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. Generally speaking, mono solar panels are more efficient but poly solar panels are a better use of your money.
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. 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. Mono panels will generally have higher nameplate ratings than poly. Because monocrystalline solar cells usually have higher efficiency, these solar panels will make good use of limited roof space.
The biggest draw-back is cost. Mono solar panels come at a premium so unless you’re particularly limited on roof space, they’re not the best use of your money.
• High efficiency
• Good for limited space
• Performs well in low-light conditions
• High Cost
• Sensitive to soiling and shade
• More silicon is wasted in the manufacturing process
Polycrystalline, which is also called poly or multicrystalline, has been used since 1981. Until recently, polycrystalline solar panels were easily identified by their solar cells that have a textured look resembling a granite countertop or shattered glass. Most poly solar panels just have a dark blue color now.
Polycrystalline cells are composed of multiple silicon crystals, which is a cheaper way to manufacture solar modules. Polycrystalline cells are commonly made with a cast of molten silicon. When these cells are being created, they cool faster, creating smaller crystals. Just remember that poly means many because it has many crystals. Because poly solar panels are easier to produce, they’re less expensive – making them the ideal choice for most people.
Though monocrystalline is still more efficient at energy conversion in lab settings, polycrystalline has been quickly catching up.
• Cost-effective in terms of $/Watt
• Manufacturing produces less waste
• Doesn’t perform as well in low-light conditions
• Not ideal for very limited square footage
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 high efficiency solar panels do not mean they’re the most efficient use of your money. Generally speaking, poly solar panels are offered at a lower dollar per Watt, meaning a faster return on your investment. Just as solar panels cost more per Watt when you opt for higher output panels, there is a premium paid for mono solar panels. If you’re trying to maximize the output of your system from limited roof-space, monocrystalline might be the right choice for you. Most customers, however, are truly looking to get the most kWh from their money. In this case, poly solar panels are a better value because the $ per Watt is lower.
There are a number other factors to consider when choosing a panel, including the solar panel’s PTC rating, warranty and the support from the company offering the product.
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 actually 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. More importantly, high efficiency solar panels do not mean they’re the most efficient use of your money.
Whether you’re thinking about installing a solar system with monocrystalline or polycrystalline modules, also consider quality of the manufacturer and the warranty behind the product. Just about all solar panels will have a 25-year power output warranty but some companies have been around longer than others. SMA SB 3000US Sunny Boy Grid Tie Inverter or APSystems or Enphase microinverters, for example, have warranties that are backed by trusted companies. Also note that with string inverters, you’re usually not going to get a warranty that will last the life of the system.
When you’re shopping for a solar system, there can information into account. Let us help you today. Gather your kWh usage from the last 12 months, the size of your Main Service Panel (MSP), and call (866) 798-4435 to talk with one of our solar consultants.