--- title: "GCL GCL-M12/66H-665W 665W Solar Panel - Specs & Review | ComparePV" description: "GCL GCL-M12/66H-665W 665W solar panel. Specs: 21.40% efficiency, Monocrystalline cells, dimensions, warranty and temperature coefficient." source: "https://comparepv.com/panel/gcl-gcl-m12-66h-665w" updated: 2026-09-11 --- # GCL GCL-M12/66H-665W Middle of its segment, weak in heat 320 panels in the segment PERC 650-700 W ## Identity - **Manufacturer:** GCL - **Model:** GCL-M12/66H-665W - **Series:** GCL-M12/66H - **Rated power:** 665 W - **Cell technology:** PERC ## How it compares Compared against segment PERC 650-700 W (320 panels). | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Power (Wp) | 665 W | 660 W | Typical | | | Module efficiency | 21.40% | 21.25% | Typical | 8,323 | | Power density | 214.1 | 212.5 | Typical | 8,250 | | Temperature coefficient | -0.350 | -0.340 | Weak - bottom 10% | 10,419 | | Weight (kg) | 34.2 kg | 34.5 kg | Typical | | | Performance warranty | 25 yrs | 30 yrs | Weak - bottom 21% | 9,798 | ### Full peer table | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Module efficiency | 21.40% | 21.25% | Typical | 8,323 | | Power density | 214.1 | 212.5 | Typical | 8,250 | | Temperature coefficient | -0.350 | -0.340 | Weak - bottom 10% | 10,419 | | Weight per kWp | 51.4 | 52.3 | Typical | 4,818 | | Performance warranty | 25 yrs | 30 yrs | Weak - bottom 21% | 9,798 | ### Watch out for - **-0.350 %/°C temperature coefficient** - Bottom 10% of the PERC 650-700 W segment, against a median of -0.340. - **25 year performance warranty** - Bottom 21% of the PERC 650-700 W segment, against a median of 30 yrs. - **Best for:** Utility-scale, commercial and shaded-installations. - **Not ideal for:** Hot climates and owners who want a long output guarantee. ## Specification ### Electrical - **Rated power (Pmax):** 665 W - **Efficiency:** 21.40 % - **Voltage at Pmax (Vmp):** 38.00 V - **Current at Pmax (Imp):** 17.50 A - **Open-circuit voltage (Voc):** 45.80 V - **Short-circuit current (Isc):** 18.60 A - **Max system voltage:** 1500 V ### Temperature - **Temperature coefficient of Pmax:** -0.350 %/degC - **Temperature coefficient of Voc:** -0.280 %/degC - **Temperature coefficient of Isc:** 0.050 %/degC - **NOCT:** 45 degC ### Cell and construction - **Cell type:** Monocrystalline - **Cell technology:** PERC - **Cell count:** 132 ### Physical - **Length:** 2384 mm - **Width:** 1303 mm - **Thickness:** 35 mm - **Weight:** 34.2 kg - **Area:** 3.11 m2 - **Power density:** 214.1 Wp/m2 ### Warranty and degradation - **Product warranty:** 12 years - **Performance warranty:** 25 years - **Annual degradation:** 0.55 % - **Output after 30 years:** 552 W ## Rank in the whole catalogue | Measure | Position | | --- | --- | | Efficiency | 8323 of 14005 | | Power density | 8250 of 14005 | | Temperature coefficient | 10419 of 14005 | | Weight | 4818 of 14005 | | Warranty | 9798 of 14005 | ## Pros - **Long-standing BNEF Tier 1 status – bankability assurance** - GCL-SI has maintained continuous BNEF Tier 1 listing for several consecutive years (confirmed by PV Magazine and RenewEconomy), enabling non-recourse project financing for utility-scale PV farms and reducing risk exposure for lending institutions. - **210 mm large-format wafer + 132 half-cut cells** - The 132 half-cut cell configuration on a 210 mm wafer delivers higher per-module output (660–680 Wp) and lower BoS costs: fewer racking components, less cabling, and reduced installation labor per kWp in commercial and ground-mount applications. - **Non-destructive cutting – reduced microfracture risk** - The non-destructive cutting technique minimizes mechanical stress on cells during manufacturing, lowering the risk of performance degradation caused by microcracks (EL defects) over the system's service life — particularly relevant for long-distance shipping and installations subject to high wind or snow loads. - **PID resistance backed by third-party certification** - The module has passed IEC 61701 (salt mist corrosion), IEC 62716 (ammonia resistance), and DIN EN 60068-2-68 (sand and dust) testing, qualifying it for deployment in demanding environments such as coastal zones and industrial sites. - **Efficiency on par with PERC peers** - The 21.2–21.9% efficiency range positions this series at the same level as direct PERC-class competitors (SpolarPV SPV680: 21.92%; Solaria SPVxxx: 21.92%), while also offering the added credibility of a Tier 1 manufacturer with a longer market track record. ## Cons - **P-type PERC – a technology losing market ground** - At the same power class (680 Wp), the competing AIKO Comet 3N72 achieves 25.2% efficiency using N-type ABC technology — an absolute advantage of 3.3 percentage points over the GCL-M12/66H series' maximum of 21.9%. PERC also exhibits higher LID degradation rates during the initial months of operation compared to N-type, which may translate into lower cumulative energy yield over the long term. - **Monofacial only – no bifacial gain** - The series does not offer a bifacial variant (is\_bifacial: false), whereas many competing modules in this power class (e.g., GCL-M12/66GDF) can capture an additional 5–25% yield from rear-side albedo reflection. In ground-mount installations over light-colored soil or grass, this represents a tangible loss in energy production potential. - **12-year product warranty – below premium-tier standard** - The product warranty stands at 12 years, while premium manufacturers (LONGi Hi-MO X6, JA Solar DeepBlue 4.0 Pro) routinely offer 15 years as standard. For commercial projects financed over 15+ years, this gap may become a procurement disadvantage or necessitate additional