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What is the difference between mono and poly solar panels?
Below are pictures of two solar panels:
A couple of things stand out right away with their appearance. This is due to how solar cells, or the individual squares are made.
The monocrystalline solar panel is a consistent black or very very dark blue color. It is cut into wafers from a conical silicon ingot that is grown in a lab. To make the ingot the silicon rocks are melted at 2,500 °F (1371°C), and then a seed crystal is lowered into the melted slush, and slowly pulled up while rotating. Because of the round shape, there is a lot of material wasted as they cut it into the required square shape. That is why they usually have rounded corners, to help minimize the waste.
Polycrystalline cells are made a different way. They load about 1300 pounds of silicon rocks into a 3 foot (0.9144M) by 3 foot (0.9144M) quartz mold to create a square shape, and then load it into a 2,500 °F (1371°C) furnace. It takes 20 hours to melt, and about 3 days to cool down. Like a piece of particle board, it looks like it is made up of multiple pieces of silicon pressed together. That is actually caused from when the melted silicon cools and hardens, it crystallizes. When it is sawn into the wafers, there is much less wasted material from the square ingot than from the round monocrystalline ingot, and is a less expensive manufacturing process.
Due to the higher cost of manufacturing, monocrystalline panels tend to be a little more expensive than polycrystalline panels. Although efficiencies in manufacturing processes are really reducing the cost difference. Monocrystalline panels look different and cost a little bit more than polycrystalline. But the big question is, is it worth worrying about the difference? To help answer that, let’s talk about performance differences. Monocrystalline solar panels tend to be more efficient than polycrystalline solar panels. Let’s say on average about 17.5% vs.15.5% module efficiency. So they are 2% more efficient. What does that really mean? It means that you can have slightly more power in the same amount of space with monocrystalline than polycrystalline.
Let’s look at the specifications of two panels from Canadian Solar. They are both the same size, 1960mm x 992mm.
Both panels output 325 watts. Both panels have a 16.72% efficiency. If I were to build a 3250W system, I will require 10 panels whether mono or poly. The cost of the solar panels may be less for polycrystalline.
One performance difference is how they react to temperature. Monocrystalline panels handle the heat slightly better than polycrystalline. How slight is slight? Comparing the temperature coefficient of the two types shows us that monocrystalline short circuit current drops 0.053% for every degree Celsius over standard test conditions of 25 degrees Celsius, or 77 degrees Fahrenheit. So if it is 20 degrees hotter on the roof than under test conditions, the monocrystalline solar panel can lose .08 amps out of a rated 7.46 amps. For the polycrystalline, it also loses 0.053%. That equals losing .08 amps also out of a rated 7.57 amps. So the difference is almost negligible for the two panels in the example. In extreme desert conditions, the difference may be big enough to matter, but for most residential environments, the difference will probably be nil.
Finally, monocrystalline panels tend to behave a little better in less than perfect light conditions. No solar panel, regardless of their type, performs well in the shade. But, if you have slight shading issues, or tend to have hazy skies, monocrystalline panels may perform a little better. However, with the availability of microinverters and DC optimizers maximizing each panel in the solar array, the difference may not be noticeable. Or if you’ve located your solar array so that there are no shading issues, there’s no difference at all.
So as you can see, the differences between monocrystalline and polycrystalline panels is not as dramatic as it once was. Advances in technology have made them practically interchangeable. So your choice of which crystalline technology to use may simply come down to color preference, space constraints or money.