Longi Solar Panels Review UK

If you have three solar quotes in the UK, there’s a fair chance one of them uses Longi panels. This Longi solar panels review covers which models you’ll actually be offered, what their datasheets promise and where the warranty stops helping you.

Longi tied with JinkoSolar at the top of InfoLink’s 2025 module shipment ranking, at 80 to 90 GW each, so the name itself isn’t a risk. The risk is vagueness. A line reading “Longi 420W” could be a modern back-contact panel or an older PERC one, and the two age very differently.

Which Longi model is on your quote?

Five Hi-MO names matter, but only three are made for houses. The cell technology counts for more than the wattage, because it sets degradation, temperature behaviour and warranty length.

Datasheet figures for the models named. Your exact model code decides the real numbers, so ask for the datasheet. Sources: X10 datasheet listing, Longi’s Hi-MO 6 briefing, Longi’s Hi-MO 7 page and PV Tech on Hi-MO 9.

Reading a Longi model code

A code such as LR7-54HVH-485M splits into the platform (LR7), the cell count (54, the standard domestic format), a letter block for cell type and variant, and the rated watts. LR5-54HPH-420M is a Hi-MO 5, LR5-54HTH-445M is a Hi-MO 6 and LR7-54HVH-485M is a Hi-MO X10. Longi also sells most models in trims such as Explorer and Scientist, with different backsheets and sometimes longer product warranties. Write the full code on the quote, not the trim name.

On Hi-MO 5: we’ve argued that new P-type PERC quotes deserve a challenge, and Longi’s own development has moved to back-contact cells. Old PERC stock is fine as genuinely cheap clearance on a tight budget. It isn’t fine at n-type prices.

The back-contact look is a real selling point on a visible roof slope. Hi-MO 6 and X10 have no silver gridlines on the front, which is why many installers quote them over a marginally cheaper TOPCon panel.

Hi-MO X10 or Hi-MO 6?

For most roofs we’d pick the X10. It uses the newer HPBC 2.0 cell, has the better temperature coefficient and the longer power warranty, and packs more power into each square metre.

Power per square metre is our own arithmetic from rated power and panel size.

On 20 m² of usable roof that works out at roughly 4.8 kWp of X10, 4.6 kWp of Hi-MO 6 and 4.3 kWp of a 420W Hi-MO 5, before allowing for spacing and roof edges. Choose the Hi-MO 6 if the installer’s price per watt is clearly lower or if the shorter panel fits your layout better. The X10 is 78 mm longer, which can matter around chimneys and roof windows.

How Longi panels perform in UK conditions

British solar works in cool, dull, diffuse light, so the figures worth holding an installer to are the temperature coefficient and degradation, not the peak wattage on the label.

Hi-MO 6 first-year and annual rates are implied by its 88.9% year-25 guarantee, and the X10’s year-25 figure is worked out from its 99% start and 0.35% annual step. Trims vary, so check your datasheet.

Cool weather flatters every panel, so we wouldn’t pay extra mainly for a better temperature coefficient. Degradation is different because it compounds for decades, and it’s the clearest reason to prefer an X10 or Hi-MO 6 over old PERC stock. Longi says back-contact cells cope better with weak light, but we haven’t seen independent UK field data that proves a meaningful gain, so we’d hold installers to the degradation and warranty lines. For the wider picture, see whether solar still pays in British cloud and how panels behave in a heatwave.

Longi solar panel warranty: what it covers and what it doesn’t

Every Longi module has two warranties running side by side. The product warranty covers manufacturing defects such as delamination, junction box failure and frame faults. The linear power warranty guarantees a minimum percentage of rated output at the end of its term, falling at a published annual rate.

Datasheet typicals. The datasheet for your exact model code is the only version that counts.

The wording matters more than the headline years. In the Longi limited-warranty text we read (versions differ by region and model, so check yours), the usual limits are these:

• The remedy is repair or replacement, not a payout for lost generation.
• Labour, removal and reinstallation costs are excluded, so a claim can still cost you scaffolding and installer time.
• Damage from poor installation, misuse, lightning, fire or flood isn’t covered. Storms belong to your buildings insurance.
• Serial number labels must stay legible, and Longi may ask for independent testing before accepting a fault.

Longi’s wording sends claims to the supplier or its authorised distributors. On a UK roof that normally means your installer deals with the distributor, so our advice in the full guide to what solar warranties cover holds: go to your installer first. The warranty can pass to a later owner if the panels stay where they were installed, so keep the invoice and serial numbers for when you sell a house with solar panels.

