LONGi Solar Panels Review UK: Hi-MO Range, Warranty & Pricing

LONGi is the largest monocrystalline silicon wafer and module manufacturer in the world, and its panels are quoted by UK installers constantly — often without homeowners recognising the name. Founded in Xi'an, China in 2000 as Xi'an LONGi Silicon Materials Corp and renamed LONGi Green Energy Technology in 2017, the company is listed on the Shanghai Stock Exchange (601012) and shipped 86.58 GW of modules in 2025 alone, according to its own 2025 annual report. This review covers what LONGi actually sells to UK homes, real warranty terms per range, UK hardware pricing, and how it stacks up against the other manufacturers we've reviewed.

Is LONGi a Tier 1 manufacturer?

Yes. LONGi has appeared on BloombergNEF's Tier 1 PV module list every quarter through Q1 2026, including a "double Tier 1" classification for both modules and storage that quarter, according to LONGi's own press coverage of the BNEF list. BNEF tightened its Tier 1 criteria through 2024–2025, shrinking the list from roughly 40 manufacturers to around 20 — LONGi has stayed on it throughout. It was also named a "Top Performer" in the Kiwa PVEL 2025 PV Module Reliability Scorecard for the eighth time, scoring strongly across thermal cycling, mechanical stress, PID and LID/LETID testing. Our Tier 1 vs Tier 2 guide explains what that label does and doesn't tell you — it measures financial bankability, not panel quality directly, though the two tend to correlate.

LONGi also holds several independently certified world records: 25.4% module efficiency (HPBC 2.0 technology), certified by Fraunhofer ISE in April 2025, and a 27.81% back-contact cell efficiency certified by ISFH. These are lab records rather than figures on panels you'll actually buy, but they signal where the company's R&D is heading.

LONGi's UK-sold panel ranges

LONGi's catalogue is large, but three ranges show up on UK residential quotes and retailer listings:

Hi-MO X10 — flagship back-contact

The Hi-MO X10 is LONGi's current flagship, using HPBC 2.0 (Hybrid Passivated Back Contact) N-type cells with no visible front busbars. UK-sold panels in this range run 480–540W depending on the specific SKU, with a 30-year performance warranty (99% output in year one, degrading at ≤0.35% a year, ≥88.85% remaining at year 30) per LONGi's own datasheet. We've covered this panel head-to-head against Aiko's rival back-contact module in our Aiko vs LONGi comparison — worth reading if you're choosing between the two flagship back-contact panels rather than deciding whether LONGi as a brand suits you.

Hi-MO 6 — mainstream HPBC

The Hi-MO 6 range (sold under Explorer, Scientist, Guardian and Artist sub-variants) spans 410–585W and is company-wide HPBC technology per LONGi's own product pages. It's the range most commonly stocked by UK trade suppliers — Midsummer Wholesale, Plug In Solar and Solar Trading UK all list Hi-MO 6 SKUs. Warranty terms vary by exact model (12 or 15-year product warranty, 25 or 30-year performance warranty depending on SKU), so always check the datasheet for the specific model on your quote rather than assuming a blanket figure across the range.

Hi-MO 5 — older P-type generation

The Hi-MO 5 (475–585W) is LONGi's older mono-PERC generation using gallium-doped P-type wafers rather than the N-type cells in the X10 and 6 ranges, rated at 21.2–21.8% efficiency — a step below the Hi-MO 6's high-efficiency N-type cells. It carries a 12-year product warranty. It's still sold in the UK (Plug In Solar lists a 550W Hi-MO 5 model) and turns up on budget-focused quotes, but if efficiency and long-term degradation matter more than upfront price, the Hi-MO 6 or X10 are the better-specified choice.

UK pricing

LONGi doesn't sell direct to UK homeowners — its main UK trade channels, Segen and Midsummer Wholesale, are B2B and require an installer login to see pricing. Smaller UK retailers that publish prices openly give a workable sense of hardware cost (excluding installation):

• Hi-MO X10 480W (black frame): around £72 excluding VAT, per ITS Technologies' listed UK pricing.
• Hi-MO X10 530W (dual glass): around £76 excluding VAT, per the same UK retailer.
• Hi-MO 6 425W (all-black): around £94 including VAT per panel, per The Eco Supermarket's UK listing.

These are independent UK retailer prices, not LONGi's own pricing, and they cover hardware only — mounting, cabling and installation labour are quoted separately by your installer. Treat them as a rough per-panel benchmark, not a fixed cost; a full system quote from an MCS-certified installer is the only reliable number for your roof.

MCS certification

LONGi panels are commonly listed on the MCS product certification database under model-specific certificate numbers — UK retailers selling the Hi-MO 6 425W and Hi-MO X10 480W models both cite matching MCS certificate references (e.g. BABT8771-series numbers) independently of each other, which is a reasonable secondary signal of certification. Certification is tracked per model rather than per brand, though, so before signing a quote, ask your installer to confirm the exact LONGi model you're being fitted with is currently on the MCS product database — this is what keeps you eligible for the Smart Export Guarantee. See our MCS certificate guide for what the certificate actually covers.

Supply chain due diligence

Worth a balanced mention: LONGi has had US Customs and Border Protection detain shipments under forced-labour import controls in the past (roughly 40 MW detained in late 2021 under the precursor to the UFLPA, most of which CBP later released after LONGi provided traceability evidence), and its Vietnamese subsidiary was found by US Commerce in 2023 to have circumvented American anti-dumping duties using Chinese-origin wafers. Both of these are US customs and trade-remedy matters, not UK or EU import restrictions — there is no confirmed UK ban or restriction on LONGi panels, and the company remains one of the most widely fitted brands by UK MCS-certified installers. It's context for due diligence if that matters to you, not a reason to rule the brand out for a UK installation.

How LONGi compares

Our solar panel manufacturers guide covers the wider market, but in short: LONGi's Hi-MO X10 sits in the same premium back-contact bracket as Aiko's Neostar 3S+, with near-identical 30-year performance warranties, though LONGi's product warranty (15 years on its own datasheet, sometimes listed as 25 by UK retailers — check the specific SKU) trails Aiko's confirmed 25-year cover and JA Solar's 25-year product warranty on its DeepBlue range. Where LONGi wins is scale and bankability: it's shipped more modules globally than almost anyone, which matters for warranty claims still being honoured a decade from now. For a mainstream, well-unshaded roof, the Hi-MO 6 is the practical middle ground between LONGi's flagship X10 and cheaper P-type alternatives from other brands.

Our verdict

LONGi is a legitimate, heavily bankable Tier 1 manufacturer rather than an obscure import, and its panels are fitted routinely by UK MCS-certified installers across budget, mainstream and premium tiers. Choose the Hi-MO X10 if you want flagship back-contact efficiency and are comparing it directly against Aiko; choose the Hi-MO 6 for a well-specified mainstream install; and treat the older Hi-MO 5 as a budget option only if the quoted price genuinely beats the efficiency gap. Whichever range you're quoted, confirm the exact model is currently MCS-listed and get it fitted by an MCS-certified installer to keep your Smart Export Guarantee eligibility intact.