Solar panel efficiency: The gap between the most efficient solar panels narrows in 2021

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5 most efficient solar panels lined up vertically left to right
The 5 most efficient solar panels. SunPower has the most efficient solar panel on the market. Images from: SunPower (#1), LG (#2), REC Group (#3), Upsolar (#4) and LONGi (#5)

SunPower has long held the title of the most efficient solar panels on the market. They are undoubtedly an excellent American solar company, and their 22.8% efficiency solar panels still remain at the top of the rankings in 2021.

But, it seems that SunPower is starting to lose its lead, as other leading manufacturers are starting to catch up. Now there are at least 10 other Tier 1 solar panel manufacturers with panel efficiency ratings above 21%.

Let’s take a look at the 2021 rankings for the most efficient solar panels from the market’s leading solar manufacturers, and see how they stack up.

Table 1. Most efficient solar panels in 2021
# Manufacturer Model Efficiency Power
Output
1 SunPower A-Series SPR-A425-G-AC 22.80% 425 W
2 LG Solar NeON R Ace LG405Q1C-A6 22.30% 405 W
3 REC Group Alpha Pure REC405AA 21.90% 405 W
4 Panasonic EverVolt EVPV380 21.70% 380 W
5 Upsolar Mono 182 UP-M560MH 21.60% 560 W
6 LONGi Hi-Mo 5m LR-72HPH 21.50% 550 W
7 Canadian Solar HiKu7 Mono Perc CS7N-665MS 21.40% 665 W
7 Silfab Solar Elite Sil-380 21.40% 380 W
9 JA Solar JAM72S30/MR 21.30% 550 W
9 Risen Energy Titan S RSM40-8-4-410M 21.30% 410 W
11 Seraphim SIV Series SRP-540-BMA-HV 21.13% 540 W
12 Jetion Jenius III JT545SGh 21.10% 545 W
13 Trina Solar TallMax TSM-DE15M(II) 20.90% 420 W
13 Suntech Ultra S STP455S-B72/Vnh 20.90% 455 W
13 S-Energy SN72 Half-Cell M6 Mono 20.90% 455 W
16 Yingli YLM 120 Cell YL380D 20.86% 380 W
17 Axitec Solar USA AXIpremium XL HC AC-450MH 20.70% 450 W
18 QCells Q.PEAK DUO BLK ML-G9+ 20.60% 385 W
19 Solaria PowerXT®-370R-PD 20.50% 370 W
20 Jinko Solar Eagle 66TR G4 20.43% 370 W
Note: This table excludes bifacial solar panels, which are unsuitable for home use.

Next, let’s go over some of the basics of solar panel conversion efficiency: what it means, how we measure it, and how much it actually impacts the amount of electricity your solar system generates.

We’ll also take a look at some real-world factors that can affect how efficient your solar panels actually are when they’re on your roof, rather than just the spec-sheet efficiency that is measured in a lab.

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    What is solar panel efficiency?

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

    (The conversion process is known as the photovoltaic effect, in which photons are separated from sunlight using semiconductors).

    The higher the efficiency rating, the more electricity the solar panel is able to produce from the amount of sunlight that shines on your roof. So, if a solar panel has a 15% efficiency rating , that means 15% of the solar energy within 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 is solar panel efficiency calculated?

    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.

    How solar cell technology determines the efficiency of solar panels

    Each solar panel is made of a number of individual silicon solar cells wired together. Different types of solar cells have different efficiencies, and companies continue to research and develop different methods so they can have the most efficient solar panels on the market. 

    SunPower, for example, has been able to lead the market in solar cell efficiency because of their Interdigitated Back Contact (IBC) solar cells they use in their modules. Not only are they highly efficient, the panels have a distinct look because you cannot see the connecting wires like you do with standard solar cells.

    While there are a number of different materials that solar cells can be made from, all of the most efficient panels on the market in 2021 use some type of monocrystalline silicon solar cell technology. (Polycrystalline solar cells, while cheaper, are less efficient).

