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Longi Solar Brand review

LGi7-72HTD-620M

620 Wp Monocrystalline
ComparePV verdict

Strong in heat, short guarantee

Rank 1,436 of 14,129
Compare panels Datasheet PDF
Power (Wp)
620
Typical for its class
Efficiency (%)
23.10
Strong · top 15%
Density (Wp/m²)
231.3
Strong · top 15%
Temp (%/°C)
-0.280
Strong · top 14%
Weight (kg)
31.0
Strong · 1.0 kg below median
Warranty (yrs)
25
Weak · bottom 10%

The LONGi ROOF 4 series introduces a new level of quality to home energy systems, basing its operation on advanced HPBC cell technology. The key innovation is the complete removal of busbars from the front of the module, which allows for significantly more efficient light absorption and eliminates losses resulting from cell shading by metal elements. This approach ensures that these panels offer higher energy conversion efficiency even with limited mounting space, solving the problem of small or complex roof areas. The aesthetic, deep black design makes the installation an integral part of the building rather than just a technical device. Modules in this series are characterized by exceptional thermal stability, which guarantees high power production on hot days when traditional panels lose efficiency. Additionally, the reinforced cell structure provides increased resistance to micro-cracks and weather conditions, directly translating into the security of a long-term investment. The ROOF 4 series is a choice for homeowners and businesses who do not want to compromise between performance and appearance. Thanks to optimized performance in low light, these systems generate more energy in the morning and evening, outperforming the competition in terms of annual kilowatt-hour yield per kilowatt of installed capacity.

Ranking

6,116 panels in the 520-720 W band, all technologies
Metric This panel Median Position in segment Overall rank
Module efficiency 23.10% 22.30% Strong · top 15% 1,617
Power density 231.3 222.8 Strong · top 15% 1,665
Temperature coefficient -0.280 -0.300 Strong · top 14% 1,347
Weight per kWp 50.0 53.1 Strong · top 23% 3,329
Performance warranty 25 yrs 30 yrs Weak · bottom 10% 9,912
Colour key Strong - top 25% Typical - middle 50% Weak - bottom 25%

Signals from the data

7 positive · 3 caution
Best for

Residential, commercial and hot-climate.

Not ideal for

Owners who want a long output guarantee.

Strengths
-0.280 %/°C temperature coefficient

Top 14% of the 520-720 W band, against a median of -0.300.

23.10% module efficiency

Top 15% of the 520-720 W band, against a median of 22.30%.

231.3 watts per square metre

Top 15% of the 520-720 W band, against a median of 222.8.

Watch-outs
25 year performance warranty

Bottom 10% of the 520-720 W band, against a median of 30 yrs.

What owners get
Zero front busbars, up to 23.1% efficiency

HPBC technology removes metallic busbars from the cell front, allowing the ROOF 4 series to reach 22.4-23.1% efficiency - matching or exceeding N-type TOPCon peer comparables (HT-SAAE 23%, MY Solar 22.95%, Weran Solar 23%), despite those competitors being bifacial.

Certified hot-spot resistance

LONGi's HPBC 2.0 cell architecture is TÜV Rheinland certified for anti-shading performance, with hot-spot temperatures up to 77°C lower than TOPCon modules. Current is routed around only the shaded cell rather than an entire bypass-diode string, reducing losses from partial shading by chimneys or antennas.

Improved power temperature coefficient

The HPBC design delivers a power temperature coefficient of approximately -0.26%/°C, about 0.03 percentage points better than typical TOPCon modules. In practice this means a smaller output drop on hot summer days compared to older PERC technology.

Symmetrical 25-year Tier-1 warranty

Both product and power warranties are set equally at 25 years, meeting premium-segment standards, and manufacturer LONGi (founded 2000, Tier-1 bankable status) is the world's largest module producer, limiting risk of unfulfilled warranty claims down the line.

Trade-offs
No bifacial variant available

The ROOF 4 series is monofacial only, while a direct peer comparable of identical power class (MY Solar G&A N-Type TOPCon Bifacial, 620 Wp, 22.95%) offers additional rear-side yield. For ground-mount or high-albedo installations this represents a real energy-yield gap versus that competitor.

Shorter warranty than LONGi's own flagship lines

While ROOF 4 carries a 25-year power warranty, LONGi's newer flagship back-contact lines (Hi-MO X9/X10), built on related HPBC technology, extend coverage to 30 years. Buyers seeking the longest protection period within LONGi's portfolio should consider those series instead of ROOF 4.

Notes from the database
  • Efficiency of 23.1% is 1.3pp above the database median (21.8%)
  • 231.3 W/m² power density - 13.2 W/m² more than database median (218.1 W/m²), more power per roof area
  • Temperature coefficient of -0.28%/°C matches the database median
  • At 31.0 kg, this panel is 4.5 kg heavier than the database median (26.5 kg) - more demanding for installation crews
  • Ranked #1617 out of 14129 panels for efficiency in the database

Specifications

Open datasheet PDF
Nominal power (Pmax) 620 Wp Nameplate at 1000 W/m², 25 °C
Module efficiency 23.10 % Strong Segment median 22.30%
Vmpp · Impp 44.77 V · 13.85 A Operating point at max power
Voc · Isc 53.11 V · 14.82 A Sizes the string length
Max system voltage 1500 V Longer strings than 1000 V modules
Dimensions 2376×1128×5 mm · 2.68 m² of roof
Weight 31.0 kg Strong Strong · 1.0 kg below median
Cells 72 Monocrystalline
Coefficient Pmax -0.280 %/°C Strong top 14% of its segment
Coefficient Voc · Isc -0.230 · 0.050 %/°C
NOCT 45 °C At 800 W/m², 20 °C ambient
Product warranty 25 years Hardware defects only
Performance warranty 25 years Weak bottom 10% · median 30 yrs
End-of-warranty output 89.4 % Equals 542 W guaranteed
Degradation 1.00 → 0.40 % First year, then annual

Simulations

Live - change any input
Lifetime output & value
30 years at 1200 kWh/kWp/year and €0.50 per kWh
Power in year 30
-
Lifetime energy
-
Energy value
-

Degradation from this panel's own datasheet figures. No inverter, soiling or shading losses.

