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Monocrystalline or Polycrystalline?

Most solar modules used today are either polycrystalline or monocrystalline, otherwise known as mono and poly.

So what is the difference between poly and mono?

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.

Though there are subtle differences between the two, neither technology is necessary better than the other.

Monocrystalline

Monocrystalline, which is also called mono or 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.

A monocrystalline solar cell is composed of a single crystal of silicon, a purity that can be identified by a dark, even coloring.

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.

Monocrystalline solar panel panels will typically have higher efficiency rates (15-20%), converting energy particularly well in low-light and lab conditions.

Because monocrystalline solar cells usually have higher efficiency, these solar panels will make good use of limited roof space.

Though monocrystalline cells function well in low-light conditions, elevated heat can cause the conversion rate to decrease more than polycrystalline panels.   Monocrystalline cells have a long life and are very durable.

Monocrystalline technology is typically more expensive than other solar technologies, including polycrystalline.

Pros:

• High efficiency

• Performs well in low-light conditions

Cons:

• Usually more expensive

• Sensitive to soiling and shade

• More silicon is wasted in the manufacturing process

Polycrystalline

Polycrystalline, which is also called poly or multicrystalline, has been used since 1981. Polycrystalline solar panels are easily identified by their solar cells that have a textured look resembling a granite countertop or shattered glass.

Polycrystalline cells are composed of multiple silicon crystals, which 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.  Just remember that “poly” means “many,” so it has many crystals.

Canadian Solar CS6P-240P, 240 Watt Polycrystalline Solar Panel

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.

Pros:

• Cost-effective

• Manufacturing produces less waste

Cons:

• Doesn’t perform as well in low-light conditions

• Aesthetics? You can be the judge of this.

• Lower efficiency

So… Mono or Poly?

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.

The short answer is that it’s difficult to say one way or the other because there are a number factors to consider, including the solar panel’s PTC rating, warranty, your geographical location and solar insolation.   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:

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’s common for a solar panel to be within a range of +/- 3%, or +/-5% of its rated output.  If a module has a power tolerance of +/-5%, it may only be able to yield 95% of its nameplate rating.

In the past, monocrystalline panels were considered better because, in addition to the purity of their silicon, they’ve also had traditionally higher peak efficiency. Polycrystalline technology has improved to the point that monocrystalline cells do not necessarily mean a better solar panel.

Whether you’re thinking about installing a solar system with monocrystalline or polycrystalline modules, you ought to consider quality of the manufacturer and the warranty behind the product. 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 the brandname and warranty behind the inverter(s) you choose.   SMA SB 3000US Sunny Boy Grid Tie Inverter or Enphase microinverters, for example, have warranties that are backed by trusted companies.

When you’re shopping for a solar system, there can information into account.

Talk with a qualified solar installer about the best choice for your specific application.

If you have any questions, you’re welcome to give us a call at (866) 798-4435.

Author: Tom Jackson

I believe in a future that’s powered by clean energy. "Idealist" should not be a dirty word.

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