    Most companies that have exceed 20% solar efficiency have done so using one or more of the following advancements in monocrystalline technology:

    PERC Solar Cells: Passivated Emitter and Rear Contact, more commonly referred to as PERC cells, were first developed in Australia back in 1983. Essentially, PERC cells are monocrystalline solar cells with a reflective back layer that reflects any light that may pass through back into the cell so it can extract more energy. PERC technology only provides about 1% of added efficiency, but it is a relatively cheap advancement, so companies can boost their efficiency without adding much to the manufacturing costs.

    HIT Solar Cells: Heterojunction with Intrinsic Thin Layer cells, or HIT cells, is a traditional monocrystalline solar cell that is sandwiched between layers of amorphous thin-film silicon. Amorphous silicon is able to utilize the light spectrum differently than the monocrystalline layer, so in total, slightly more solar power can be produced. 

    Originally developed by Sanyo, it was then sold to Panasonic and is the reason that Panasonic is constinstely near the top of the leaderboard in terms of efficiency. Recently, REC Group has also released a panel with an impressive 21.9% efficiency rating using this solar technology.

    Multi-busbar Technology: Some manufactures have found that using super thin wires to collect the electricity generated within the cells actually reduces shading on each cell, providing small efficiency gains.

    Split Cell Technology: Many manufactures split their solar cells in half in order to reduce heat and resistance within the cells which leads to small efficiency gains. Manufacturers like Canadian Solar and LONGi Solar have used split cell technology to achieve efficiencies around 21%

    How efficient are solar panels in 2021?

    According to the National Renewable Energy Laboratory (NREL), most solar panels on the market are between 15% and 20% efficient. But, what we’re seeing now in 2021 is that more solar manufacturers than ever have solar panels with quoted efficiencies over 20%.

    In fact, there are more than 20 solar manufacturers with efficiency ratings over 20%, and at least 10 manufacturers with efficiencies over 21%, narrowing the gap between SunPower’s market-leading 22.8% efficient panels and their competitors. 

    Tier 1 Chinese solar panels now offer high efficiency at a lower cost

    Premium efficiency solar panels like SunPower, LG, and Panasonic have always come at a higher price than standard efficiency panels. But, that’s all starting to change, as there are now several new Tier 1 Chinese solar companies that offer high-efficiency solar panels at a very low cost. 

    To give you an idea, at the wholesale level before installation, SunPower, LG, and Panasonic panels cost around $0.80 per watt. Some of their most efficient models are sold for as high as $1.00 per watt. Chinese solar manufacturing giants like Canadian Solar, Trina Solar, and LONGi, on the other hand, are now offering panels with efficiency ratings over 20% for about $0.40 per watt. 

    And these Chinese-owned companies are by no means back-alley manufacturers - they have some of the largest, most technologically advanced solar panel production facilities in the world. Canadian Solar, Trina Solar, and LONGi each manufacture more than 12 gigawatts (GW) of solar panels per year, while SunPower produces just 2.5 GW.

    This means that solar is not only cheaper than ever, it’s also more efficient than ever. The cheaper Chinese panels also begs the question: will the big three premium manufacturers be able to hold onto their price premium? This could particularly be an issue for SunPower, as their IBC cells are said to be more expensive to manufacture which could be a reason why SunPower chose to spin-off its manufacturing business, Maxeon Technologies, in 2020.

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

    How efficient are solar panels in real-world conditions?

    The efficiency quoted for each model of solar panel is calculated at Standard Test Conditions. However, in the real world solar panels seldomly operate in such conditions. In real-world conditions solar panel efficiency is impacted by things including:

    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 and making less overall power. 

    When we say ‘temperature’, we don’t mean the temperature on your weather app. We’re talking about the cell temperature within 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. 

    The amount by which the output of a panel reduces with heat above 25°C is referred to as the temperature coefficient. A smaller temperature coefficient means the output of a panel is less affected by extreme heat. SunPower and Panasonic have panels with the lowest-temperature coefficient on the market.

    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 and they will be less efficient. 

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

    Are the most efficient solar panels worth the higher price?

