Types of solar panels: The efficient, the cheap and the flexible

There are 3 main types of solar panels: monocrystalline, polycrystalline and thin-film solar panels, plus there are some special cases that are not so widely spread. These types vary in cost, performance, aesthetics and durability that determine their lifespan. Let's look at each one in more detail.

Monocrystalline panels stand out in line because of their amazing performance. Their efficiency often exceeds 20%. Making monocrystalline panels is a slow and expensive process: a single crystal of silicon is sliced into wafers that are used to make solar cells. A completed panel has a black color and contains 60, 72 or 96 cells. Edges of these cells are rounded. Black panels look stylish and sometimes their design is what makes customers choose them.

The biggest drawback of monocrystalline panels is their cost. Although their efficiency is higher, it doesn't always make the payback time shorter. Generally, they sell for 5 cents higher per watt than polycrystalline ones. Their lifespan is the highest, and the warranty for them can be issued for up to 25 years.

Monocrystalline panels are the best choice when space on the roof is limited or when a roof can't withstand high weights. Due to the same reasons they are oftentimes used on ships. Their construction allows them to perform well even in low-light situations — like bad weather or during months of fall.

Polycrystalline panels have one big difference production-wise when compared to monocrystalline ones. Instead of a single crystal, a block of silicon is being used. They also contain 60, 72 or 96 cells. Cells have a square shape and are blue in color. Frames are often silver or white. This design doesn't always appeal to customers in contrast to much more stylish black monocrystalline panels. So the appearance might be called a drawback for polycrystalline panels.

Because of the use of multiple crystals, the performance of polycrystalline panels drops a little. Usually their efficiency ranges from 15% to 20%. However, the production process is much cheaper, which is reflected in the cost — they are 20-25% cheaper than monocrystalline panels. Their durability is on par with monocrystalline panels and they can easily last for 25 years or longer. They are a great choice for those who aren't ready to invest a lot into solar energy, and they often give the fastest payback time.

Thin-film solar panels are much more different than monocrystalline or polycrystalline ones. In the process of making them photovoltaic material is being applied onto glass or metal substrate. This modern technology allows thin-film panels to be the cheapest of all types, plus they are the easiest to install.

In theory these panels are very thin, however it depends on substrate and varies from model to model. They also can be quite flexible, unlike other types of solar panels, and very light-weight. Thin-film solar panels can vary in appearance and can be black or blue, depending on a particular model. Unlike other examples, they aren't produced with a fixed number of cells, which depends on their size.

Being the cheapest comes with the cost: thin-film solar panels have the lowest efficiency of all types. It usually varies around 10%-13%. What is more, their lifespan is considerably shorter — they usually don't last longer than 20 years, which means that an owner might have to replace them more often. In most cases they are not suitable for residential use — there is not enough space to justify using them. However, they are a great choice for mobile installations mobile installations.

Now that we have looked closely at each type of most widespread solar panels, we can use a chart to make this information look more structured.

While these 3 types of solar panels are the most prominent, there are other options that can be good in certain situations. For example, there are integrated solar cells. These are used in times when the appearance of a building shouldn't be affected by solar panels at all so they are built into walls or a roof. These building-integrated photovoltaics (BIPVs) are expensive and considerably less efficient than other counterparts but let you keep the original design of a house or a building. This might be a good option for those who are considering building a new home from scratch.

Bifacial solar panels can be counted as a subcategory of monocrystalline or polycrystalline panels. Their distinctive feature is the ability to capture the sunlight with its back side as well the front. It makes them on average 11% more efficient than comparable polycrystalline/monocrystalline modules.

Bifacial panels often have a transparent black sheet, so that sunlight can go through the panel and reflect from the ground back onto the panels. They are rarely useful for homeowners who consider a rooftop installation, but can be effective as ground-mounted systems. They are best suited for commercial or utility-scale use.

There are new types of solar panels that are currently being developed and in the future they might replace those that are more common now. Right now they are either not ready or too expensive for residential use to even take them into consideration.

For example, there is Biohydrate Solar Cell technology, which emulates the process of natural photosynthesis (right now in development). Cadmium Telluride Solar Cells (CdTe) allow the production of solar panels to become much cheaper but have a significant drawback — they are toxic. Concentrated PV cells take advantage of mirrors, lenses, cooling systems and solar trackers, which allow them to reach the efficiency of 41%.

Every model of solar panel undergoes testing before going on market. Apart from tests on efficiency, engineers check on how panels are made to endure extreme conditions. For example, panels should remain undamaged under hail at a speed from 20 to 30 m/s.

Also manufacturers look at how panels perform at high temperatures. In Standard Test Conditions performance of solar panels is measured at 77 degrees Fahrenheit (this is the temperature of a cell). When it gets hotter, panels start to gradually lose their efficiency. Their ability to retain it can be measured through their temperature coefficient. For monocrystalline and polycrystalline panels it ranges from -0.3 % to -0.5% per degree after 77. For example, if the temperature of your modules rose to 87 degrees, they lose from 3 to 5% of their efficiency. Thin-film panels are more resistant: their temperature coefficient is closer to -0.2%. Keep in mind that the temperature of panels installed on the roof is much higher than ambient temperature.

Now that you know more about the properties of different types of solar panels, it's easier to answer the question "Which one should I choose?" For residential use the best option is usually monocrystalline panels. However if you're tight on funds, polycrystalline panels are a fine choice. Don't forget that it is possible to save 30% of the installation cost with Federal Solar Tax Credit (read about it in our article).