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Solar Panel Efficiency: The Best Brands and Scores

house with sunpower solar panels - solar panel efficiency

Solar Panel Efficiency

Residential solar panels have dramatically increased in efficiency and decreased in cost over the past decade, thanks to improvements in the manufacturing process and further research and development. If you’re someone who plans to invest in solar panels for your home in the future, I’m sure you’re very interested in how to get the most bang for your buck.

What are the different factors that go into giving a solar panel efficiency, and what makes certain solar panels more efficient for your home? These are the questions we will be taking a look at below.

Lets dive in...

What Determines the Efficiency of a Solar Panel?

The efficiency of a solar panel is simply determined by how much energy one solar panel cell is able to convert from the sun. In the form of an equation, how much energy a solar panel can create from the sun is determined by dividing the amount of electricity the solar panel can produce in watts and the amount of energy it absorbs from the sun.

How do Solar Panels Work and How is its Efficiency Tested?

When the sun hits the silicon or thin film inside of a solar panel, the electrical current that is generated is measured to determine the amount of usable electricity produced. The tightly packed solar cells lay within glass rectangles for optimal sunlight attraction. They gather energy from the sun and send it to your circuit breaker box to feed electricity into your home.

The standard temperature for this evaluation is typically 77 degrees Fahrenheit (25 degrees Celsius), with 1000 watts of sunlight per square meter actively striking the panel.

To simplify it, if a solar panel has an efficiency of 30 percent, it will be able to convert 30 percent of the sunshine it attracts into electricity.

Comparing two different solar panels, if the same amount of sunlight is shining on them for the same duration of time, whichever panel produces more electricity is the more efficient one. "In practical terms, for two solar panels of the same physical size, if one has a 21% efficiency rating and the other has a 14% efficiency rating, the 21% efficient panel will produce 50% more kilowatt hours (kWh) of electricity.”

What is the Average Efficiency of a Solar Panel?

Although the most efficient solar panel being manufactured today can be over 40% efficient at converting sunlight into electricity, these expensive panels are usually not on residential homes, but rather on satellites.

Currently, the highest efficiency rating for residential solar panels is at around 20% typically topping off at just about 23%. However, the average efficiency of today's solar panels is 15 to 18 percent.

There are several leading residential solar panel companies paving the way for higher efficiency levels in solar power, with the top three being SunPower, Panasonic, and LG. Climbing the charts at a little above 20%, The SunPower solar panels currently hold the record, as of March 2018, reaching an average efficiency of 21.5%, even producing 22.8 percent in production.

What are the Best Types of Solar Panels for Efficiency?

For the majority of residential roofs, the solar module material that is used is made out of crystalline silicon. Monocrystalline silicon is the most efficient, as of March 2018, with polycrystalline cells close behind.

Monocrystalline silicon solar cells are able to produce higher levels of electricity for longer, which allows SunPower to have a 25-year output warranty on their solar panels. This high efficiency also makes monocrystalline panels more expensive than polycrystalline silicon panels to manufacture.

Factors that Contribute to your Solar Panel Efficiency

The efficiency of a solar panel is not just measured by the energy output it produces when interacting with sunlight. Overall efficiency is better understood by looking at a solar panel's ability to convert sunlight into energy at a low cost and high supply rate.

Two big factors that contribute to how efficient a solar panel is are its reflectance efficiency and its thermodynamic efficiency.

Reflectance Efficiency:

This is determined by how much sunlight the panel absorbs for use as opposed to how much sunlight it reflects. The less sunlight a solar cell reflects, the more electricity it is producing. The reflectance of silicon can be as high as 38 percent, however, most solar cells implement a micro pyramid shape, which reduces its reflectance to about 11 percent.

Additional things can be done in the manufacturing process to reduce reflectivity. One of these things involves adding anti-reflective coatings to the solar cells. Another advanced solar cell construction method stacks micro and nano-sized arrays on top of the larger components. This can lower reflectance down to 1 or 2 percent.

Thermodynamic Efficiency:

This describes the solar panel maximum possible efficiency. It is the highest percentage at which the solar cells are able to convert the sun's energy into electricity. This number falls at around 86 percent, which is called the thermodynamic efficiency limit.

The number does not go above 86 percent because of the way photons interact with solar cells. They are only able to generate electricity from sunlight to this maximum, at which point, thermal energy, or heat, is created.

If you're looking to improve the thermodynamic efficiency of your solar panels, you can construct multi-junction or tandem solar cells. This serves to divide the solar spectrum into smaller areas, raising the efficiency limit.

How to Optimize Solar Panel Efficiency for your Home

One size does not necessarily fit all when it comes to choosing the best solar panel system for your rooftop. You may want to maximize the amount of electricity your entire solar panel system can deliver, or you may want to avoid getting a system that produces more energy than your home needs. But you only have a limited amount of roof space available. In either case, it is best to opt for higher efficiency panels to get the maximum production for your particular system.