Then ask who stands behind the installer. MCS is replacing the old two-year insurance-backed minimum with at least six years of cover, and installers have until 31 March 2027 to switch. If your installer disappears mid-claim, warranty insurance and our notes on a solar installer going bust explain your options.

Price and value: what Longi costs in the UK

The Hi-MO X10 typically costs about £75 to £100 per panel before installer markup and labour, which is roughly 15p to 21p per watt for the panel alone. That’s mid-market. On a ten-panel array, our own comparison puts the premium of Longi over JA Solar at about £50 to £150, against £200 to £400 for AIKO over JA Solar.

Panel price is a small slice of the bill. MCS data puts the English average at about £1,591 per kW fully installed (March 2026), and a 4kWp system lands at roughly £5,500 to £7,500. Our UK solar cost guide and the analysis of what MCS data shows about £10k 4kW quotes give the benchmarks, and price per watt is the only fair way to compare quotes of different sizes.

Two policy points apply whichever brand you choose. Domestic solar and battery installs carry 0% VAT until 31 March 2027, and the rate is due to return to 5% after that. And you only earn export income under the Smart Export Guarantee if the install is MCS-certified. Our payback guide and SEG rate comparison run the numbers for your roof.

Longi as a company: bankable, with caveats

A warranty is only as good as the balance sheet behind it. Longi was founded in 2000 in Xi’an, is listed in Shanghai and, per InfoLink, shipped as many modules in 2025 as any manufacturer. Its own 2025 results show revenue of CNY 70.3 billion and 22.87 GW of HPBC 2.0 back-contact module sales, the technology behind the X10.

The same report shows a net loss for the year, narrowed by CNY 2.17 billion on 2024, which was also a loss-making year. That comes from the industry-wide price war, and it doesn’t change how a panel performs on your roof. It does mean you shouldn’t rely on a manufacturer’s promise alone for 30 years, which is why the installer relationship, the MCS paperwork and optionally warranty insurance matter.

Longi is a Chinese manufacturer, like most of the sector: China holds more than 80% of global solar manufacturing capacity. If supply chains weigh on your decision, read our pieces on why 68% of Britain’s solar panels come from China and forced-labour scrutiny in the solar supply chain.

The quote checklist: buying Longi without the guesswork

• Get the full model code in writing, for example LR7-54HVH-485M. “Longi 420W” is not a specification.
• Check the panel’s model code and the installer on MCS’s own register. No MCS certificate means no SEG export income.
• Ask for the datasheet and read three lines: product warranty years, power warranty years and annual degradation.
• Refuse Hi-MO 5 PERC stock at n-type prices. Clearance pricing or nothing.
• Check the panel size against your roof layout, because the X10 is longer than the Hi-MO 6.
• Ask whether the installer’s workmanship warranty is insurance-backed and how long it runs.
• Compare pence per watt across quotes, not total price, since array sizes and roof fittings differ.
• Check the installer’s reviews and trading history before the brand’s. Our guide to choosing a solar installer shows how.

Longi vs Jinko, JA Solar, Trina and AIKO

Efficiency and warranty vary by batch and distributor. Rival figures follow our own reviews, linked below.

For the head-to-head detail, read AIKO vs Longi vs JA Solar, AIKO vs Jinko, Jinko vs JA Solar vs Trina and the Jinko and AIKO reviews. Across all of them, the model generation and the installer decide outcomes more often than brand loyalty does.

Where Longi wins

• Back-contact panels with no front gridlines, in a size built for houses.
• The X10’s 30-year power warranty and 0.35% annual degradation.
• Scale: a manufacturer shipping 80 to 90 GW a year isn’t likely to vanish.

Where it doesn’t

• A premium of about £50 to £150 per ten panels over JA Solar.
• Old Hi-MO 5 stock still circulates, and some quotes don’t say which model you’re getting.
• A 15-year product warranty on most trims, against 25 years on some rivals’ current stock.
• Two loss-making years for the manufacturer, which is why the installer’s cover matters.

The verdict in four scores

Longi earned its place on UK quotes with scale and a range that now includes some of the best rooftop panels on sale. Buy the X10 or Hi-MO 6 at a fair price per watt, keep the datasheet with your MCS certificate, and check the installer as carefully as the panel. If you’re still shortlisting brands, our roundup of the best solar panels for UK homes in 2026 puts Longi in context.

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