LONGi Solar Panels Review (2026): The Best Back-Contact Panel for the Money?
LONGi is the biggest solar manufacturer on the planet — and its Hi-MO X10 is the back-contact panel that takes on Aiko for less. Here’s our honest verdict on efficiency, shade performance, the warranty small print and who it’s right for.
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Who are LONGi?
LONGi Green Energy Technology was founded in 2000 and is headquartered in Xi’an, China. It started as a silicon wafer maker and essentially won the argument that monocrystalline would beat polycrystalline — which is why virtually every panel sold today is mono (see mono vs poly). It is now the largest solar manufacturer in the world by volume, with over 100GW of annual capacity, listed on the Shanghai Stock Exchange, and holds a string of world records for cell efficiency (see LONGi’s global site). Panels are made mainly in China, with factories in Malaysia and Vietnam too.
That scale is the point for a homeowner. A company shipping this many panels has the balance sheet to honour a 30-year warranty and the R&D budget to keep its cell technology at the front of the pack — which is exactly what the Hi-MO X10 shows. For how LONGi sits against the whole market, see our best solar panels UK guide.
Hi-MO X10 vs Hi-MO 6
| Hi-MO X10 (premium) | Hi-MO 6 (mainstream) | |
|---|---|---|
| Cell technology | HPBC 2.0 back-contact, n-type | TOPCon / HPBC 1.0, n-type |
| Residential power | ~470–490W | ~430–450W |
| Efficiency | Up to ~24% | ~22–23% |
| Shade tolerance | Excellent (~70% less loss) | Standard |
| Looks | Unbroken all-black front | All-black, visible busbars |
| Performance warranty | 30 years, 88.85% at yr 30 | 25–30 years |
| Price bracket | Affordable premium | Mainstream (≈ JA / Jinko) |
Most UK homeowners looking at LONGi in 2026 are looking at the Hi-MO X10, and that’s what this review focuses on. The Hi-MO 6 is a perfectly good mainstream panel, but if you’re going to buy it you may as well compare it directly with JA Solar and Perlight, because it competes on price rather than technology.
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Get My LONGi Price →Our scores
Our rating
LONGi Hi-MO X10
★★★★½ Back-contact performance, sensible price
The bottom line: Aiko-level performance from the world’s biggest manufacturer, for less. Only the 15-year standard product warranty stops it scoring higher — ask for the 25-year version.
Get my LONGi price →Why back-contact matters
On a conventional panel, thin silver lines (busbars) run across the front of every cell to collect the current. They shade a small part of each cell and they’re why you can see a grid on the panel. Back-contact cells move all of that wiring to the rear. The front is unbroken, so more of the surface generates power (higher efficiency), the panel is a clean all-black slab (better looks), and — the bit that matters most in the UK — partial shade hurts far less.
LONGi quotes roughly 70% less shading loss than a standard TOPCon panel: with part of the array shaded, an X10 holds around 92% of its output where a conventional panel drops to about 65%. On a UK roof with a chimney, a dormer, a neighbour’s tree or a satellite dish, that’s not a spec-sheet nicety — it’s the difference between an array that underperforms every afternoon and one that doesn’t. If shading is your issue, also see optimisers and micro-inverters, because back-contact panels reduce the need for them.
Efficiency & real-world output
The Hi-MO X10 reaches up to 24% efficiency in its residential format — right at the top of the market alongside Aiko, and a clear step above the 22–23% of mainstream panels like JA Solar or Perlight. On a small roof that translates directly into more kW for the same space.
Two numbers back up the headline. The temperature coefficient is -0.26%/°C, so it holds output well on hot days; and degradation is under 1% in year one, then 0.35% a year, which is why LONGi can guarantee 88.85% output at year 30. That’s a slower fade than most TOPCon panels (typically 0.4–0.5%/yr), though not quite REC’s 0.25%. For what these figures mean for your bills see our solar panel efficiency guide.
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Get My LONGi Price →The warranty — read the small print
| Cover | Hi-MO X10 |
|---|---|
| Product warranty (faults/defects) | 15 years standard — up to 25 years on some UK stock |
| Performance warranty | 30 years, linear |
| Output guaranteed at year 30 | 88.85% |
| Year-one degradation | ≤ 1% |
| Annual degradation thereafter | 0.35% |
Here’s the honest wrinkle. The 30-year performance warranty is excellent. But the product warranty — the one that covers the panel actually failing — is 15 years on the standard datasheet. That’s fine, but it’s shorter than the 25 years JA Solar offers on the DeepBlue 4.0 Pro or the 30 years Perlight markets in the UK. Some UK distributors and installers supply X10 stock with an extended 25-year product warranty, so it’s worth asking specifically which version you’re being quoted and getting it in writing. As always, the installer’s own workmanship guarantee sits alongside — see how to choose a solar installer.
UK price
This is where the X10 makes its case. It’s a premium back-contact panel at an affordable-premium price: roughly £160–£300 per panel installed, and a typical 4–5kW system around £6,000–£8,500 fitted with 0% VAT. That’s usually £20–£50 a panel less than Aiko for comparable technology, and £100+ a panel below SunPower Maxeon. The mainstream Hi-MO 6 prices alongside JA Solar and Jinko, so a 4–5kW system there is nearer £5,000–£7,000.
