Solar panel efficiency: most efficient solar panels in 2021

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most efficient solar panels in 2021
The SunPower A-Series high efficiency solar panel. Image source: SunPower

One important thing to consider when shopping for solar panels is the solar panel efficiency rating. The efficiency of a solar panel gives you an idea of how much energy your solar panel system will be able to produce. 

But what exactly is solar panel efficiency and what factors impact it? What high efficiency panels are currently on the market? We explore that - and more - with our breakdown of solar panel efficiency. 

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    What is solar panel efficiency?

    Solar panel efficiency is a measure of how much sunlight that hits the surface area of a solar panel that is converted into usable electricity. 

    The higher the efficiency rating, the more sunlight your solar system can turn into electricity to power your home. So, if a solar panel has an efficiency rating of 15%, that means 15% of the sunlight that hits the solar panel will be converted into electricity. 

    Want more information? Check out this video of SolarReviews founder Andy Sendy providing an in-depth review of what solar panel efficiency means:

    How efficient are solar panels?

    According to the National Renewable Energy Laboratory (NREL), most solar panels sold in 2021 are between 15% and 20% efficient. Some solar panels on the market even have efficiencies of over 20% - these are known as high efficiency or premium efficiency solar panels.

    Premium efficiency solar panels come at a higher price than standard efficiency panels. However, as solar technology has improved over the years, average solar cell efficiency ratings have increased. At the same time, the cost of solar has continued to decrease. 

    That means you now get solar that is cheaper and more efficient than ever!

    Find out how much you can save annually by installing solar panels

    How do you calculate solar panel efficiency?

    When you’re shopping for solar panels, the efficiency rating will be listed on the panel’s datasheet. But how exactly is that efficiency rating calculated?

    All solar panels are tested at an operating temperature of 25*C with solar irradiance (or the amount of sunlight hitting the panel) of 1,000 watts per square meter. These are called Standard Test Conditions or STC for short. 

    So, to find the efficiency of a panel under STC, divide the power rating by the area of the panel times the irradiance, times 100. 

    solar panel efficiency at standard test conditions

    But the solar panels on your roof won’t be operating under STC. In the real world, the irradiance level and temperature will vary and change your panel’s efficiency. However, those aren’t the only factors that will affect solar panel efficiency. 

    What are the most efficient solar panels in 2021?

    Right now, SunPower manufactures the most efficient residential panel on the market, the Series A, which boasts a whopping 22.5% efficiency rating. 

    There are a few other solar panel manufacturers that produce premium efficiency panels, which all clock in at efficiencies above 20%. 

    The following table lists some of the highest-efficiency solar panels available in the U.S.:

    Manufacturer Wattage Efficiency
    SunPower A-Series 420 W 22.5%
    LG NeON R 375 W 21.7%
    REC Alpha Series 380 W 21.7%
    Panasonic EverVolt 370 W 21.2%
    Jinko Solar Eagle 78 TR G4 475 W 21.16%

    These solar panels have higher-than-average efficiencies and also come with a higher price tag. With that said, keep in mind that your solar panel installation could end up costing you more money if you plan to use these high efficiency panels

    What affects solar panel efficiency?

    Solar panel efficiency is impacted by many things, but it’s mostly impacted by environmental conditions and how the panels are manufactured. 

    Type of solar cell 

    The solar cell technology used in the panel plays a large part in how efficient the panel will be. 

    As a general rule, monocrystalline panels will have a higher efficiency than polycrystalline solar panels. Most premium-efficiency solar panels are made with monocrystalline silicon solar cells. 

    Learn more: Monocrystalline vs. polycrystalline solar panels

    Monocrystalline solar cells are made of one singular crystal of silicon, which allows for electrons to easily travel through the cell and increase the panel’s efficiency. Polycrystalline cells are made of multiple crystals, so it’s not as easy for electrons to pass, making them slightly less efficient. 

    There are also thin-film solar panels, which are sometimes referred to as ‘amorphous silicon panels’. Thin-film solar cells are flexible and lightweight, but extremely inefficient. They are rarely used in the residential solar industry. 

    Temperature 

    Ironically, despite the fact that they make energy from the sun, solar panels actually operate better at colder temperatures. 

