Or the customer whose subsidy claim was rejected because a model number on a certificate did not match the one on the panel. Or the module that failed in month four, with the supplier pointing at the manufacturer and the manufacturer pointing back.
None of those are quality problems. They are supply problems, and they cost far more than the few rupees per watt most installers spend their time negotiating over.
So what should you actually check before you place a first order with a new supply partner?
What a supply partner does beyond selling you boxes
The price list is the easiest part to compare and the least useful. Every serious distributor buys from the same manufacturers at similar terms, so the gap between two quotes is usually thin.
What varies enormously is everything around the box.
- Whether the stock exists when they say it does, and how fast it reaches your site.
- What paperwork comes with it, and whether that paperwork survives contact with a DISCOM inspection.
- Who handles a warranty claim when a unit fails in year two.
- What credit you get determines how many jobs you can run at once.
- Who picks up the phone when a system will not commission at four in the afternoon.
Judge a supplier on those five. The price difference between a good one and a cheap one usually disappears on the first delayed project.
Start with the paperwork, not the price
This is the part that catches most installers, and it has become sharper in the last year.
For any project claiming a subsidy or drawing on government funding, the equipment must appear on the right approved list. Solar modules are covered by the Approved List of Models and Manufacturers, maintained by the Ministry of New and Renewable Energy. List-I covers finished modules. If a module model is not on it, the subsidy does not get released, however good the installation is.
From June 2026, that requirement extended down the supply chain. Cells used inside those modules now need to come from manufacturers approved under a second list, with a further stage covering wafers due later. In practice, this means a module that qualified last year may not qualify today, and the answer depends on the exact model rather than the brand.
On inverters, be careful what you read. Trade coverage disagrees about whether inverters fall under the same approved list. Two things are not in dispute. Grid-connected solar inverters sold in India require BIS certification, and your DISCOM has its own empanelment requirements for the models it accepts. Treat anything you read on a blog, including this one, as a prompt to check, not as an answer.
Which leads to the only reliable method:
Verify the exact model number yourself, on the MNRE portal, before you buy. Not the brand, and not the series. The model number as printed on the label, matched against the current list. A different model from the same manufacturer is not interchangeable.
Then ask your supplier for the documentation in writing, before the order rather than after it:
- Current approved-list status for the exact model you are buying
- BIS certification for the inverter model
- Warranty certificates in the end customer’s name where the scheme requires it
- Test reports and datasheets matching the delivered model
- Serial numbers recorded at dispatch, so what arrives can be matched to what was invoiced.
A supplier who can produce that pack within a day is telling you something useful about how they operate. One who takes a week, or sends a datasheet for a similar model, is telling you something too.
Who handles the warranty when something fails?
Most installers do not ask this until they need the answer, which is the worst possible time.
There are two models, and they behave very differently.
The supplier handles the claim
You raise it with them; they deal with the manufacturer, and a replacement reaches you. Your relationship stays with one company that wants your repeat business.
You deal with the manufacturer directly
The supplier passes you a contact and steps back. You are now a small customer of a large company, without the leverage your distributor has.
The second is not automatically bad, particularly with manufacturers who run a good service network in India. It is bad when you find out about it during a claim.
Four questions worth asking before you commit:
- Who do I raise a claim with, you or the manufacturer?
- What is the typical turnaround from claim to replacement?
- Do you hold buffer stock for replacements, or does the customer wait for the manufacturer’s cycle?
- Who pays for the site visit and the labour to swap the unit?
That last one causes more arguments than any other. Product warranties rarely cover the cost of sending someone back to a roof.
Can they actually supply, when they say they can?
Quoted lead times are optimistic in every industry. The question is by how much, and whether the supplier tells you early when a date is going to slip.
Some things worth establishing:
Where the stock physically sits
A supplier holding inventory in a warehouse near you behaves differently from one drop-shipping from a manufacturer’s plant. It shows up in lead times and in how quickly a replacement reaches you.
What happens to a part-shipped order?
If eight of your ten inverters arrive, do the other two follow next week or next month, and does anyone tell you without being asked?
How they handle a model being discontinued mid-project
Product ranges change. A supplier who calls you before substituting a model is worth more than one who ships the nearest equivalent and lets you discover it on site.
Whether they will commit a date in writing
Not a promise of speed, just a date they are willing to put on paper. Suppliers who will not do this usually have a reason.
Credit terms decide how many jobs you can run
For a small installer, this matters more than the unit price, and it is often negotiable in ways the price is not.
Payment against delivery ties up your cash until the customer pays, and customers on subsidy schemes pay late by design, since the subsidy arrives after commissioning and inspection. Thirty days of credit can be the difference between running two jobs at once and running four.
Ask what terms become available after a few clean transactions, not only what is on offer today. A supplier who will grow the relationship is more useful than one offering a slightly better rate now.
Technical support, tested before you need it
Every supplier claims technical support. The claim is easy to test.
Before placing a first order, send a real question. A configuration query, a compatibility question about mixing an inverter with a particular module string, something you actually need to know.
The reply tells you three things. How quickly they respond, whether the person answering understands the product, and whether you get a straight answer or a link to a datasheet.
Ask specifically whether they support you at commissioning. That is when problems surface and when a supplier who takes the call is worth a great deal.
The questions to ask before your first order
A short list to work through, in this order.
- Is the exact model on the current approved list, and can you send proof today?
- Which documents come with the shipment, and in whose name?
- Who do I raise a warranty claim with, and how long does it usually take?
- Where does the stock sit, and what date will you commit to in writing?
- What credit terms are available now, and what could they become?
- Who do I call at four in the afternoon when a system will not commission?
Six answers, and you will know more than a price comparison could ever tell you.
Frequently asked questions
What is the difference between a solar distributor and a manufacturer?
A manufacturer builds the product. A distributor buys from several manufacturers, holds stock, and supplies installers and EPC companies. Buying through a distributor usually means faster availability, one relationship covering several brands, and credit terms a manufacturer may not offer on small volumes.
Do I need to check the ALMM listing for every project?
For any project claiming a subsidy or using government funding, yes, and check the exact model, not the brand. For a purely private commercial installation with no subsidy involved, the approved-list requirement does not apply, though BIS certification and your DISCOM’s connection requirements still do.
What documents should come with a solar equipment order?
At minimum, an invoice carrying model and serial numbers, warranty certificates, BIS certification for the inverter, and datasheets and test reports matching the delivered model. Add current approved-list evidence where a subsidy is involved. Ask for the pack before you order, not after delivery.
How do I check if a supplier is reliable before ordering?
Place a small first order and watch what happens. Whether the date holds, whether the paperwork is complete, whether anyone contacts you when something changes. One small order teaches you more than any amount of reference checking.
Should I buy from the cheapest supplier?
The unit price gap between established suppliers is usually narrow. The cost of a delayed delivery, a rejected subsidy claim or a slow warranty replacement is not. Compare on documentation, availability and warranty handling first, then let price decide between the ones that pass.
Where to start
Pick the next job you have coming and work through the six questions above with whoever you are planning to buy from. It takes one phone call and one email.
If the answers come back quickly and in writing, you have found something worth keeping. If they do not, you have learned that in a small order instead of a large one.
GP Eco Solutions began as a distribution business. We work with installers, EPC companies, and businesses across India, supplying solar inverters and storage, HT and LT panels, and SCADA monitoring.
Our distribution team can help with finding the right fit for a project, system compatibility, and after-sales support. Tell us what you have coming up, and we will talk through availability.