Most solar modules used today are either polycrystalline or monocrystalline, otherwise known as mono and poly. So what is the difference between polycrystalline and monocrystalline?
For the sake of brevity, the difference between the two is that monocrystalline is composed of a single crystal of silicon, while polycrystalline is composed of many crystals.
These two kinds of crystalline silicon cells are both commonly used today in cells of photovoltaic modules. These cells are made from silicon, a semiconductor material derived from quartzite. Silicon is one of the most abundant natural resources on the planet.
Monocrystalline, which is also called single crystalline, is the older of the two technologies and has been around since 1955. Monocrystalline is still used to manufacture photovoltaic cells today and is arguably the most efficient material available.
Extensive filtration is required to purify the silicon so it can be used for monocrystalline solar cells. To create a monocrystalline cell, the Czochralski method is employed. A single monocrystalline silicon seed crystal is slowly pulled from the high-heat molten silicon. As it’s drawn upwards, the silicon cools and solidifies as a single ingot. This cylindrical ingot is then sliced into thin pieces that are then cut into the cell shapes you see on a monocrystalline solar panel.
Though monocrystalline cells function well in low-light conditions, elevated heat can cause the conversion rate to decrease. In lab conditions, these kind of solar cells are more efficient than their polycrystalline cousins. Monocrystalline cells have a long life and are very durable. Monocrystalline technology is still more expensive than other solar technologies, including polycrystalline.
Polycrystalline, which is also called multicrystalline, came about in 1981. Polycrystalline cells, which are composed of multiple silicon crystals, is a cheaper way to manufacture solar modules. Put simply, these cells are easier for a factory to produce, so they are less expensive.
Polycrystalline cells are made by several methods, but most commonly with a cast of molten silicon. When these cells are being created, they cool faster, creating smaller crystals. Polycrystalline cells are easily identified by their fragmented texture that somewhat resembles a granite countertop or shattered glass. Just remember that “poly” means “many,” so it has many crystals.
Though monocrystalline is still more efficient at energy conversion in lab settings, polycrystalline is quickly catching up. Because of this, polycrystalline panels are generally slightly bigger than monocrystalline panels. As technology progresses, the gap between mono and poly continues to shrink. Polycrystalline cells are known to function better than monocrystalline under high-heat circumstances. Though many would automatically assume that monocrystalline cells are better because they are made from single crystals of silicon, it doesn’t necessarily mean a better panel.
So… Mono or Poly?
The short answer is that is is difficult to say one way or the other because there are a multitude of factors you should consider before you purchase your solar panels. If you’re trying to maximize the space you have available on your roof, monocrystalline might be the right choice for you. But maybe not. Let’s try to break this down a bit.
Nameplate ratings are used by manufacturers to give you an idea of how much energy a module will produce. The problem with this is that their lab settings, or Standard Test Conditions (STC), do not necessarily reflect the real-life conditions that a solar module will be subjected to during its use. The module will function differently in a lab with a perfect 78 degrees Fahrenheit than it will on a smoldering summer afternoon, or a cold winter morning.
PVUSA Test Conditions, or PTC, are used by the California Energy Commission to get a more accurate idea of how modules actually function in real-life conditions. PTC scores are often referred to as CEC ratings. CEC ratings can provide a more accurate expectation of how a solar module will perform under real-world conditions, rather than a sterile, consistent laboratory. You’ll be surprised to find that the polycrystalline modules often perform better than their monocrystalline counterparts. Here’s a link to California’s PTC ratings for solar panels to help you make informed decisions on your purchases:
There are a few more factors that should weigh in on your decision. It’s important to research to watts generated per square foot, or “WPSF.” Additionally, the power tolerance is something you want to think about before you make a purchase. Solar modules, even when labeled a specific wattage, have some variance. It is common for a model to be within a range of +/- 3%, or +/-5%. If a module has a power tolerance of +/-5%, it may only be able to yield 95% of its nameplate rating.
Whether you’re thinking about installing a solar system with monocrystalline or polycrystalline modules, one of the most important things to consider is the manufacturer of the panels. When it comes to solar, not all brands are created equal. Just to name a few, we recommend Sharp, Canadian, and Yingli. Also, be sure to carefully consider what kind of inverter(s) you will using in your system, since this can greatly impact the system overall. Enphase microinverters are usually a great choice.
Whenever you’re shopping for a solar module, you should take all this information into consideration. If you have any questions, you’re welcome to give us a call at (866) 798-4435.