Mono PERC vs TOPCon Modules for a C&I Plant: Yield, Price and Warranty

For a C&I plant, TOPCon (n-type) modules generally give more output per square metre and a slower degradation curve than mono PERC (p-type), usually at a higher module price per watt. PERC remains a valid, often cheaper choice where roof area is not tight and the horizon is shorter. The deciding numbers are on the datasheet: efficiency, degradation guarantee, temperature coefficient and warranty.

How do the two technologies compare on the datasheet?

The table sets out the fields to compare. The typical figures are those in our TOPCon explainer; they describe module classes, not any particular product, so replace them with the datasheet of the model you are quoted.

Read the table as a list of questions, not a verdict. Two modules of the same technology can differ more than two technologies do, and the datasheet of the actual model governs.

When does TOPCon pay for itself, and when is PERC enough?

• Roof area is the constraint. A higher-efficiency module puts more kilowatts on a fixed roof. If your roof limits the plant below what your load could use, efficiency has a direct value.
• A long hold. Output in year 20 depends on the degradation curve. If you will own the plant for its full life, the slower curve is worth pricing; if you plan to sell the building within a few years, it is worth less to you.
• A hot roof. A smaller temperature loss matters most in the months when the module runs hottest and your demand is highest. Compare the datasheet figures; do not rely on the technology label.
• Roof area is not tight and the budget is. A PERC bid that meets the specification and carries a clean warranty can be the better purchase if the price gap is real and your horizon is moderate.
• Ground-mount or bifacial design. If you are buying bifacial for the rear-side gain, compare bifacial with bifacial; the technology question and the bifacial question are separate.

What do the standards and the ALMM rules say?

Neither technology is exempt from the same basics. SECI's rooftop tender specification, as one published example, requires modules to qualify to IEC 61215 or its BIS equivalent IS 14286 and to IEC 61730 for safety, with IEC 61701 for highly corrosive atmospheres; ask each bidder for the test reports of the exact model.

The ALMM rules follow the route, not the cell type. Under MNRE's memorandum of 4 August 2026, net-metering and open-access projects need modules on List-I, and cells on List-II if the plant is commissioned after 31 December 2026, while a private plant behind the meter used solely for captive consumption is outside both lists. If your commissioning date falls after 31 December 2026 on a net-metered or open-access route, the cell manufacturer must be on List-II, whatever the technology; ask each bidder which cell maker it uses and check it against the list on the supply date, since MNRE revises the lists. Our ALMM guide and bankability note go further.

What should the warranty and supply terms look like?

A module has two warranties. The product warranty covers defects in materials and workmanship for a stated number of years. The performance warranty guarantees a minimum output, usually as a year-one floor followed by a yearly step-down to a year-25 floor, and it is the clause that carries the technology difference. Read whether the performance line is linear or stepped, what the year-one figure is, and what remedy the maker offers: replacement, repair or a payment. A warranty is only as good as the entity behind it, so ask who in India you would make a claim against, and whether that entity is the manufacturer, a subsidiary or only a distributor. Also write the exact model, the cell maker and the delivery period into the purchase order, because a model that is listed on the day of order may change before dispatch.

How do you compare two bids fairly?

1. Fix the plant size in kWp DC and compare module count and wattage, not price per module.
2. Ask for the warranty text: product warranty period, the year-one and annual degradation guarantee, and the year-25 output floor.
3. Ask for the temperature coefficient and the model's test reports.
4. Check the exact model on ALMM List-I and the cell maker on List-II where it applies.
5. Price both on the same wattage, structure and scope, then compare on expected output over the period you will hold the plant, not only on first cost.

A small illustration of why the curve matters, using round numbers and not any maker's datasheet: each extra 0.1 percentage point of annual degradation leaves about 2.4 percent less output in year 25, since 0.999 raised to the 24th power is about 0.976. On a 1 MW plant making about 14.4 lakh units in its first year, which is the figure on our 1 MW page, 2.4 percent is about 34,000 units in year 25 and roughly half that on average over the life. Whether that outweighs the price gap depends on your tariff and your horizon, so run both bids through the solar calculator. Our guide to comparing solar EPC quotes lists the other lines.

Module cost is one line in the turnkey band we publish, ₹24,000–32,000 per kW excluding GST, and we do not publish a separate premium for TOPCon over PERC.

How Secured Engineers helps

We design C&I solar in-house and file DISCOM net-metering, Fire NOC and CEIG applications in-house, with MEPF and solar under one contract. Our solar quotations state module technology, ALMM status and the manufacturer's warranted degradation curve, so that bids compare on output rather than a day-one wattage. We work from offices in Noida (Delhi NCR) and Ludhiana, with 535+ projects across 18+ states and 89.77% repeat clients. Our solar PV modules page covers how we specify them.

If you hold two quotations with different module technologies, send them and we will lay them side by side on warranty, ALMM status and expected output. See our solar EPC service, message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.