How Efficient Are Solar Panels?


If you have been researching solar panels, you have probably seen the term “solar panel efficiency” here and there. Although many articles and manufacturers mention solar panel efficiency, few take the time to explain what it is.

For this reason, we have created a comprehensive article about solar panel efficiency. In this article, we cover solar panel efficiency, how it is measured, and more. Read on to learn about solar panel efficiency.  

What Is Solar Panel Efficiency?

Solar panel efficiency measures a solar panel’s maximum ability to convert sunlight energy into usable electricity. In other words, solar panel efficiency measures how good a certain solar panel is at converting energy into electricity. The higher the solar panel efficiency, the more electricity that is produced.

When sunlight hits a solar panel, some of the light is reflected while the rest of the energy is captured by the panel and turned into an electrical current. That current is then transferred through wiring and busbars until it is finally converted into AC (alternating energy) energy, or usable energy. After AC energy is converted, it is sent to the Main Panel so that it can be used throughout your home or office.

Measuring Solar Panel Efficiency

Although this process may sound difficult, it is relatively easy to measure solar panel efficiency. Assume that a solar panel has 18% efficiency. This means that the solar panel can convert 18% of the sunlight energy into usable energy.

Today, the most efficient solar panel has about 23% efficiency. Most residential solar panels are between 17% and 19% efficiency.

What Factors Affect Solar Panel Efficiency?

Over the years, solar panels have become more and more efficient. In fact, solar panels have increased in efficiency by about 0.5% annually since 2010. The reason for this is primarily technological or material improvements.

Many factors, some technological and others not, go into a solar panel’s efficiency. The three most important factors are panel material components, reflectance efficiency, and thermodynamic efficiency. Let’s take a closer look at all three factors.  

Panel Materials

Solar panels can either be made from monocrystalline or polycrystalline cells. Both cell types are made from silicon, but the number of silicon cells differs.

Monocrystalline panels are solar cells cut from a single source of silicon. These panels are usually more efficient because of their composition. Additionally, these panels perform better in less-than-ideal environmental settings, such as high heat or low light. Most residential panels are monocrystalline.

In contrast, polycrystalline panels are solar cells that are made from many silicon crystals that have been melted together. Since these panels are more fragmented than monocrystalline panels, they tend to be less efficient.

Reflectance Efficiency

Whenever sunlight hits a solar panel, some sunlight is reflected back into the sky while other sunlight is absorbed by the panel. The more sunlight that is reflected, the less energy that the panel can convert into usable energy. Reflectance efficiency measures exactly how much sunlight is reflected.

Solar panels are made from glass, which is one of the best materials for absorbing light. Instead of reflecting a lot of light, glass is known for reflecting only a small amount of light. In addition to using glass, there are other ways to reduce panel reflectance, like anti-reflective coatings. 

Thermodynamic Efficiency

When the photons from the sunlight interact with the solar cells, the cells can only produce electricity from the energy up to a point, which happens to be 86%. Once that point is exceeded, thermal energy, or heat, is produced instead of electricity.

The highest point at which a solar panel can convert sunlight into electricity is called thermodynamic efficiency. So, 86% is the thermodynamic efficiency limit for solar panels. This limit measures the highest point of sunlight energy conversion.

There are ways that you can improve thermodynamic efficiency, though. Most notably, you can construct multi-junction or tandem solar cells, which divides the solar spectrum into smaller areas. These smaller areas raise the efficiency limit for each individual section.

Environmental Factors

Although environmental factors are not grouped into the three most important factors relating to solar panel efficiency, they should not be ignored. From a cloudy day to a growing tree, solar panel efficiency can be greatly reduced by environmental factors.

In most areas, shade from nearby buildings and trees are the biggest environmental culprits for reduced solar panel efficiency. If you live in an area surrounded by buildings, you will want to position your solar panels so that they are best avoiding the shade. Similarly, you should trim or remove trees that are shading your solar panels.

Other environmental factors include:

  • Weather
  • Clouds
  • Sunlight exposure

Why Does Solar Panel Efficiency Matter?

Solar panel efficiency matters for two reasons: size and cost.

Firstly, the more efficient a solar panel is, the fewer panels you need to support your electricity needs. As a result, homes with more efficient solar panels need fewer panels, which results in less bulky panels covering your roof or yard.

Secondly, more efficient solar panels will save you money. Since high-efficiency solar panels produce more electricity, they will decrease your need for grid electricity and maybe even cause you to have a surplus that you sell to your local utility.

5 Most Efficient Panels On The Market

Since solar panel efficiency increases every year, manufacturers constantly compete for the most efficient solar panel on the market. Here are the 5 manufacturers that currently produce the most efficient solar panels:

  1. SunPower

    SunPower consistently produces some of the most efficient solar panels, and they have even been able to brand themselves as the best premium equipment manufacturer. This manufacturer has multiple solar panel options that are about 20% efficient, proving that SunPower produces some of the best solar panels.
  2. LG

    LG only started selling solar panels in 2010, but they have been producing some of the best models since then. Their NeON 2 series and NeOn R series are especially impressive with models that surpass 21% efficiency.
  3. REC

    REC is a leading European solar panel manufacturer. Founded in Norway in 1996, this company has been offering sustainable and ecofriendly services, products, and investments for the solar industry for just over two decades. Before being produced and sold, all REC solar panels are subjected to rigorous internal testing and third-party certifications to ensure that their solar panels are of superior quality. Because of these tests, REC views itself as a trend-setter in terms of solar panel quality.

    Many of REC’s solar panels have superior power and efficiency. Notably, the Alpha Series includes 5 panel options that all surpass 20% efficiency. REC’s unique technique called heterojunction is the reason for the panels’ efficiency. In short, heterojunction combines crystalline and thin film materials to create high-density panels.

    Solaria focuses on technology to create highly efficient solar panels. Unlike other panels, Solaria panels lack busbars, which avoids failure points and reduced efficiency. Instead, Solaria uses patented technology that allows solar cells to be cut and placed as overlapping strings. These strings create a sleek look that produces high-efficiency.

Panasonic has been in the solar industry since 1975, making it a leader in solar energy research and development. Since its early beginnings, Panasonic has focused on quality over quantity, resulting in some of the most efficient solar panels on the market. Originally, Panasonic worked with amorphous solar cells, and today all their solar offerings come with a HIT trademark, which includes a silicon heterojunction solar cell technology.

In comparison to the other leading manufacturers, Panasonic produces fewer solar panels for residential use, but all their panels have high-efficiency ratings. Because of their unique pyramid structure, bifacial cells, and innovative water drainage system, Panasonic solar panels consistently have around 20% efficiency.

Final Thoughts

Solar panel efficiency is one of the best ways to measure a solar panel’s performance and capabilities because it tells you exactly how much sunlight energy your solar panel converts into electricity. The higher a solar panel’s efficiency rating, the more efficient your solar panel is at converting energy.

Although solar panel efficiency is important, solar panel efficiency is not the most important factor when selecting a solar panel for your home. There may be other factors that are more important to your decision than solar panel efficiency. For example, you might want to opt for less efficient panels if you have a lot of roof space and are on a tight budget.

Factors such as the direction of your roof, the slant, style, and location of your roof will be more important when selecting the right solar panels for you. The reason for this is that you need to maximize exposure to the sun for the solar panels to even utilize their efficiency in the first place.

With this in mind, solar panel efficiency is important to consider, but it might not be the main priority for your panels. Nevertheless, you should select panels with the highest efficient ratings that match your other needs as well.


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