Longi Solar panels are the most-installed brand in the UK by volume as of 2026 (MCS data)
If you are researching solar panels in 2026, you will almost certainly encounter Longi. The question is whether market dominance by volume translates to a good choice for your home. MCS installation statistics show Longi panels lead in total UK rooftop deployments for 2025 and 2026 (DESNZ MCS Installations Dashboard, 2026).
Longi panels cost £5,500 to £7,500 for a typical 4kW system in 2026. This is competitive with other tier-1 brands. The Hi-MO 6 series offers above-average efficiency for limited roof space.
- Longi is the most-installed solar panel brand in the UK by volume in 2026.
- Hi-MO 6 series achieves 22.5-23.0% efficiency, above the 21.5% industry average.
- Hi-MO 5 series efficiency (21.2-21.8%) is slightly below the 2026 average.
- Both series come with a 25-year product and 25-year linear output warranty.
- Longi holds BloombergNEF tier-1 bankability status for low-risk project financing.
- Longi Solar panels are the most-installed brand in the UK by volume as of 2026 (MCS data)
- Longi panel efficiency ranges from 21.2% to 23.0% depending on the series
- Longi offers a 25-year product warranty and a 25-year linear power output warranty
- Quick numbers Longi Hi-MO 6 vs UK average panel (table format)
- Longi panels are MCS-certified and eligible for UK Smart Export Guarantee payments
- Longi panels cost 5–10% less per watt than premium European brands in 2026
- The direct answer Longi panels offer good value for UK homes with standard roofs
- How to verify a Longi installer MCS certification and TrustMark registration
Longi is a Chinese manufacturer with tier-1 bankability status from BloombergNEF, meaning financial institutions consider it low-risk for project financing (BloombergNEF Tier-1 Solar Manufacturer List, 2026). This status is important because it indicates the company is likely to honour its 25-year warranties. This review compares Longi against market-average panels on efficiency, warranty, and real-world degradation, using published data rather than anecdotal experience.
Longi panel efficiency ranges from 21.2% to 23.0% depending on the series
Longi offers two main series for UK residential use: the Hi-MO 5 and the Hi-MO 6. The Hi-MO 5 series uses PERC (Passivated Emitter and Rear Cell) technology and achieves efficiency ratings of 21.2% to 21.8%. The Hi-MO 6 series uses HPBC (Hybrid Passivated Back Contact) technology and achieves 22.5% to 23.0% efficiency (Longi Hi-MO 5 and Hi-MO 6 datasheets, 2026).
The industry average efficiency for 2026 residential panels is 21.5% (Energy Saving Trust, 2026). This means the Hi-MO 5 is slightly below average, while the Hi-MO 6 is above average. The efficiency difference matters most when you have limited roof space. For a typical UK 3-bed semi with a 4kW system (10–12 panels), the difference between 21.5% and 23.0% efficiency means roughly one fewer panel needed for the same output.
Longi offers a 25-year product warranty and a 25-year linear power output warranty
Longi provides a 25-year product warranty covering manufacturing defects and a 25-year linear power output warranty. The output warranty for the Hi-MO 6 guarantees 84.8% of nominal power after 25 years, with year 1 at 98% and a linear degradation rate of 0.55% per year thereafter (Longi warranty documentation, 2026).
This matches the industry standard for tier-1 panels, which is a 25-year product warranty and a 25-year linear output warranty (MCS standard for solar panel warranties, 2026). The degradation rate is competitive: a 0.55% annual decline means after 10 years the panel still produces 93.5% of its rated power, compared to some budget panels that degrade at 0.7% per year.
Quick numbers Longi Hi-MO 6 vs UK average panel (table format)
| Specification | Longi Hi-MO 6 (400W) | Longi Hi-MO 5 (390W) | UK average tier-1 panel (400W) |
|---|---|---|---|
| Efficiency (%) | 22.5–23.0 | 21.2–21.8 | 21.5 |
| Power output (W) | 400 | 390 | 400 |
| Warranty product (years) | 25 | 25 | 25 |
| Warranty output (years) | 25 | 25 | 25 |
| Degradation after 25 years (%) | 84.8 | 84.8 | 85.0 (typical) |
| Typical price per panel (£, 2026) | £110–£130 | £95–£115 | £120–£150 |
Data sources: Longi datasheets (Longi, 2026), Energy Saving Trust panel comparison (Energy Saving Trust, 2026), Solar Energy UK market report (Solar Energy UK, 2026).
