Monocrystalline vs polycrystalline solar panels, from the datasheets

The names describe the silicon. A monocrystalline cell is sliced from one crystal and a polycrystalline cell is cast from many, and that one difference shows up in three figures on a datasheet: how much a panel makes from its glass, how much it loses on a hot roof, and how many of them a system takes.

This page reads those figures from one current mono datasheet and one poly datasheet and works the comparison from them. It names no brand as a recommendation. The point is how to read the sheet you are handed.

How each one is made, and why it matters

Both start as the same purified silicon. For a monocrystalline cell the silicon is melted and a single cylindrical crystal is drawn out of it, cooled, and sawn into thin wafers, which is why mono cells have clipped corners and an even dark colour. For a polycrystalline cell the molten silicon is cast into a block and allowed to set as many small crystals, then sawn, which gives the speckled blue look. The boundaries between those crystals get in the way of the electrons, so a poly cell turns a little less of the light into current.

The US Department of Energy’s solar office describes the drawn-crystal process as the one most modules are now made by, with monocrystalline silicon at 96 percent of global shipments in 2022, and industrially made modules reaching 20 to 22 percent efficiency. Within mono, the design has moved on too: the PERC cell overtook the older design around 2018, and the industry is now moving to n-type cells such as TOPCon, which is what the mono datasheet below is.

One datasheet of each, side by side

The mono panel is the JinkoSolar Tiger Neo JKM580-605N-72HL4-(V), a current module. The poly panel is the Canadian Solar MaxPower CS6U-325|330|335P, an older product line, because that is the generation of module poly is sold as. The last three rows are worked out from the rows above them, at each panel’s lowest rating.

From the datasheet	Mono	Poly
Cell	Monocrystalline, N-type TOPCon	Polycrystalline, 72 six-inch cells
Rated output per panel	580 to 605 W	325 to 335 W
Module efficiency	22.45 to 23.42 percent	16.72 to 17.23 percent
Watts per square metre of glass	225 W/m²	167 W/m²
Loss per degree above 25 °C	-0.29 percent	-0.40 percent
Panels for a 5 kW array	9	16
Glass for a 5 kW array	23.2 m²	31.1 m²

Watts per square metre is the lowest rating over the module’s face: 2278 by 1134 mm for the mono panel and 1960 by 992 mm for the poly one. The 5 kW rows divide 5,000 W by one panel’s rating and round up.

What a hot roof does to each

Every datasheet figure is measured at a cell temperature of 25 °C. A panel on a roof here at midday is well above that, and each type loses output for every degree over. The poly sheet prints a nominal operating temperature of 43 °C in mild test conditions, and a roof in April is not mild.

Take a cell temperature of 60 °C as an illustration, 35 degrees above the test. The mono panel’s coefficient of -0.29 percent per degree gives up about 10.1 percent of its rated output. The poly panel’s -0.40 gives up about 14.0 percent. The gap is not dramatic on one afternoon. Over a year of afternoons it is one of the reasons the industry moved.

The 60 °C figure is a worked illustration, not a measurement of any roof. Dust and heat together are what the 0.8 performance ratio on the solar panel calculator allows for. Why a cell turns only part of the light into electricity is on what is solar energy.

Which suits a Philippine roof

Monocrystalline, for two reasons that have nothing to do with fashion. The first is heat, above. The second is space. A subdivision house here usually has one roof face that gets the midday sun, and the mono panel on this page makes about 225 W from each square metre of it against 167 for the poly one. The 5 kW array takes 9 mono panels on 23.2 m² of glass, or 16 poly panels on 31.1 m², and the roof has to find room around whichever it is. What each roof type can take.

What the two types share matters as much. Both get dirty in the same dry season dust and both are cleaned the same way. Both lose output slowly over the years, which the lifespan page reads from a field review and a warranty sheet. And both are only as good as the mounting under them and the inverter behind them.

If a quotation offers polycrystalline panels, ask for the datasheet and read three lines off it: module efficiency, temperature coefficient of Pmax, and the power warranty. Then set them beside a mono sheet the way this page does.