HPBC cell efficiency >25%

Hybrid Passivated Back Contact cells achieve cell-level efficiency exceeding 25% — among the highest mass-produced silicon cell efficiencies available. Module-level efficiency lands at 22% after frame, gaps, glass, and encapsulation losses. The gap from 25% cell to 22% module is normal across all manufacturers; what matters is LONGi's cell efficiency starts higher than conventional designs.

No front busbars · cleaner aesthetic

Conventional silicon panels have visible horizontal silver busbars across each cell. HPBC moves all electrical contacts to the rear, leaving the front face as a clean uniform deep-black surface. The aesthetic difference is substantial — particularly relevant for visible residential arrays where appearance matters alongside output. Also a small efficiency win (no busbar shading on front face).

Power output at year 25

87.4% of nominal power guaranteed at year 25 under LONGi's standard product warranty — a linear ~0.5% per year degradation curve. Conventional panels typically guarantee 80–85% at year 25 with a steeper degradation curve. LONGi's field-deployed fleet from 2015 onwards is hitting the warranty curve comfortably; in many cases panels are tracking 92%+ at year 10.

Low-light performance

HPBC cells perform meaningfully better than conventional designs in low-light conditions — overcast UK weather, early morning, late afternoon, and winter shoulder seasons. Real-world UK annual yield typically tracks 7–12% above conventional panels of equivalent nameplate wattage. The gap is largest in cloudier regions (Manchester, Scotland) and smallest in sunnier regions (south coast).

Temperature coefficient

Temperature coefficient around −0.29% per °C — meaningfully better than conventional crystalline silicon (~−0.35% per °C). On hot summer days when conventional panels lose 10–15% performance vs lab conditions, the HPBC HJ-MO 6 loses 8–12%. The gap matters most in commercial barn roofs and south-facing residential roofs where back-of-panel temperatures can reach 70°C+ at peak.

Micro-crack resistance

Full back-side welding plus the HPBC cell architecture together resist micro-cracking better than conventional front-busbar designs. Micro-cracks accumulate over the panel's life through thermal cycling, hail impact, snow load, and installer foot traffic during commissioning. Better micro-crack resistance translates to slower power degradation in practice — particularly relevant for panels in exposed locations.

Snow and hail tolerance

IEC 61215 hail test passed at the 25 mm ball impact standard. Snow load rating typically 5,400 Pa front, 2,400 Pa rear — comfortably covers any UK roof snow load. The HPBC back-contact design is structurally similar to conventional crystalline panels in mechanical terms; the differences are at the cell-electronics level, not the structural level.

Field-proven since 2015

LONGi has been shipping HPBC-architecture panels since 2015 (the original HI-MO series), with a decade of field-deployed performance data behind the HI-MO 6 Explorer's design. Cumulative LONGi panel installs exceed 200 GW globally — the largest fleet of any single PV manufacturer. The accumulated field data is what underpins the 25-year warranty's bankability.

PID resistance

Potential Induced Degradation (PID) — gradual power loss caused by stray voltage between the panel and grounded frame — is a real issue for panels in humid climates or sub-optimal earthing. HI-MO 6 Explorer is PID-resistant to IEC 62804 testing. Particularly relevant for older UK buildings with marginal earthing and coastal properties with salt-air humidity.

1 · HPBC silicon cell

Mono-crystalline silicon wafer with Hybrid Passivated Back Contact cell architecture. All electrical contacts on the rear face, leaving the front face busbar-free. Cell efficiency exceeds 25% — among the highest mass-produced silicon cells available. LONGi manufactures the silicon ingots, wafers, and cells in-house, giving vertical integration that other PV brands lack.

2 · Anti-reflective front glass

3.2 mm tempered low-iron solar glass with anti-reflective coating (ARC). The ARC reduces front-surface reflection from ~8% (uncoated glass) to ~2%, adding ~5% to delivered power across the panel's life. Low-iron glass transmits more of the solar spectrum than standard window glass. Tempered for hail and snow load resistance.

