Monocrystalline vs Polycrystalline vs Bifacial: Which Panel Belongs on Your Roof?

Almost every rooftop quotation you receive mentions mono PERC, TOPCon or bifacial modules. The labels matter less than what they do to your generation, your roof area and your bill, so here is the plain version.

Polycrystalline: the old workhorse

Poly modules are cast from multiple silicon crystals and show the familiar blue speckled pattern. They are cheap and tolerant, but efficiency sits around 15 to 17 per cent. Most manufacturers have moved on and spares are getting harder to source, so we rarely propose poly for a new rooftop today.

Monocrystalline PERC and TOPCon: the current default

Mono modules are cut from a single silicon ingot, look uniformly dark and convert 20 to 22 per cent of incident light. For the same 100 square feet you get noticeably more kilowatts, which matters when roof space is the binding constraint — and in most Indian homes it is.

TOPCon is the newer cell architecture inside the mono family. It adds roughly a percentage point of efficiency and degrades a little slower, and the price gap over standard mono PERC has narrowed enough that it is usually worth paying.

Bifacial: generation from both faces

A bifacial module has glass on the rear as well, so it also captures light reflected off the roof surface. On a light-coloured terrace or an elevated structure with clear space underneath, the rear face can add 5 to 15 per cent. Flush-mounted on a dark roof with no air gap that gain nearly disappears, so bifacial only pays for itself when the structure is designed for it.

What actually decides the choice

• Shadow-free roof area: tight roofs favour the highest efficiency module you can afford
• Structure height: elevated or ground-mounted arrays justify bifacial, low flush mounts do not
• Budget against payback: a cheaper module that fills the whole roof often beats a premium module you can only afford for half of it
• Bankability: a 25-year performance warranty is only as good as the company standing behind it

Numbers to compare across quotations

Ask for module wattage, efficiency, temperature coefficient (lower is better in Punjab summers), annual degradation and both warranties — product and performance. Two quotations at the same rupees per watt can differ by 10 per cent in lifetime output on these numbers alone.

Our usual recommendation

For most homes in Punjab, Chandigarh and Haryana we specify tier-1 mono PERC or TOPCon modules, and switch to bifacial when the roof allows an elevated structure or the client wants maximum generation from limited area. Send us a photo of your roof and we will tell you which of the three suits it.