Updated 4 weeks ago

Expert review of LONGi solar panels

Written by Ana Almerini

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LONGi Solar was founded in 2000 and is based in China, but they have offices all over the world with a headquarters in the U.S. LONGi has been in the solar photovoltaic business for over 20 years, which is important as you can trust that they will be in business over the lifetime of your panels.

Additionally, LONGi was among the 10 best solar panels of 2024 according to our experts! Our list was compiled based on numerous factors, most notably the financial strength of the company, length of business, and customer reviews. 

We will break down the types of LONGi solar panels available, discuss what makes them unique, what you can expect in a warranty from LONGi, and more.

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Key takeaways

  • LONGi Solar is one of SolarReviews' top-ranked solar panel manufacturers.

  • LONGi offers 3 types of solar panels for residential use, ranging from 355 W - 425 W.

  • LONGi solar panels cost about $2.40 per watt, which is lower than the U.S. average of $3.00, making LONGi panels a cost-effective choice.

  • With a competitive warranty and a proven reputation, LONGi solar panels deserve a spot on your roof.

What makes LONGi Solar stand out?

LONGi Solar, a Tier 1 solar panel brand, offers state-of-the-art solar technology features in their solar modules, including PERC technology

PERC cells allow solar panels to have a high cell efficiency. PERC, or “passivated emitter and rear contact” panels, have an extra layer of glass on the backsheet of the solar cells that helps reduce energy loss and turns more of the sun’s rays into electricity.

All of the LONGi Solar panels are also half-cut cell modules, which further increases their efficiency.

What solar panel modules does LONGi offer?

LONGi offers four main module series, the Hi-MO 7, Hi-MO X6, Hi-MO 5, and Hi-MO 5m -- but only the Hi-MO 5m Series offers panels for residential use

Bifacial solar panels are not practical for residential installations but have gained popularity in commercial applications over the past few years.

There are three models to choose from in the Hi-MO 4 Series, with varying wattage and other features.

A few things to keep in mind when reviewing solar modules: a high efficiency for a solar panel is anything above 21%, with 20% still being excellent. Additionally, the wattage of solar panels generally ranges from 370 W to 400 W per panel in ideal conditions. 

Hi-MO 5m Monofacial Modules 

The Hi-MO 5m Monofacial Modules feature both half-cut and PERC cells, with two model options to choose from.





405 - 425 W

20.7% - 21.8%


525 - 565 W

21.1% - 21.9%

Based on the above specs, you can see that the modules offered have high wattages and efficiency. High wattage and high-efficiency panels do a great job of creating electricity from the sun. 

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

The higher the efficiency, the more electricity the panels can convert into electricity. So, if you have limited roof space, you’ll want to choose the panels that are the most efficient so you can maximize the amount of energy you can produce. 

With that said, the 405 - 425 W panels should fit the typical roof -- any panels much bigger than that are more commonly seen in large-scale solar projects. 

How much do LONGi solar panels cost?

While you can find pricing to buy panels from a supplier, pinpointing the exact cost of solar panel installations is challenging. Many factors go into the total cost, from installation costs to shipping costs. But as a ballpark estimate, LONGi solar panels cost about $2.40 per watt

As of 2023, the average cost per watt for solar panels is $3.00, making LONGi solar panels a cost-effective choice. If you consider an average 7 kW size solar system, a LONGi solar system will cost about $16,800 before the federal solar tax credit. After the tax credit, the cost would drop to around $11,760; overall - a very practical price for solar panels (especially with such high-efficiency ratings).

How well do LONGi solar panels perform?

Because LONGi solar panels use half-cut cells, they perform well in most conditions. Half-cut cell technology allows the panels to essentially operate as two separate panels on the top and bottom, so if one half is shaded or damaged, the other half will be unaffected and continue to supply power.

Another important factor to consider is the temperature coefficient, which is how much the performance of the panels decreases with each increasing degree in temperature. Because solar panels are a dark color, they absorb a lot of heat which makes them hotter than the outside temperature. The hotter it gets, the less power solar panels can produce. 

What this all means is, the lower the temperature coefficient, the better. A higher temperature coefficient means that more energy is lost when the solar panels get hotter.

All of the Hi-MO 4 Series modules have the same temperature coefficient of .048% which is unfortunately on the high end, considering most modules have a temperature coefficient between .3% -.5%. 

How does LONGi Solar’s warranty stack up to the competition?

LONGi Solar offers a 12-year limited product warranty for workmanship and defects and a 25-year performance warranty. The product warranty does not cover normal wear and tear or changes caused by normal use of the system: the modules must be installed and used as they are designed to be.

As for the performance warranty, also known as the power output warranty, LONGi covers the panels for 25 years. At the end of 25 years, LONGi guarantees that the annual output of the solar panels will be at least 84.8% of their original solar energy output at the time of installation. With most solar panel companies, the range is about 80%-90% of the original output, so this number falls in line with the industry average. 

Most high-end solar panel manufacturers offer a 25-year warranty for performance and product, LONGi only offers a 12-year product warranty. 

Are LONGi solar panels right for you?

LONGi solar panels are a great choice. No wonder why they landed the number six spot on our top 10 solar manufacturers list for 2024. LONGi is a reputable solar module manufacturer with high-quality panels and with a solid review score of 4 out of 5 on SolarReviews

Two downsides of LONGi solar panels include their high temperature coefficient and the less-than-impressive product warranty, but it’s ultimately up to you to decide whether or not these (somewhat minor) factors are a dealbreaker. 

Working with local installers is the best way to ensure that you get the best panels for your specific needs - at the best price. 

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Written by Ana Almerini Marketing & Communications Manager

Ana is the Marketing & Communications Manager at SolarReviews, working within the solar industry since 2020. With a Master's in Climate and Society and professional experience in marketing, she helps communicate the value of solar to homeowners and build awareness of the SolarReviews brand. On weekends you can find her at the Jersey shore, reading a book from the ever-increasing stack on her side table, or eating food someone else cooked....

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