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Longi Solar 615M
Longi Solar Brand review

615M

615 Wp Monocrystalline
ComparePV verdict

Strong in heat, short guarantee

Rank 1,620 of 14,129
Compare panels Datasheet PDF
Power (Wp)
615
Typical for its class
Efficiency (%)
22.90
Strong · top 22%
Density (Wp/m²)
229.5
Strong · top 21%
Temp (%/°C)
-0.280
Strong · top 14%
Weight (kg)
31.0
Typical · median 32.0 kg
Warranty (yrs)
25
Weak · bottom 10%

Longi Solar ROOF 4 series was designed with the goal of maximizing roof space utilization and providing stable energy production in both domestic and commercial installations. Its key feature is the combination of monocrystalline PERC cells with half-cut technology, which in practice helps reduce power losses under everyday operating conditions - when partial shading, dirt, or uneven irradiance across roof sections occurs. The application of modern connection architecture in the module supports higher reliability and more predictable yields over the long term, which is appreciated by those planning long-term investments.

ROOF 4 series is also focused on easier installation design - the modules are compatible with popular inverters and optimizer solutions, making integration into typical rooftop systems less problematic. For investors, the all-black aesthetic is also important, especially in projects for single-family homes. Compared to many competitive rooftop modules, ROOF 4 emphasizes practical usability in real conditions rather than just catalog specifications.

Ranking

6,088 panels in the 515-715 W band, all technologies
Metric This panel Median Position in segment Overall rank
Module efficiency 22.90% 22.30% Strong · top 22% 2,412
Power density 229.5 222.6 Strong · top 21% 2,367
Temperature coefficient -0.280 -0.300 Strong · top 14% 1,347
Weight per kWp 50.4 53.0 Typical 3,802
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

8 positive · 3 caution
Best for

Residential, commercial and shaded-installations.

Not ideal for

Owners who want a long output guarantee.

Strengths
-0.280 %/°C temperature coefficient

Top 14% of the 515-715 W band, against a median of -0.300.

229.5 watts per square metre

Top 21% of the 515-715 W band, against a median of 222.6.

22.90% module efficiency

Top 22% of the 515-715 W band, against a median of 22.30%.

Watch-outs
25 year performance warranty

Bottom 10% of the 515-715 W band, against a median of 30 yrs.

What owners get
Half-cut PERC reduces shading losses

The combination of monocrystalline PERC cells with half-cut technology meaningfully reduces power losses under partial shading, soiling, or uneven roof irradiance, while also lowering hot-spot risk due to reduced current per half-cell.

Tier-1 bankable manufacturer, founded 2000

Longi Solar is a Tier-1, bankable manufacturer founded in 2000 and one of the world's largest silicon wafer suppliers, which simplifies project financing through banks and funds and reduces long-term service-continuity risk.

Dual 25-year warranty

The series carries a 25-year product warranty plus a 25-year linear power warranty (typically ~84.8% power retention after 25 years), matching the standard offered by comparable PERC modules in this power class.

22.4-23.1% efficiency, in line with peers

Module efficiency of 22.4-23.1% at 600-620 Wp is comparable to peer products such as HT-SAAE HT66-18X(ND)-F (23%) and Weran Solar LR7-72HTH (23%), placing the series mid-pack among the highest-power rooftop modules currently on the market.

All-black aesthetics and easy system integration

The all-black variant is a key selling point for single-family home projects, and compatibility with popular inverters and power optimizers simplifies design for typical rooftop installations without extra component certification.

Trade-offs
No bifacial variant

Unlike the comparable MY Solar G&A N-Type TOPCon Bifacial (620 Wp, 22.95%) in the same power and efficiency range, the ROOF 4 series lacks a dual-sided option, forgoing potential rear-side yield gains (typically a few to over ten percent depending on albedo and mounting) that competitors already offer.

PERC instead of N-type TOPCon

PERC cells represent an older cell technology generation compared to N-type TOPCon, used by part of the competition in this power class (e.g., MY Solar). TOPCon typically has lower LID/LeTID degradation and a better power temperature coefficient (about -0.30%/°C vs. roughly -0.35%/°C typical for PERC in this series), translating into higher yield in hot climates and over long-term operation.

