Monocrystalline vs polycrystalline solar panels: The difference explained

The key part of any solar panels are solar cells. They are made of photovoltaic material, which allows them to produce current under the sun. Almost all solar cells are made of silicon, a component of beach sand. First, silica sand is exposed to high temperatures in the furnace. Once you have a pot of melted silicone, the process starts to differ for monocrystalline and polycrystalline panels.

To make polycrystalline solar cells, hot silicon is poured into a square mould. As it cools down, it forms many rocks or so called crystals. Then this silicone ingot gets sliced into thin wafers. They are of a perfect square shape: when they are laid up into a panel, there is no wasted space.

The process of making monocrystalline solar cells is more complicated. First, manufacturers grow a single large crystal from melted silicone. This process is called Czochralski and reminds of making cotton candy. In the end, they get a big silicon cylinder. If it were sliced as it is, wafers would be round discs, which couldn't be efficiently packed into a solar panel. There would be gaps between the cells, leaving parts of the solar panel surface inactive. So the cylinder is first cut along its length on four sides to get wafers of a square shape with rounded corners (pseudo-square). The remnants of the manufacturing process are later used for making polycrystalline cells.

The wafers, both poly- and monocrystalline, are usually polished to remove saw marks. However, it increases their reflectivity up to around 40%, which means a lot of sunlight is wasted. Anti-reflective coating used for polycrystalline panels lowers it down to 6% and gives solar modules their distinctive blue hue. A special modern technology is used to make "black silicone", the standard for monocrystalline panels. Their reflectivity goes even further down to 1.5%.

Solar cells are the most important, but aren't the only component of PV modules. If you want to know more about the manufacturing process of solar panels and how they work, check out our article.

Now let's look at each type of solar panels closer to figure out which situations they suit the best.

Monocrystalline panels are easy to recognise by their looks: the cells have rounded corners and black color, which people usually find more stylish.

The main selling point of monocrystalline modules is their high efficiency, going over 18%. It is achieved due to their cell structure, allowing electrons to move more freely than they do in polycrystalline panels. High efficiency means that you are going to get more electricity from a square foot and use the space of your roof or yard in the most effective way. Therefore, monocrystalline panels are an obvious choice when space is limited, like boats, RVs or even small vehicles.

Monocrystalline solar panels also perform better than other types of panels in low-light conditions: on cloudy days and in the winter. High temperatures also affect them less than polycrystalline panels.

However, since the manufacturing process is rather complicated and wasteful, it reflects on their cost. Monocrystalline modules tend to be 20-25% more expensive than polycrystalline panels of the same wattage.

Polycrystalline panels are made of multiple silicon crystals, which give them the look of a shattered glass or marble. The cells are often blue with square corners.

Manufacturing process of polycrystalline cells is easier and cheaper, but melting together many silicon crystals obstructs the flow of electrons in a panel and lowers its efficiency. It ranges from 15% to 20% maximum. Since polycrystalline panels are less efficient than monocrystalline ones, they are going to occupy more space while costing less. If you don't want to invest too much in a solar panel system, have enough free room on the roof or in the yard and don't really care about getting as much energy as possible, polycrystalline panels are your go-to choice.

There is, however, some data on higher tolerance to shading. Some companies claim that polycrystalline panels still work fine under layers of snow or dust, whereas monocrystalline panels are more likely to malfunction.

One drawback of polycrystalline panels is their vulnerability to heat. Not only hot weather decreases their performance, it can potentially shorten their lifespan. If you live in a particularly hot area, like Texas or Arizona, trying to save money by purchasing polycrystalline solar panels may turn out to be a mistake in the long run.

Efficiency and cost are the main points where polycrystalline and monocrystalline solar panels differ from each other. Their lifetime on paper exceeds 25 years, and warranties for them are issued accordingly. Keep in mind that manufacturers often guarantee that solar panels performance isn't going to fall below a certain point – usually, no less than 90% in the first 10 years and no less than 80% in the decade after that.

Now that we've studied the main properties of both types, let's summarize:

Currently, monocrystalline panels are a more popular choice for residential solar systems. While polycrystalline panels do cost less, this difference in price is not convincing enough. It's possible that their vulnerability to heat also repels potential customers from choosing polycrystalline panels as solar panels are more popular in sunny, hot cities, like Los Angeles. Finally, aesthetics play their part: black color of monocrystalline panels just looks better on the roof.

As a result, more and more manufacturers move away from polycrystalline panels in favor of other types of photovoltaics. However, some brands keep experimenting with poly-modules and use the latest innovations with them. For example, in 2014 REC introduced Twinpeak, a polycrystalline panel with half-cut cell design, which allowed the module to compete with mono-panels in terms of production and efficiency. Canadian Solar offers bifacial panels BiHiKu which can be either poly or mono.

Although monocrystalline and polycrystalline panels are widespread, it doesn't mean they are the only ones in the market. Check out our article to learn about other types of solar panels.