Longi panels are MCS-certified and eligible for UK Smart Export Guarantee payments
All Longi panels sold in the UK are MCS-certified, with certificate numbers available on the MCS register (MCS product register, 2026). MCS certification is a prerequisite for eligibility under the Smart Export Guarantee (SEG), which pays you for electricity you export to the grid.
To receive SEG payments, you need both MCS-certified panels and an MCS-certified installer. Longi panels meet the panel requirement. Typical SEG rates in 2026 range from 5p to 15p per kWh exported, depending on your energy supplier (Ofgem SEG published rates, 2026). For a 4kW system exporting roughly half its generation, this could add £80–£240 per year in income (GOV.UK SEG guidance, 2026).
Longi panels cost 5–10% less per watt than premium European brands in 2026
The average installed cost per watt for a Longi system in 2026 is £1.50–£2.00, based on installer quotes and Solar Energy UK data (Solar Energy UK installer survey, 2026). Premium European brands such as SunPower and REC typically cost £1.80–£2.50 per watt installed.
This 5–10% upfront saving on the hardware cost does not come with a significant performance penalty for most UK homes. Based on DESNZ solar PV cost data, the typical payback period for a Longi system is 10–14 years, compared to 12–16 years for premium brands (DESNZ solar PV cost data, 2026). The difference is driven by the lower initial investment rather than higher output.
The direct answer Longi panels offer good value for UK homes with standard roofs
Longi panels are a reliable tier-1 option for homeowners prioritising upfront cost and solid warranties. They are not the most efficient panels available, but their efficiency is sufficient for most UK roof sizes where 10–16 panels are typical (Energy Saving Trust solar panel suitability guidance, 2026).
They are best suited for south-facing or east-west roofs where space is not extremely limited. If you have a small, north-facing roof or unusual constraints, higher-efficiency panels from SunPower or REC may justify their premium. However, for the majority of UK homes, Longi delivers the best balance of cost, warranty, and performance. MCS installation data confirms that UK homeowners are choosing Longi in large numbers for exactly this reason (MCS installation data, 2026).
How to compare solar panel efficiency ratings
How to verify a Longi installer MCS certification and TrustMark registration
Before committing to an installation, verify that your installer holds MCS certification for solar PV. You can check this free of charge on the MCS register (MCS installer register, 2026). Additionally, TrustMark registration ensures consumer protection and government-endorsed quality standards (TrustMark, 2026).
Ask your installer for the Longi panel serial numbers and confirm that warranty registration is completed after installation. Without this step, you may lose the 25-year product warranty. The GOV.UK consumer advice page recommends checking both MCS and TrustMark before paying any deposit (GOV.UK consumer advice, 2026).
Solar panel installation checklist for UK homeowners
Frequently Asked Questions
Yes, Longi panels are a reliable choice. They hold BloombergNEF tier-1 bankability status and offer a 25-year product warranty. The Hi-MO 6 series efficiency of up to 23.0% is above the 2026 industry average of 21.5% (Energy Saving Trust, 2026).
Longi panel efficiency ranges from 21.2% to 23.0% depending on the series. The Hi-MO 5 achieves 21.2-21.8% and the Hi-MO 6 achieves 22.5-23.0% (Longi datasheets, 2026). The 2026 industry average is 21.5% (Energy Saving Trust, 2026).
Longi offers a 25-year product warranty covering manufacturing defects and a 25-year linear power output warranty. This matches the standard warranty period for most tier-1 solar panels (MCS, 2026).
Longi panels are manufactured in China. The company is headquartered in Xi'an and is the world's largest monocrystalline silicon wafer manufacturer (BloombergNEF Tier-1 Solar Manufacturer List, 2026).
Longi panels are designed to last over 25 years. They come with a 25-year product warranty and a 25-year linear power output warranty, guaranteeing at least 80% of original output after 25 years (Longi warranty documentation, 2026).