3 · EVA / POE encapsulation

Encapsulation films between the cells and the front glass / rear backsheet. EVA (Ethylene Vinyl Acetate) for standard variants, POE (Polyolefin Elastomer) for premium variants with bifacial dual-glass construction. The encapsulation must remain optically clear and electrically isolating for 25+ years through UV exposure and thermal cycling — LONGi has been refining this through 200+ GW of field-deployed panels since 2015.

4 · Backsheet or glass back

Standard variants use a multi-layer polymer backsheet (white or black depending on aesthetic configuration). Dual-glass bifacial variants use a tempered glass rear face instead of polymer backsheet — heavier and more expensive, but used in commercial barn-roof applications where the underside-light reflection from the ground or roof surface adds 5–10% to yield.

5 · Anodised aluminium frame

30 mm or 35 mm anodised aluminium frame, structurally bonded to the glass-cell-backsheet stack. Black anodised for the all-black aesthetic variant, natural silver for the standard variant. Frame doubles as the structural mount-point and the earth-bonding path. 25-year warranty includes frame corrosion resistance.

ORDER CONFIGURATION
Aesthetic: All-Black or Standard Frame

All-Black — black anodised frame + black backsheet + busbar-free HPBC front = uniform deep-black appearance. The right pick for visible residential roofs where aesthetics matter, particularly for new builds and signature renovations where the array is a designed-in architectural feature.

Standard Frame — silver anodised frame + white backsheet + busbar-free HPBC front. Around 5–8% cheaper per panel than All-Black due to standard frame and backsheet pricing. The right pick for commercial barn roofs, ground-mount arrays, large rear-roof installs not visible from the street, and budget-driven £/watt briefs where every panel cost is multiplied across many panels. Same electrical performance either configuration.

25-year product + performance warranty

LONGi warrants the HI-MO 6 Explorer for 25 years on both product (defects) and performance (87.4% of nominal at year 25). Two separate guarantees — a defect that emerges after year 12 is still covered. Among the longest combined warranties in mainstream PV. LONGi's 200+ GW deployed fleet and Tier 1 financial stability make the 25-year claim genuinely credible — not a smaller-brand warranty backed by a company that might not exist in 20 years.

Tier 1 bankability

Bloomberg New Energy Finance rates LONGi as a Tier 1 manufacturer — the highest tier for PV bankability, meaning major project financiers approve LONGi panels for non-recourse project finance. For commercial solar customers this matters operationally: the bank's solar project financing is essentially impossible to secure on lower-tier panels. For residential customers it's a proxy signal that the manufacturer will still exist in 2050 to honour the warranty.

UK distributor support

LONGi has established UK distribution and technical support — Segen and Midsummer Energy among others. Spare panels (matched to the original install for visual consistency) and warranty claim handling go through the distributor. Lead time for replacement panels typically 2–4 weeks. Critical for commercial sites where a faulty panel needs to be swapped out without an extended outage to the affected string.

Linear performance guarantee

LONGi's performance warranty is "linear" — guaranteed power decreases gradually from 98% at year 1 to 87.4% at year 25, a straight-line curve. Compared with "step" warranties (e.g. "90% at year 10, 80% at year 25") the linear version is more generous in the middle years and easier to claim against. If your panel hits the curve in year 15, you have a valid claim even if it's still above 87.4%.

SYSTEM PROTECTOR
Annual monitoring vigilance

A panel that's quietly degrading faster than expected won't show up unless someone's looking. CleverBloom's solar service plan includes annual remote monitoring review — comparing actual yield against predicted yield for the property's location and aspect. Catches anomalies (one string under-producing, micro-cracking damage from a recent storm, panel soiling) early enough that warranty claims fall within the manufacturer's claim window.

SYSTEM PROTECTOR
Panel cleaning · selective

UK residential arrays generally don't need cleaning — rainfall washes them adequately for the residential yield case. Commercial arrays on shallow-pitch roofs in dusty environments (workshops, agricultural buildings) sometimes benefit from periodic cleaning. The HPBC anti-dust coating helps but doesn't eliminate the need entirely. CleverBloom's commercial service plan includes annual cleaning where the site profile warrants it.