Longi solar panels review

Longi sells 'standard' solar panel setups for flat and pitched roofs, as well as 'custom solutions' for more complex roofs (such as villas, roofs with skylights or complicated layouts). 

Based in Yunnan, China, it says that its mission is to 'make the best of solar energy to build a green world'. We’ve tested solar panels from Longi and found out more about the company to help you work out if these are the right solar panels for your home.

You can also head to our guide to solar panel brands compared to see more of the options available.

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Longi solar panels reviewed

Longi reliability and warranty

Notes: based on the most efficient panel we've recently tested.

Where are Longi solar panels made?

Longi's main manufacturing facilities are based across China. It also has factories in Kuching, Malaysia and in Vietnam.

Longi solar panel test results

We've tested three Longi solar panels to see how they fare in typical UK conditions.

Our independent tests let us assess how the panels compare to the claimed stated performance when new, and following solar exposure. Our tests also reveal how much the panels degrade as they age.

Compare tech specs for the JA Solar solar panels we've tested in the table - scroll down to see how each panel performed in our detailed lab tests.

The UK solar panel market is fast moving and panels don’t tend to stay around for too long as the technology updates. For that reason, we don’t award Best Buys for specific models. Instead, we use our results to give you an overall steer on how a particular brand compares.  

Only Which? members can access our solar panel lab results. Log in now to see how Longi's panels fared.

Or join Which? to get instant access to the solar panel test results for the three panels we’ve tested and our expert verdict on the Longi brand.

Visit the Longi website to view the options available for your home.

Longi solar panel owners' opinions

When we surveyed solar panel owners*, many with Longi solar panels told us that they have produced more electricity than they expected, including on cloudy days.

Several like the look of their solar panels, including their 'simple, plain-black appearance' and that they're 'neat-looking'.

Nearly half of those who owned Longi solar panels in our survey said they'd chosen them as the only brand fitted by their chosen installer. But 10% also chose it from a choice of brands offered by their installer or based on price.

The majority told us that there was nothing they disliked about ther Longi solar panels.

Our solar panel tests explained

We started testing solar panels in 2026. 

Testing solar panels is complex and takes a lot of time, not least as the testing requires plenty of hours of sunlight. We’ve teamed up with our European Consumer colleagues to test panels in a specialist facility in Spain that’s been testing solar panels for decades. We test each panel according to the standards that regulate and control these products. 

We know that solar panels will perform differently in the UK than in Spain. So rather than simply using the Spanish test results as they come, where applicable we model the results to daylight conditions across a number of UK cities to see how they would perform in UK homes.

Each panel is inspected for defects before testing and installed using specific tilt angles and orientations for direct sunlight exposure that’s directly comparable across all panels we test.

Once installed we run a series of tests. These include an initial solar radiation exposure; a maximum power determination test; an outdoor exposure test and a test to check for any current leakage in wet conditions. Special images are taken to detect minute defects and cracks created during the initial test programme. We then repeat the tests to work out how much the panel's performance degrades over time and if the defects affect ongoing performance.

Find out more about how we test solar panels.

How to buy Longi solar panels

As a domestic customer, you’ll need to buy solar panels through an installation company. In a January 2026 survey** of solar panel owners, nearly half told us they used an independent solar panel installer, while 25% used a larger solar panel company for their work.

Most installers will only work with one or two brands; almost three quarters of the solar panel owners in our survey only had one brand of panel offered by their chosen installer, while 14% had a choice between two brands. It’s worth getting a few quotes from different installers so that you can compare what brands are being offered, as well as comparing the installers themselves. 

Trying to compare solar panel installers? Our guide to how to choose a solar panel installer will help you ask the right questions.

* Data based on a April 2024 online survey of more than 2,000 Which? members who have solar panels on their home. 

**Data based on a January 2026 online Combo survey of 948 solar panel owners who had them installed in the last three years.