Longi Solar Panels - Review

Longi Solar is a Chinese company that is a tier one manufacturer of solar panels.  They only produce monosilicon panels and may be the largest monosilicon solar panel manufacturer globally.  Their panels come with a 10 year product warranty. Longi Solar's Australian office can be reached for warranty support or assistance on 02 8484 5806.

Longi Solar Panel Production

Longi Solar was the world's fastest growing solar manufacturer in 2016 and has continued to grow rapidly since.

In 2019, it shipped 7.394 GW of cells and modules, an increase of 23.43% over 2018. By the end of 2019, Longi reached 42GW of monocrystalline silicon wafer and 14 GW of mono panel production capabilities.

Longi is a member of the "Silicon Module Super League";  which a small group of companies that account for the majority of the world's solar panel production.

Most of the company's production had been used in China, but the firm has been expanding into overseas markets and Longi solar panels are becoming a more common sight on rooftops in Australia. In 2019, its overseas shipments grew 154.59% year over year.

Company History

Founded in 2000, by 2007 Longi boasted 100 tonnes of monosilicon production capacity - enough for approximately one gigawatt of solar panels these day. In 2007, it was likely less, as silicon ingots were still being cut into the thicker "toast" slices instead of the thinner "sandwich" type silicon ingot loafs they do today. These days, ingots are cut so thin, there's only approximately half a gram of silicon in each solar cell.

Longi shipped 2.5 gigawatts of silicon wafers in 2014, which are slices of silicon ingot before they are turned into solar cells.  2014 was also the year Longi stopped producing silicon ingots and wafers exclusively and expanding into solar panel manufacturing by buying Lerri Solar.

After acquiring Lerri Solar, which had been making solar panels since 2007, Longi continued to produce panels under the Lerri name until early in 2017 when the company rebranded as Longi Solar.  Longi may have held off on the rebranding to ensure solar panel reliability was up to par before associating the Longi name so closely with them.

From 2014 to 2016 Longi expanded rapidly.  Fortunately this success did not lead to them becoming arrogant and developing a Longi 'tude. 

Longi Headquarters

Longi is headquarted in Xian, or Xi'an; which located in Shaanxi Province, but Longi says on its website this city is located in the neighboring Shanxi Province.  Somehow the company confused Shaanxi and Shanxi when writing about themselves in a foreign language.  I can't imagine how that happened.

Longi is headquartered in Xi'an rather than further south near Shanghai where the majority of the world's solar panels are made because they began operations as a silicon manufacturer.  Monosilicon production requires a great deal of electrical energy, so they were founded in an area with access to cheap coal power.  Fortunately, China is taking steps to reduce their coal use and one of them is a massive build out of solar capacity. In March 2020, Longi committed to sourcing 100% renewables-based electricity across all its operations by 2028.

Local And Overseas Production

Longi has 9 factories in China, spread across Shaanxi, Jiangsu, Zhejiang, Ningxia and Yunnan.

In addition to their Chinese factories, Longi expanded production overseas.  Longi constructed a factory in India with the ability of manufacturing 500 megawatts of solar panels annually.  The facilility is situated in the Special Economic Zone (SEZ) in Sri City in Andhra Pradesh.  The factory employs 1,000 people, which is a significant number for a 500 megawatt plant these days, but as wages are lower in India compared to China, it's not unusual to be hiring more staff than they would back on their home turf.

Longi has also purchased a facility in Malaysia capable of 500 MW of solar panel capacity a year . The plant will ship in silicon ingots, slice them into wafers, produce solar cells and panels, and then melt all the waste silicon to produce new ingots on site.

Longi Makes Monosilicon Exclusively - No Polysilicon

There are two types of silicon used in the production of solar cells -- polysilicon and monosilicon.

Polysilicon is comparatively easy to make.  The molten silicon is poured into a mold and allowed to cool.  It's quick, easy, and there's little in the way of waste.  Its disadvantage however, is it is made up of multiple crystals of silicon; which impacts on the efficiency of solar cells.

Monosilicon is significantly more difficult to produce and consequently more expensive, but the process results in a single large crystal of silicon, enabling solar cells be more efficient.

Longi only makes monosilicon and is the world's largest producer -- at least in respect to ingots.  They own a massive number of specialised slow cookers called crucibles that bake and rotate at the optimum rate to produce cylindrical ingots of silicon using the Czochralski process.  Ingots used for solar cell production are typically 10 to 20 centimeters across.

The crucibles, which reach temperatures of 1,425 degrees Celcius, are usually made from quartz which has a melting point of 1,713 degrees Celsius.

Longi's Vertical Integration

As Longi produces silicon ingots, wafers, solar cells and solar panels, they are considered a vertically integrated company.  While this provides the company a secure supply of silicon, there is potential that by making the company larger, it becomes more cumbersome and less able to react to sudden changes in solar technology and the market.

Monosilicon = Efficient Panels

As monosilicon enables panels to be more efficient in converting sunlight to electricity than polysilicon, Longi Solar panels have reasonably high efficiencies. Their 60 cell panels, which are likely to be used on Australian rooftops, have efficiencies ranging from 17.4% to 20.3%.

Longi is a participant in China's Top Runner Program, which is a government scheme with a goal of boosting the efficiency of Chinese solar panels.

Multiple Records Set

Longi has achieved a number of records for solar cell efficiency in the last few years, and this drive to achieve recognition for its research and development efforts is something that benefits us all. As one manufacturer sets a record, another breaks it - and the cycle goes on. While these are often just incremental improvements, these added up make for significant progress.

Risk Of A Monosilicon-Only Approach

With a sole focus on monosilicon and owning so many dedicated monosilicon crucibles means Longi is potentially running the risk being saddled with a great deal of outdated expensive equipment if there are significant declines in the cost of silicon production using other methods.  However, as solar production is expanding very, very quickly; even if more economical methods do appear, old and new technologies could coexist for a significant period.

Longi Performance Warranty - Better Than Average

Most tier one solar panels at the lower end of the pricing range only guarantee around 80% of their originally rated power after 25 years.  But Longi promises their standard panels will still produce at least 83.1% of their original output after this time and their PERC panels will provide at 84.8%. 

With a little luck, other lower cost tier one panel manufactuers will feel confident enough in their engineering to bump up their performance warranties to being them in line with Longi's.

Warranty Procedure For Orphaned Longi Customers

If you have purchased Longi solar panels from a solar installer who has since gone out of business, the responsibility for warranty claims shifts to Longi as the manufacturer. Their Australian office can be reached on 02 8484 5806 - affected customers should contact this line for assistance. Longi have advised that customers will be asked to send through photos and serial numbers of affected panels to an email address that they will provide, and they will then arrange for the replacement of the panels. If required, Longi will be able to recommend installers to carry out the work if a customer is unable to organise one themselves. They will also reimburse customers for labor costs involved with replacing the panels.


Longi solar panels are tier one and so should be reliable and I would not have a problem with installing them on my roof.  They will also appeal to people who are interested in panels that should lose little in capacity over the years, but don't want the expense of purchasing premium panels.

While many companies have run into financial difficulties after rapidly expanding, Longi's financial position appears reasonably sound.  While I don't have any solid evidence, I suspect they will be around for a longi time.  I can feel it in my gut.  Specifically, my longi intestine.

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