Another often overlooked, but equally important part of a solar panel overall efficiency is its watt ratings, which refers to how much power the PV (Photovoltaic System) panel creates.

For example, the Sunpower panel produces 370 watts, while the LG panel comes out at 330 watts, and the Panasonic N330 Photovoltaic Module HIT can produce 330 watts. The higher the wattage rating, the more power output there is per panel.

top 3 high efficiency solar panels comparison graph

How Many Solar Panels Would Your Roof Need?

Possibly the greatest benefit that comes with having a more efficient solar panel is the fact that they require less overall space to generate more power. Comparing various solar panel manufacturer brands, depending on the size of your roof and how much electricity you are going to need, you will require more or less solar panels.

This means if you are using SunPower's highest efficiency rated panels for a 5-kilowatt solar system, you would need 15 SunPower 41 by 61-inch panels, which would use about 261 square feet of your roof space. On the other hand, if you were to install LG panels, which are a litter bigger in size, at 40 by 67 inches, 15 of the panels would take up 279 square feet.

Most efficient Solar Panels of 2018

  1. Manufacturer: SunPower X Series; Model: SPR-X21-345; Efficiency Rating: 21.5%

  2. Manufacturer: LG Solar; Model: High NeOn R Module; Rated Efficiency: 21.1%

  3. Manufacturer: Panasonic HIT Panels; Model: N330 HIT; Efficiency Rating: 19.7%

  4. Manufacturer: Sunpreme; Model: GxB 380 SM Bifacial Smart Module; Rated Efficiency: 19.5%

  5. Manufacturer: Upsolar; Model: UP-M315M; Rated Efficiency: 19.4%

  6. Manufacturer: Trina Solar; Model: Tallmax M Plus; Rated Efficiency: 19.3%

  7. Manufacturer: Winaico; Model: WSP-M6 PERC; Efficiency Rating: 18.9%

  8. Manufacturer: Itek Energy; Model: Itek SE 60-Cell Module; Rated Efficiency: 18.8%

  9. Manufacturer: Mitsubishi Electric; D6M 360 E4A; Rated Efficiency: 18.6%

  10. Manufacturer: Recom; Model: Black Panther; Rated Efficiency: 18.6%

  11. Seraphim; SRP-6MA; Rated Efficiency: 18.6%

  12. Phono Solar Technology; PS300M-20/U; Rated Efficiency: 18.4%

  13. Canadian Solar; CS 6K-300MS; 18.3%

  14. SolarWorld Americas; Sunmodule SWA 340 - 350 XL MONO; Rated Efficiency: 17.5%

  15. Kyocera Solar; KU320-7ZPA; Rated Efficiency: 16% (Kyocera does not include efficiency ratings on their spec sheets. However, they say that their solar cell's efficiency is over 16%).

Environmental Factors Affect on Solar Panel Efficiency

Although solar panels are more resilient to natural outdoor interruptions than most people would think, there are a couple environmental factors that can sometimes hinder your panels ability to generate its optimal level of electricity generation from the sun.

These include:

- Heavy shade cast by buildings, trees, or large clouds.

- Significant amounts of dust, dirt, or debris

A great thing about solar panels is that they are usually good at self-cleaning, so the above-mentioned circumstances are only temporary hindrances. A good rainfall can quickly help to wash away any blockages, getting your solar panels back up to maximum efficiency. Heavy dust storms are an exception, where you may want to clean off your panels by hand.

Winter is actually the best season for solar power. Since most electronics operate better when running cooler, solar panels are no exception. Also, given that solar panels run on sunlight, as opposed to heat from the sun, the brightness of a winter day can be a solar cell's best friend. Light snowfalls are not an issue for solar panels to keep working correctly, however, heavy layers of snow can put a halt on sunlight absorption.

What is The Takeaway?

More and more people are using residential solar power systems for their homes, which is probably a direct correlation to the increase in its efficiency, with the highest rated residential solar panel from SunPower being rated at just under 23%.

Both the wattage rating and the efficiency rating of a solar panel are important determinants of how well a solar panel will work, and getting the most out of your solar panels depends on their ratio of sunlight absorption to reflection.

Homes with less roof space will gain the most electricity from solar panels that are more efficient.

Very few environmental elements, aside from a natural disaster, can damage or stop solar cells from working for long, because solar panels are self-cleaning the majority of the time. Lastly, knowing the direction your roof faces, how it slants, its area, and even its style, can help you pick the most efficient solar power panels for you.

If you’re considering solar and you live in San Joaquin County, Hayward, Tracy, Oakdale, Concord, Walnut Creek, Union City, Discovery Bay or any of the surrounding areas - give us a call for a free local quote.




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