Heat losses
-0.280 %/°C against a segment median of -0.300
-
Filter these
Size
Panel Power Eff. Temp. Weight Difference
Longi Solar LGi7-72HTD-620M 620 W 23.10% -0.280 31.0 kg You are here
AIKO-A650-MAE72Mw 650 W 25.20% -0.260 27.0 kg Lighter, +2.1 pp, +5 yr warranty
AIKO-A645-MAE72Mw 645 W 25.00% -0.260 27.0 kg Lighter, +1.9 pp, +5 yr warranty
AIKO-G670-MCH72Mw 670 W 24.80% -0.260 28.2 kg +50 W, +1.7 pp, +5 yr warranty
LR7-72HVHF-670M 670 W 24.80% -0.260 28.5 kg +50 W, +1.7 pp, +5 yr warranty
AIKO-A640-MAE72Mw 640 W 24.80% -0.260 27.0 kg Lighter, +1.7 pp, +5 yr warranty
JKM650-670N-66QL6-BDV (670W class) 670 W 24.80% -0.260 32.5 kg +50 W, +1.7 pp, +5 yr warranty
LR8-66HGD-595M 595 W 22.00% -0.280 32.5 kg -25 W, -1.1 pp, +5 yr warranty
LR7-72HGD-600M 600 W 22.20% -0.280 33.5 kg Heavier, -0.9 pp, +5 yr warranty
600M 600 W 22.40% -0.280 31.0 kg -20 W, -0.7 pp
LR7-72HTH-605M 605 W 22.40% -0.280 28.5 kg -15 W, lighter, -0.7 pp
AIKO-A680-MDE72Mw 680 W 25.20% -0.260 29.0 kg +60 W, +2.1 pp, +5 yr warranty
AIKO-A675-MDE72Mw 675 W 25.00% -0.260 29.0 kg +55 W, +1.9 pp, +5 yr warranty
AIKO-A700-MAE78Dw 700 W 25.00% -0.260 34.5 kg +80 W, +1.9 pp, +5 yr warranty
WST-675BKX72-A2 675 W 25.00% -0.260 32.1 kg +55 W, +1.9 pp, +5 yr warranty
AIKO-A695-MAE78Dw 695 W 24.90% -0.260 34.5 kg +75 W, +1.8 pp, +5 yr warranty

Found 1144 panels of the same or similar size to this one, within ±10 mm. See them here Found 1144 panels of the same or similar size to this one, within ±25 mm. See them here Found 1261 panels of the same or similar size to this one, within ±50 mm. See them here Found 4192 panels of the same or similar size to this one, within ±100 mm. See them here

About the LONGi ROOF 4 series

6 answered

These answers cover the whole series. Where a figure differs, the specification above is this module's own.

What warranty comes with LONGi ROOF 4 panels?
The LONGi ROOF 4 series comes with a 25-year product warranty covering materials and workmanship, plus a 25-year linear power output warranty. LONGi Solar is a Tier 1 manufacturer with a proven financial track record, which provides realistic assurance that warranty claims will be honored for the full 25 years. For a typical residential installation, this secures the investment throughout the entire payback period.
What is HPBC technology and why do LONGi ROOF 4 panels use it?
HPBC (Hybrid Passivated Back Contact) relocates all metal electrical contacts to the rear of the cell, completely eliminating busbars from the front surface. The result is a larger active light-absorbing area and module efficiency reaching 23.1% under STC. Compared to mainstream PERC and TOPCon technologies, ROOF 4 panels deliver more energy from the same roof area, which is critical whenever available mounting space is limited.
Are LONGi ROOF 4 panels a good fit for small or complex roof sections?
Yes, the ROOF 4 series was specifically engineered for this use case. With up to 620 Wp per module and efficiency up to 23.1%, it generates more power from a constrained surface than lower-efficiency alternatives. On roofs broken up by chimneys, dormers, or skylights, every square foot matters, and the ROOF 4 maximizes energy yield from whatever usable area is available.
How do LONGi ROOF 4 panels perform in high summer temperatures?
The ROOF 4 series features exceptional thermal stability with a temperature coefficient of power around -0.28%/°C. This means for every degree Celsius above 25°C, output drops only 0.28% versus the typical 0.35-0.40% seen in older technologies. On hot summer days when module temperatures can exceed 60°C, a ROOF 4 installation produces noticeably more power than systems based on conventional PERC cells.
Do LONGi ROOF 4 panels generate power on overcast days and in low-light conditions?
Yes. The busbar-free HPBC cell design is more responsive to diffuse irradiance, which translates to better output on overcast days, early mornings, and late evenings. Optimized low-light performance is one of the key differentiators of this series versus PERC technology. In climates with limited full-sun hours, this characteristic meaningfully increases the annual kilowatt-hour yield per installed kilowatt of capacity.
Is the all-black look of LONGi ROOF 4 purely aesthetic, or does it affect performance?
The all-black appearance of the ROOF 4 series is a direct result of the HPBC technology, not just a styling choice. Removing metal busbars from the front of the cell eliminates the reflective silver lines visible on conventional panels, creating a uniform deep-black surface. The installation integrates seamlessly into the roofline rather than looking like mounted equipment, all without any efficiency trade-off, since the same innovation that delivers the clean look is also responsible for module efficiency reaching 23.1%.
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