    As solar panels get hotter, the current increases while the voltage decreases, causing the overall output of the panels to drop. This means your solar panels will operate the most efficiently in the winter, even though they’re getting less sunshine. 

    When we say ‘temperature’, we don’t mean the temperature on your weather app. We’re talking about the surface temperature of the solar module itself. The surface temperature does have to do with the weather, as your panels will get much hotter under the summer sun than they will on a winter afternoon. 

    Backing color 

    The color of the back of your solar panel may also impact the efficiency of your panels. 

    Black backing causes the panels to stay hotter, as black absorbs more light. This will make the efficiency of your panels lower. 

    White backing, on the other hand, might not look as nice as a black back sheet, but will keep your solar panels cooler and their efficiency higher. 

    Wiring and busbars 

    When you look at the surface of a solar panel, you’ll see a series of wires and busbars, which are what wire solar cells together. These are what actually transfers the electricity through your panel. 

    The more busbars there are, the more electrons can pass through, which can increase the overall efficiency of the panel. 

    However, having too many busbars can actually decrease the efficiency, because more of the solar cells will be covered. That’s why companies like Solaria have created a ‘no busbar’ product that increases how much of the panel is actually covered by solar cells. 

    Dust, dirt, snow, and other debris 

    Solar panels are exposed to the elements, which means they’ll get dirty. If there is dust or dirt on your panels, less sunlight will be reaching the solar cells. 

    Cleaning solar panels regularly is a great way to ensure they are operating as efficiently as possible. 

    Advantages of high efficiency solar panels

    Despite the good reviews and popularity of standard efficiency panels, there are some clear-cut advantages of high efficiency solar panels - one of which being that they will produce more electricity over the lifetime of the solar system. 

    As solar panels get older, their ability to convert sunlight into solar power drops. Since premium efficiency panels already start with a high efficiency rating, as they degrade, they will still be relatively efficient. This means they can have higher energy production over the lifespan of the system as compared to standard efficiency panels

    Besides producing more energy over time, high efficiency solar panels have the ability to produce more energy per square foot of roof space. This is because they turn more of the sunlight that hits the roof into solar energy. 

    If you have a limited amount of space on your rooftop where solar can be installed, premium efficiency panels may be the best solar panels for your home.  

    See how many solar panels can fit on your roof using our drawing tool

    Is it always better to get high efficiency solar panels?

    In most cases, you can get high-quality, standard-efficiency solar panels and cover all of your electricity needs. Then, you don’t have to worry about paying a premium for the extra efficiency. 

    You’ll only really need to invest the extra money in high efficiency panels if you have limited roof space for a solar energy system. Plus, standard solar panel efficiency is much higher than it used to be, so your standard panels will still convert a lot of sunlight into solar power for you to use. 

    Here are some popular, highly-reviewed standard efficiency solar panels:

    What to look for when shopping for solar panels

    Solar panel efficiency is just one thing to consider when shopping for solar panels. Some other things to consider are:

    • Power output rating
    • Warranty
    • Brand

    It’s important to remember that just because a solar panel is the most efficient, doesn’t mean that it’s the best for your home. Your solar installer will be able to help you find the right solar panels to meet your energy needs.

    That’s why it’s important to get quotes from multiple solar installers to make sure you get the best quality solar installation at the best price. You can also use our solar panel calculator to get a personalized estimate for how much a solar installation would cost for your specific home.

    See which solar panels work best for your specific home

    Key takeaways

    • Solar panel efficiency measures how much of the sunlight that hits a s solar panel turns into usable electricity.
    • Most solar panels used today have efficiencies between 15% and 20%. SunPower’s Series X is the most efficient solar panel with an efficiency rating of 22.8%.
    • The biggest influences on solar panel efficiency are the type of wiring, the color of the backing, and the type of solar cells used.
    • Premium efficiency solar panels are really only necessary if you have limited roof space, as they can produce more electricity in a smaller area.
    • In most cases, you can install high-quality standard efficiency solar panels while meeting all your electricity needs at a lower cost.
     - Author of Solar Reviews

    Catherine Lane

    SolarReviews Blog Author

    Catherine is a researcher and content specialist at SolarReviews. She has strong interests in issues related to climate and sustainability which led her to pursue a degree in environmental science at Ramapo College of New Jersey.

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