Notes from the database
  • Efficiency of 22.9% is 1.1pp above the database median (21.8%)
  • Power density of 229.5 W/m² packs 11.4 W/m² more into the same footprint vs database median (218.1 W/m²)
  • At -0.28%/°C, hot weather performance is typical for database panels
  • At 31.0 kg (4.5 kg above database median of 26.5 kg), requires checking roof load capacity
  • In the top 17% for efficiency among all N-type panels

Specifications

Open datasheet PDF
Nominal power (Pmax) 615 Wp Nameplate at 1000 W/m², 25 °C
Module efficiency 22.90 % Strong Segment median 22.30%
Vmpp · Impp 44.63 V · 13.78 A Operating point at max power
Voc · Isc 52.96 V · 14.75 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 Typical Typical · median 32.0 kg
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
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 615M 615 W 22.90% -0.280 31.0 kg You are here
AIKO-A650-MAE72Mw 650 W 25.20% -0.260 27.0 kg Lighter, +2.3 pp, +5 yr warranty
AIKO-A645-MAE72Mw 645 W 25.00% -0.260 27.0 kg Lighter, +2.1 pp, +5 yr warranty
AIKO-A640-MAE72Mw 640 W 24.80% -0.260 27.0 kg Lighter, +1.9 pp, +5 yr warranty
LR8-66HVD-665M 665 W 24.62% -0.260 33.5 kg +50 W, +1.7 pp, +5 yr warranty
JKM650-670N-66QL6-BDV (665W class) 665 W 24.62% -0.260 32.5 kg +50 W, +1.7 pp, +5 yr warranty
HY665-B144DSS 665 W 24.62% -0.260 27.6 kg +50 W, +1.7 pp, +5 yr warranty
SPDG665-BC132R12 665 W 24.62% -0.260 33.5 kg +50 W, +1.7 pp, +5 yr warranty
LR8-66HGD-595M 595 W 22.00% -0.280 32.5 kg -20 W, -0.9 pp, +5 yr warranty
LR7-72HGD-600M 600 W 22.20% -0.280 33.5 kg Heavier, -0.7 pp, +5 yr warranty
600M 600 W 22.40% -0.280 31.0 kg -15 W, -0.5 pp
LR7-72HTH-605M 605 W 22.40% -0.280 28.5 kg -10 W, lighter, -0.5 pp
AIKO-A680-MDE72Mw 680 W 25.20% -0.260 29.0 kg +65 W, +2.3 pp, +5 yr warranty
AIKO-A675-MDE72Mw 675 W 25.00% -0.260 29.0 kg +60 W, +2.1 pp, +5 yr warranty
AIKO-A700-MAE78Dw 700 W 25.00% -0.260 34.5 kg +85 W, +2.1 pp, +5 yr warranty
WST-675BKX72-A2 675 W 25.00% -0.260 32.1 kg +60 W, +2.1 pp, +5 yr warranty
AIKO-A695-MAE78Dw 695 W 24.90% -0.260 34.5 kg +80 W, +2.0 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 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 does the Longi Solar ROOF 4 series come with?
The ROOF 4 series carries a dual 25-year warranty: a 25-year product warranty covering manufacturing defects and physical damage, and a 25-year linear power output warranty protecting against excessive degradation over the system's lifetime. As a Tier 1 manufacturer with an established European distribution network, Longi Solar provides reliable warranty support throughout the entire coverage period.
What is half-cut PERC technology and why does it matter for the ROOF 4 series?
Half-cut technology splits each solar cell in two, reducing internal resistance and limiting power losses caused by partial shading from chimneys, dormers, or nearby trees. PERC (Passivated Emitter and Rear Cell) adds rear-surface passivation to boost conversion efficiency. In practice, the ROOF 4 series handles uneven irradiance better than conventional full-cell modules, which is especially valuable on residential pitched roofs.
Are Longi Solar ROOF 4 panels suitable for a pitched residential roof?
Yes, the ROOF 4 series is designed primarily for prosumer and residential pitched-roof installations. Modules mount on standard rail systems at roof pitches of roughly 15-60°. A peak output of up to 620 Wp per panel reduces the number of modules required, saving valuable roof space, while the all-black variant blends seamlessly with dark roof tiles for a clean aesthetic.
Is the Longi Solar ROOF 4 series available in an all-black version?
Yes, Longi Solar offers an all-black variant of the ROOF 4 series featuring a black frame and black backsheet. This option is particularly popular in modern single-family home projects where rooftop aesthetics are a priority. It is worth noting that the dark backsheet can slightly raise the module's operating temperature on hot days, an effect the manufacturer accounts for in the published specifications.
Are ROOF 4 panels compatible with popular inverters and power optimizers?
Yes, the ROOF 4 series is compatible with widely used single-phase and three-phase string inverters - including Fronius, SMA, Huawei, and Solis - as well as optimizer solutions such as SolarEdge and Tigo. Standard MC4 connectors and conventional MPPT voltage ranges mean no special BoS components are needed, simplifying system design and integration into existing photovoltaic installations.
How does the Longi Solar ROOF 4 series perform under cloudy conditions or partial shading?
The half-cut cell architecture splits the module into two electrically independent halves, limiting the impact of localized shading on overall energy yield. Combined with PERC cells and a low temperature coefficient, the ROOF 4 series outperforms older full-cell modules under the variable irradiance conditions typical of Central European climates. A peak power of up to 620 Wp per panel further offsets losses during periods of reduced insolation.
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