Judged on cost per kWh over 25–30 years, the X10 is one of the strongest premium buys available — you’re getting top-tier efficiency and shade tolerance without paying the full premium-brand tax. For the full breakdown see our cost of solar panels guide and the grants available in 2026.
LONGi vs Aiko, JA Solar & REC
| Brand | Best for | Efficiency | Product warranty | Price |
|---|---|---|---|---|
| LONGi Hi-MO X10 | Back-contact performance at a fair price | Up to ~24% | 15 yrs (25 on some stock) | Affordable premium |
| Aiko | Absolute peak efficiency, small roofs | Up to ~24.5% | 15–25 yrs | Premium |
| REC Alpha Pure-RX | Longevity, 92% at 25 yrs | Up to 22.6% | 20–25 yrs | Premium |
| JA Solar | Best mainstream value | ~22.7% | 25 yrs | Mid |
The honest summary. Aiko and LONGi are the genuine head-to-head — both back-contact, both all-black, both superb in shade. Aiko edges the efficiency number; LONGi is cheaper and comes from a company several times Aiko’s size. Between them it often comes down to which your installer stocks and prices better. REC is the choice if longevity and the labour-inclusive warranty matter more than peak efficiency. JA Solar is what you buy when you’ve got a big, unshaded roof and just want the best £-per-watt.
Pros & cons
Pros
- Back-contact cells: up to 24% efficiency and ~70% less shading loss
- Usually £20–£50 a panel cheaper than Aiko for similar tech
- 30-year performance warranty, 88.85% at year 30
- World’s largest manufacturer — bankable for the long term
- Clean, unbroken all-black finish
- Widely stocked by UK distributors
Cons
- Standard product warranty only 15 years — ask for the 25-year version
- Made in China (if that matters to you)
- Aiko still edges it on headline efficiency
- Hi-MO 6 mainstream range is unremarkable vs JA / Jinko
Our verdict
4.5 / 5 — the smartest way to buy back-contact performance. The Hi-MO X10 gives you what makes Aiko special — top-tier efficiency, an unbroken black face and outstanding shade tolerance — from the biggest, most bankable manufacturer in the world, and usually for less money. If your roof is small, awkward or partly shaded, it should be on your shortlist above almost anything else.
The one thing to do before you sign: ask which product warranty you’re getting. The 15-year standard is acceptable; the 25-year extended version some UK installers supply makes this a near-perfect package. Get that in writing and the X10 is very hard to beat.
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LONGi solar panels: frequently asked questions
Are LONGi solar panels any good?
Yes — LONGi is the world’s largest solar manufacturer and a Tier 1 brand, and its Hi-MO X10 is one of the best residential panels you can buy: back-contact cells at up to 24% efficiency, excellent shade tolerance, and a 30-year performance warranty. The mainstream Hi-MO 6 range is a solid value option. The only real caveats are that the standard product warranty is 15 years unless your installer offers the extended 25-year version, and the panels are made in China.
Where are LONGi solar panels made and who owns LONGi?
LONGi Green Energy Technology was founded in 2000 and is headquartered in Xi’an, China, where most of its panels are made, with additional factories in Malaysia and Vietnam. It is a publicly listed company on the Shanghai Stock Exchange and the largest solar manufacturer in the world by volume, with over 100GW of annual capacity.
What is the LONGi Hi-MO X10?
The Hi-MO X10 is LONGi’s flagship residential panel, using HPBC 2.0 back-contact cells — all the wiring is on the rear, so the front is unbroken black and more of the surface generates power. Residential versions deliver around 470–490W at up to 24% efficiency, with a temperature coefficient of -0.26%/°C and around 70% less output loss under partial shade than a conventional TOPCon panel.
What warranty do LONGi solar panels have?
The Hi-MO X10 carries a 30-year linear performance warranty guaranteeing 88.85% of original output at year 30, with degradation of under 1% in year one and 0.35% a year after that. The product warranty is 15 years as standard, with some UK installers offering an extended 25-year product warranty — worth asking for on your quote.
How much do LONGi solar panels cost in the UK?
The Hi-MO X10 sits at the affordable end of premium: roughly £160–£300 per panel installed, with a typical 4–5kW system landing around £6,000–£8,500 fitted with 0% VAT until 31 March 2027. That’s usually £20–£50 a panel less than Aiko and well below SunPower Maxeon, while the mainstream Hi-MO 6 is priced with JA Solar and Jinko.
LONGi vs Aiko vs JA Solar — which is best?
LONGi Hi-MO X10 and Aiko are the two back-contact rivals: Aiko edges the efficiency headline, LONGi is a little cheaper and comes from a far larger company. Both are excellent for small or partly-shaded roofs. JA Solar is the mainstream value pick with conventional TOPCon cells. If you want back-contact performance, LONGi is arguably the smarter buy; if you just want the best £-per-watt on a big open roof, JA Solar.
Figures are typical 2026 UK estimates for guidance only; wattages, efficiency, warranty terms and prices vary by exact model, distributor and installer — confirm the specific product warranty on your quote. Always use an MCS-certified installer. 0% VAT on solar applies until 31 March 2027 per HMRC. Sources: LONGi specifications and UK installer pricing.