Solar Panel Efficiency

You may hear the term “efficiency” thrown around a lot when reading up on solar panels. It sure sounds like a good thing, but what exactly is solar panel efficiency? How is it measured?

We’ll go over some of the major factors contributing to the efficiency of solar panels, environmental factors that play a role, and some of the most efficient solar panels on the market today.

What is the efficiency of solar panels?

Solar panel efficiency is a measurement of how much of the sun’s energy a certain panel can convert into usable electricity. This is done by capturing the electrical current generated when sunshine interacts with the solar cells in the panel and is transferred through the wiring and busbars to be converted into AC (alternating current) energy. The AC energy is then sent to your Main Panel and distributed throughout the house. You can read more about how solar panels are manufactured in this post. 

Measuring efficiency is fairly simple. If a solar panel has 20 percent efficiency, that means it’s capable of converting 20 percent of the sunshine hitting it into electricity. The highest efficiency solar panels on the market today can reach almost 23 percent efficiency. The average efficiency of solar panels falls between the 17 to 19 percent efficiency range.

Factors that affect solar panel efficiency

Solar panels have been consistently increasing in efficiency at about .5% annually since 2010. Numerous scientific factors play into the solar cell efficiency equation. Three major components are

  • Panel material components
  • Reflectance efficiency
  • Thermodynamic efficiency

Monocrystalline vs. polycrystalline refers to the makeup of the solar cells in each type of panel. Monocrystalline refers to solar cells cut from a single source of silicon as opposed to polycrystalline solar cells which are made up of numerous silicon crystals melted together.

Monocrystalline panels tend to be more efficient due to their uniform composition. Additionally, they tend to achieve superior performance in less optimal conditions such as high heat and low light. Nearly all residential panels today are monocrystalline. Polycrystalline panels are typically less efficient due to their more fragmented composition. As a result, these panels tend to cost less than the more efficient monocrystalline panels. 

Reflectance efficiency is determined by how much sunlight is reflected back instead of absorbed and put to use. The less reflection in solar cells, the better. Glass, one of the most important components of a solar panel, reflects a very small portion of the light that falls on it. 

There are ways to reduce reflectance, such as anti-reflective coatings which nearly all solar panels on the market today utilize

Thermodynamic efficiency is the maximum efficiency possible. It’s the height at which the sun’s energy could be converted into electricity. This number is right around 86 percent, the thermodynamic efficiency limit.

The way photons interact with solar cells, they can only generate electricity from the sun’s energy up to a certain point. After that point (86 percent) thermal energy, or heat, is created.

One way to improve thermodynamic efficiency is to construct multi-junction or tandem solar cells. This improves efficiency by dividing the solar spectrum into smaller areas, which raises the efficiency limit for each section.

Top 5 Most Efficient Panels on the Market Today

Many panel manufacturers today are competing for the bragging rights as to the most efficient solar panel. Below is a list of 5 manufacturers bringing to market some of the highest efficiency residential solar panels in 2020:

SunPower, in addition to regularly setting and re-setting the bar for the single highest efficiency panel on the market, has also positioned themselves as the premium equipment manufacturer across the board. With multiple offerings above 20% efficiency, you always know you’re considering a top tier panel when shopping Sunpower. Checkout SunPower’s premium panel line.

LG, ever since breaking into the solar market, has been expected to deliver high quality products. And while they have certainly delivered on those expectations since the beginning, they have really raised the bar recently with their NeON 2 series and NeON R series which feature modules surpassing 21% efficiency. 

REC Founded in Norway in 1996, REC Group is the leading European brand for Solar panels and has been providing sustainable and high-performance products, services, and, investments for the solar industry for over 20 years. REC panels undergo stringent internal testing and third-party certifications, due to which the company touts that it has set the industry benchmark for quality. REC manufactures a wide array of panels, ranging in both efficiency and power. However, REC’s Alpha Series offers 5 panel options ranging from 360-380 W, all at above 20% efficiency and topping out at 21.7%. REC utilizes a unique, hybrid manufacturing technique referred to as heterojunction which combines crystalline and thin film material in order to deliver high density powered 60 cell panels. 

Solaria strives to differentiate themselves through cutting edge technology. Unlike most solar panels, Solaria panels have no busbars which help to avoid failure points and efficiency loss, parallel substrings to improve efficiency in less optimal conditions, and patented technology that cuts solar cells into overlapped strips which leads to a sleek and unmatched jetblack aesthetic. Check out Solaria’s advanced panel technology to learn more. 

Panasonic has a focus on quality over quantity. Since 1975, Panasonic has been at the forefront of research and development in the solar energy industry. It started with their work in amorphous solar cells, which are types of thin-film solar cells. Now, Panasonic’s solar offerings fall under the HIT trademark, featuring silicon heterojunction solar cell technology. With less residential panel offerings than other manufacturers, consumers can rest assured that any panel from Panasonic is going to score high on efficiency rating. Panasonic designs their panels via a unique pyramid structure, with bifacial cells and an innovative water drainage system; all to maximize efficiency. Whether it is their well known 330W panels at 19.7% efficiency or their newly released 340W panels at 20.3% efficiency, there’s never a question of quality when going Panasonic. 

Environmental Factors Affecting Solar Cell Efficiency

Shading from nearby buildings and trees are one of the biggest factors affecting solar panel efficiency. If you are dealing with shade from a nearby building, you may have the option of installing a solar canopy in order to reposition the panels to receive more direct sunlight. 

Tree’s can oftentimes be trimmed or even removed in order to increase the irradiance of a solar array. While removing a tree may seem counterintuitive to the positive environmental impact of installing solar, just remember that the CO2 offset your solar system will achieve will far exceed the carbon absorbing capability of that one tree! 

It is important when going Solar to ensure that whoever is designing your system is utilizing adequate software or other methods in order to accurately model and measure shading. Aurora, for example, is a premium modeling software that accurately takes into account all relevant environmental factors when designing a system. 

Solar Panel Efficiency is Affected by Environmental Factors

Significant amounts of dirt and dust can also reduce efficiency. For the most part, solar panels are self-cleaning. A rain shower can reset your panel efficiency in just a few minutes. If you live in a particularly arid region and heavy dust-storms are a problem, you might want to clean the panels off yourself. Here’s how to know if your panels need cleaning and how to go about it.

Snow is another area of confusion with solar panel efficiency. A thin layer of snow won’t hinder solar efficiency much. Read more about snow with solar, and solutions for heavy snowfall with solar here.

Efficiency’s Importance in Home Solar Solutions

Efficiency alone isn’t always the most important factor to consider when choosing the right panels for your project. You may not need the most efficient solar panels if you have enough roof space for less efficient, but more cost effective panels.

The direction your roof is facing, the slant, style, and area of your roof all weigh in on which panels might work best for you.

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