    If you have a limited amount of space on your rooftop, premium efficiency panels may be the best solar panels for your home. This is because they will allow you to install more solar generation capacity than you may otherwise be able to install on your roof.

    However, in terms of cost - there no longer seems to be a strong argument to pay a price premium for SunPower, LG or Panasonic solar panels given that the other Tier 1 solar panels are now almost as efficient and these manufacturers are also highly bankable companies.

    The wider availability of cheap high efficiency Tier 1 solar panels makes it more important than ever to get quotes from multiple solar installers. By getting more than one solar quote, you can compare various manufactures at different price points to make sure you’re getting the best solar system for your home - without breaking the bank. You can also use our solar panel calculator to get a personalized estimate of how much a solar installation would cost for your specific home, as well as see your projected savings over the lifespan of the solar panels. 

    High-efficiency solar panels to consider

    To help you with your solar panel buying decision, we’ve compiled a list of the best high-efficiency solar panels suitable for home use. 

    The high-efficiency solar panels below are offered by the best solar panel manufacturers - those with a review score of at least 4.5/5.0 and at least 20 reviews on SolarReviews. 

    We’ve only included solar panels that are designed for residential use, i.e. they are between 60 and 66 cells in size (or between 120 and 132-cells large where half-cell technology is used). 

    Manufacturer Model series Min efficiency Max efficiency Power output
    SunPower A-Series Residential 21.50% 22.80% 400 - 425 W
    SunPower X-Series X22 21.20% 22.70% 360 - 370 W
    LG Solar NeON R 20.80% 22.30% 360 - 440 W
    REC Group Alpha Pure 20.80% 21.90% 385 - 405 W
    LG Solar NeON R Ace - 21.80% 395 W
    REC Group Alpha X 20.60% 21.70% 360 - 380 W
    Panasonic EverVolt EVPV380 21.20% 21.70% 370 - 380 W
    LG Solar NeON R Prime 20.30% 21.50% 350 - 390 W
    REC Group Alpha Black 20.30% 21.40% 355 - 375 W
    Silfab Solar Elite 20.80% 21.40% 370 - 380 W
    Panasonic EverVolt Black 20.60% 21.20% 360 - 370 W
    JA Solar JAM60S20 19.60% 21.00% 365 - 390 W
    Seraphim S4 Series 20.17% 20.94% 390 - 405 W
    Canadian Solar HiKu Mono PERC 19.70% 20.90% 400 - 425 W
    Canadian Solar HiKu 19.50% 20.80% 360 - 385 W
    Q Cells Q.PEAK DUO BLK ML-G9+ 19.30% 20.60% 365 - 385 W
    Trina Solar Residential Module 19.20% 20.60% 355 - 380 W
    Seraphim S3 Series 19.76% 20.59% 360 - 375 W
    Axitec Solar USA AXIpremium XL HC BLK 19.76% 20.59% 360 - 375 W
    REC Group TwinPeak 4 19.70% 20.50% 360 - 375 W
    Canadian Solar HiDM 19% 20.50% 320 - 345 W
    Solaria PowerXT-300 19.90% 20.50% 360 - 370 W
    Seraphim S2 Series 19.67% 20.48% 365 - 380 W
    LG Solar NeON 2 20.10% 20.40% 365 - 370 W
    REC Group TwinPeak 4 Black 19.40% 20.30% 355 - 370 W
    Solaria PowerXT-400 - 20.20% 400 W
    Silfab Solar Prime - 20.20% 370 W

    Solar panel models listed as available in the U.S. as of June 15, 2021. 

    Several of the top solar panel manufacturers offer not just one, but many models of high efficiency solar panels. These tend to be their most expensive offerings, so unless you’re short on space, do also ask about the brand’s standard-efficiency solar panel models when you’re evaluating quotes.

    Calculate your solar panel payback period

    Key takeaways

    • Solar panel efficiency measures how much of the sunlight that hits a solar panel turns into usable electricity.
    • Most solar panels used today have efficiencies between 15% and 20%. SunPower’s Series A 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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