Which Solar Panel Type is Best? Mono- vs. Polycrystalline

You are thinking about buying solar panels, but got confused about which type to go for? You’re at the right place. There’s a myriad of variables that you should take into account when you are buying a solar photovoltaic (PV) system – our job here at Energy Informative is to help you sort through them!

In this article, you will learn everything you need to know about the different types of solar panels for home use (mono-, polycrystalline.

Let’s start with the different types of solar panels currently on the market, list their benefits and downsides, and then look at a few typical scenarios where certain types would be the better than others (hopefully one of them resonates with you).
 

Contents

• Crystalline Silicon
• Monocrystalline
• Polycrystalline
• Best Solar Panel Type for Home Use

Crystalline Silicon (c-Si)

Almost 90% of the World’s photovoltaics today are based on some variation of silicon.^[1] In 2011, about 95% of all shipments by U.S. manufacturers to the residential sector were crystalline silicon solar panels.

The silicon used in PV takes many forms. The main difference is the purity of the silicon. 

But what does silicon purity really mean? The more perfectly aligned the silicon molecules are, the better the solar cell will be at converting solar energy (sunlight) into electricity (the photoelectric effect).

The efficiency of solar panels goes hand in hand with purity, but the processes used to enhance the purity of silicon are expensive. Efficiency should not be your primary concern. As you will later discover, cost-and space-efficiency are the determining factors for most people.

 

Monocrystalline Silicon Solar Cells

Solar cells made of monocrystalline silicon (mono-Si), also called single-crystalline silicon (single-crystal-Si), are quite easily recognizable by an external even coloring and uniform look, indicating high-purity silicon, as you can see on the picture below:

Monocrystalline solar cells are made out of silicon ingots, which are cylindrical in shape. To optimize performance and lower costs of a single monocrystalline solar cell, four sides are cut out of the cylindrical ingots to make silicon wafers, which is what gives monocrystalline solar panels their characteristic look.

A good way to separate mono- and polycrystalline solar panels is that polycrystalline solar cells look perfectly rectangular with no rounded edges.

Advantages

• Monocrystalline solar panels have the highest efficiency rates since they are made out of the highest-grade silicon. The efficiency rates of monocrystalline solar panels are typically 15-20%. SunPower produces the highest efficiency solar panels on the U.S. market today. Their E20 series provide panel conversion efficiencies of up to 20.1%.  SunPower has now released the X-series at a record-breaking efficiency of 21.5%.
• Monocrystalline silicon solar panels are space-efficient. Since these solar panels yield the highest power outputs, they also require the least amount of space compared to any other types. Monocrystalline solar panels produce up to four times the amount of electricity as thin-film solar panels.
• Monocrystalline solar panels live the longest. Most solar panel manufacturers put a 25-year warranty on their monocrystalline solar panels.
• Tend to perform better than similarly rated polycrystalline solar panels at low-light conditions.

Disadvantages

• Monocrystalline solar panels are the most expensive. From a financial standpoint, a solar panel that is made of polycrystalline silicon (and in some cases thin-film) can be a better choice for some homeowners.
• If the solar panel is partially covered with shade, dirt or snow, the entire circuit can break down. Consider getting micro-inverters instead of central string inverters if you think coverage will be a problem. Micro-inverters will make sure that not the entire solar array is affected by shading issues with only one of the solar panels.
• The Czochralski process is used to produce monocrystalline silicon. It results in large cylindrical ingots. Four sides are cut out of the ingots to make silicon wafers. A significant amount of the original silicon ends up as waste.
• Monocrystalline solar panels tend to be more efficient in warm weather. Performance suffers as temperature goes up, but less so than polycrystalline solar panels. For most homeowners temperature is not a concern.

Polycrystalline Silicon Solar Cells

The first solar panels based on polycrystalline silicon, which also is known as polysilicon (p-Si) and multi-crystalline silicon (mc-Si), were introduced to the market in 1981. Unlike monocrystalline-based solar panels, polycrystalline solar panels do not require the Czochralski process. Raw silicon is melted and poured into a square mold, which is cooled and cut into perfectly square wafers.

Advantages

• The process used to make polycrystalline silicon is simpler and cost less. The amount of waste silicon is less compared to monocrystalline.
• Polycrystalline solar panels tend to have slightly lower heat tolerance than monocrystalline solar panels. This technically means that they perform slightly worse than monocrystalline solar panels in high temperatures. Heat can affect the performance of solar panels and shorten their lifespans. However, this effect is minor, and most homeowners do not need to take it into account.

Disadvantages

• The efficiency of polycrystalline-based solar panels is typically 13-16%. Because of lower silicon purity, polycrystalline solar panels are not quite as efficient as monocrystalline solar panels.
• Lower space-efficiency. You generally need to cover a larger surface to output the same electrical power as you would with a solar panel made of monocrystalline silicon. However, this does not mean every monocrystalline solar panel perform better than those based on polycrystalline silicon.
• Monocrystalline and thin-film solar panels tend to be more aesthetically pleasing since they have a more uniform look compared to the speckled blue color of polycrystalline silicon.

Best Solar Panel Type for Home Use

Having your particular situation evaluated by an expert would be the best way to find out what solar panel type would be best for your household. Here are some of the typical scenarios we see:

Limited Space

For those who don’t have enough space for thin-film solar panels (the majority of us), or if you want to limit the amount of space their PV-system takes up, crystalline-based solar panels are your best choice (and they would likely be the your best choice even if you had the extra space). There are not a whole lot of solar installers and providers that offer thin-film solar panels for homeowners at this point.

You will have a choice of different solar panel sizes. The 180, 200 and 220-watt rated solar panels are usually physically the same size. They are manufactured exactly the same way, but under- or overperform when tested, hence ending up in different categories for power output. If size is important, you should go for the highest rated power output for a particular physical size.

Both mono- and polycrystalline solar panels are good choices and offer similar advantages. Even though polycrystalline solar panels tend to be less space-efficient and monocrystalline solar panels tend to produce more electrical power, this is not always the case. It would be nearly impossible to recommend one or the other by not examining the solar panels and your situation closer.

Monocrystalline solar panels are slightly more expensive, but also slightly more space-efficient. If you had one polycrystalline and one monocrystalline solar panel, both rated 220-watt, they would generate the same amount of electricity, but the one made of monocrystalline silicon would take up less space.