Whether you’re embarking on a small-scale DIY solar project or planning to cover an entire roof with panels, one of the first decisions you’re likely to make is deciding between monocrystalline or polycrystalline solar panels.
This article will lay out the major differences between the two, and the pros and cons of each type, to help you decide which is best for your needs.
Monocrystalline and polycrystalline solar panels are two of the main types of solar panels on the market today. They are the most popular options for residential and commercial installations, as well as DIY solar projects.
They are both made from silicon solar cells. The cells are coated with other elements, such as boron and phosphorus, so that they have positively and negatively charged sides. And both have silver wires printed onto the wafers to allow for electricity to flow once sunlight knocks loose electrons from the silicon atoms.
They are manufactured differently, however, which leads to slight differences in factors such as their cost and efficiency.
Monocrystalline solar panels have solar cells that are made of a thin wafer of a single crystal of nearly pure silicon. It’s expensive to manufacture pure crystals for monocrystalline panels, which is why they cost more than polycrystalline panels.
But the purity of monocrystalline panels makes them more efficient. The most efficient on the market are currently around 22-24% efficient, meaning they can convert 22-24% of the light shining on them into usable solar energy.
A close-up of a monocrystalline solar panelMonocrystalline crystals are arranged in a uniform alignment that absorbs more sunlight and refracts less. As a result, monocrystalline panels appear black. (However, some mono panels can sometimes appear dark blue.)
By contrast, polycrystalline solar panels have cells that are made from silicon crystal fragments. The fragments are melded together in an oven and formed into cubes, which are then cut into wafers. The manufacturing process is less error-prone than slicing wafers off of a single crystal, so it costs less and wastes fewer raw materials. As a result, polycrystalline solar panels are cheaper.
However, they’re also less efficient. The best polycrystalline solar panels are currently around 17-20% efficient. Their being less efficient doesn’t mean they output less power than monocrystalline solar panels. It just means that a poly panel must be bigger — that is, it must have more surface area — to be able the output the same amount of power as a comparable mono panel.
A close-up of a polycrystalline solar panel. Note the slightly fractured appearance due to silicon fragments being melted together.Being manufactured from multiple crystals, impurities in the polycrystalline cells scatter more light than monocrystalline panels do. That’s the main reason they look blue, just as our atmosphere scatters light to make the sky look blue.
Note: Monocrystalline and polycrystalline solar panels are usually rigid. However, you can also buy flexible solar panels, which are most often monocrystalline solar panels. The wafers in flexible panels are even thinner than those in rigid panels, which is what allows them to be flexible.
The pros and cons of monocrystalline and polycrystalline cells come down to their basic physical difference. The major differences between the two are price and efficiency.
Monocrystalline panels cost $1.00 to $1.50 per watt, on average, while polycrystalline panels on average cost $0.90 to $1.00 per watt. It costs more to shave a thin wafer off a single silicon crystal than it does to fuse together silicon fragments.
Both types of solar panels require framing, wiring, and — for residential solar panels — inverters, for which the cost is the same. Both are also likely to qualify for federal and state tax credits or rebates, where available.
For example, a 100 watt solar panel — a common size for DIY solar projects — will run you about $80-100 for a polycrystalline panel and $90-120 for a monocrystalline panel.
Monocrystalline panels more efficiently convert sunlight into electricity than polycrystalline panels do – from 20% to 24% efficient for monocrystalline panels compared to 13% to 20% for the polycrystalline.
The simpler flower of electrons in monocrystalline panels also allows them to perform better in higher temperatures than polycrystalline panels do. Heat tolerance is measured in a temperature coefficient, which is the rate at which the power output of photovoltaic cells drops for every degree they are above 25°C (77°F). The greater the temperature coefficient, the less power the panel will output as it heats up.
Tip: There are other types of solar panels to choose from, but monocrystalline and polycrystalline are the two most common. Emerging technologies like perovskites, organic cells, and quantum dots are reaching levels of efficiency in research labs that may some day allow them to replace silicon solar panels altogether. But don’t put off your DIY project or residential install because you’re worried the tech you’re using will soon be outdated. Solar energy is so much cheaper than non-renewable alternatives that starting a project today means avoiding costs that you would otherwise incur. I know first-hand: I bought my solar panels in 2017, when the price for solar was higher than it is today. But energy prices today are a lot higher than they were in 2017, and the higher energy prices go, the more I’m glad I didn’t wait.
As with many purchases, quality costs more. But just as you don’t need to buy an expensive gaming computer with the latest Nvidia chip when all you do is check your email and look at cat videos, there’s no need to buy more quality than you need.
In general, monocrystalline panels cost more, but they are also more efficient, so they provide more electricity per square meter. Often, the extra price of monocrystalline panels is about the same as their extra efficiency, so you do get your money’s worth if you spend more. But monocrystalline panels are also a bit more durable, so they can give you more power over a longer lifetime.
The main factors to consider when deciding between monocrystalline and polycrystalline panels are price, space, climate, durability, and color.
If you’re only considering price in your decision, do a simple calculation to determine the cost per year of each type of solar panel over their lifespan. Figure out how many panels of each type you would need, and total up their costs. Also note their performance warranty as a proxy for their expected lifespan.
For example, let’s say you want to solar power your RV. You determine that you need 400 watts to meet your energy needs. That works out to four 100 watt mono panels or four 100 watt poly panels. The total cost of the mono panels is $480 and they have a 25-year, 80% output performance warranty. The cost of the poly panels is $400 and they have a 20-year, 80% output performance warranty.
Here’s the per-year cost of the monocrystalline panels:
$480 ÷ 25 years = $19.20 per year
And here’s the per-year cost of the polycrystalline panels:
$400 ÷ 20 years = $20 per year
In this example, the polycrystalline panels are actually more expensive on a per-year basis, despite having a lower upfront cost. And that’s not even considering the slightly more power the monocrystalline panels will likely output due to their better heat tolerance.
If you have limited mounting space, monocrystalline panels are a better option due to their higher efficiency and better power-per-square-foot ratio. But if you have ample space to install solar panels — such as when ground-mounting or installing them on a large roof — you can buy cheaper poly panels.
On average, a monocrystalline panel will be more efficient in high temperatures than a polycrystalline panel will be. The higher your year-round temperatures, the more that buying monocrystalline panels is a smart decision, since temperature coefficient differences begin to add up.
For instance, a polycrystalline panel with a temperature coefficient of -0.5% means its power output will drop by half a percent for every degree above 25°C (77°F). A monocrystalline panel with a -0.25% temperature coefficient loses only a quarter of a percent of its power output for every degree above 25°C.
If it’s 100°F (38°C) out, a 200-watt monocrystalline panel will be 3.25% less efficient, while a 200-watt polycrystalline panel will be 6.5% less efficient. To match the power output of a monocrystalline panel in high temperatures, you’ll need to purchase a bigger polycrystalline panel, raising your costs.
Because of their simpler structure, monocrystalline panels are more durable, less susceptible to degradation from heat and exposure to UV light. The average warranty on monocrystalline panels is up to 30 years, while polycrystalline panels are more likely to be warrantied for 25 years.
Monocrystalline panels appear black, polycrystalline panels appear blue. Some people prefer mono panels because they think black panels look better on their roof.
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