equipment insurance coverage. ## About this series GCL GCL-M12/66H series feature large-size, half-cell technology, designed with the aim of maximizing energy yield in installations where the cost of energy throughout the entire life cycle is crucial. The application of **P-type PERC monocrystalline cell technology** and **dense packing** translates to better surface utilization and more predictable energy production under typical operating conditions. A key advantage of this series is its approach to operational risks - **non-destructive cutting** reduces susceptibility to micro-cracking, while refined material selection and processes support **resistance to PID**, helping maintain performance over time. The glass-backsheet construction facilitates integration with common mounting systems, and the module format helps reduce the costs of auxiliary equipment for farms (less construction, cabling, and installation work per unit of power). This is an excellent choice for projects where operational profitability and reliability are prioritized-particularly for ground-mounted installations, large industrial rooftops, and investments focused on stable returns. ## Notable figures - Efficiency of 21.4% matches the \*\*PERC 650-700W\*\* median - Power density of 214.1 W/m² matches the \*\*PERC 650-700W\*\* median - Temperature coefficient of -0.35%/°C matches the \*\*PERC 650-700W\*\* median - Ranked #8323 out of 14005 panels for efficiency in the database ## Questions ### What warranty does the GCL-M12/66H series carry and what does it specifically cover? The GCL-M12/66H series is backed by a 12-year product warranty covering material and workmanship defects, along with a 25-year linear power output warranty. The manufacturer guarantees that after 25 years of operation the module will retain at least 84.8% of its nominal rated power. For installations targeting long-term return on investment, this is one of the key parameters worth comparing across product series. ### What do PERC and half-cut technologies mean in the GCL-M12/66H series and why do they matter? PERC (Passivated Emitter and Rear Cell) incorporates a reflective passivation layer on the rear side of the cell, allowing photons that would otherwise pass through unconverted to be captured for a second conversion pass — the result is higher efficiency without a sharp increase in manufacturing cost. Half-cut technology, which splits each cell into two halves, reduces resistive losses and limits the impact of partial shading on the module's overall power output. GCL additionally applies non-destructive cutting, which minimizes the risk of microcracks during transportation and long-term operation. ### How much does a GCL-M12/66H panel weigh and is it suitable for large industrial rooftops? The module weighs approximately 34 kg and has dimensions of 2384 × 1303 × 35 mm. When planning installations on industrial or warehouse rooftops, this load must be factored into the structural design. The large module format delivers a clear BoS cost advantage — fewer mounting rails, connectors, and cables are required per unit of power, which typically lowers the overall installed cost for large-scale rooftop systems. ### Are GCL-M12/66H panels resistant to PID and what does that mean in practice? Yes, the GCL-M12/66H series is engineered with high resistance to Potential-Induced Degradation (PID). PID manifests as a progressive loss of module power output in systems where panels operate at high voltage relative to ground — a particularly critical issue in large utility-scale plants and long string configurations. Optimized encapsulant materials and tightly controlled manufacturing processes mitigate this effect, resulting in more stable energy yield over the full operational lifetime. ### Is the GCL-M12/66H panel bifacial and can it be mounted on a white-surface racking system to generate additional energy? No, the GCL-M12/66H series is a monofacial module in a glass-backsheet construction. It does not generate power from light reflected off the ground or underlying surface. If bifacial gain from albedo reflectance is a priority, you should consider other GCL series available in the GDF (glass-glass bifacial) variant. For typical ground-mount and rooftop installations without a dedicated high-reflectivity surface, the absence of bifacial capability is not a significant drawback. ### How do GCL-M12/66H panels perform at high temperatures during summer? The temperature coefficient of maximum power (Pmax) for this series is approximately −0.35%/°C. This means that for every degree Celsius above the STC reference temperature of 25°C, the module loses approximately 0.35% of its rated power. At a cell operating temperature of, for example, 65°C on a hot summer day, the power loss is approximately 14%. This is a typical result for P-type PERC cells — lower than older cell technologies, though N-type cells (TOPCon, HJT) achieve better coefficients in this regard. This figure should be taken into account when running annual energy yield simulations. ## Datasheet [Manufacturer datasheet (PDF)](https://comparepv.com/datasheets/EN-M1266H-H0-23c924aa4b0d.pdf) ## Alternatives | Panel | Power | How it differs | | --- | --- | --- | | [AIKO AIKO-A650-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a650-mae72mw) | 650 W | Cooler, lighter, +3.8 pp | | [AIKO AIKO-A680-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a680-mde72mw) | 680 W | Cooler, lighter, +3.8 pp | | [AIKO AIKO-A675-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a675-mde72mw) | 675 W | Cooler, lighter, +3.6 pp | | [AIKO AIKO-A645-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a645-mae72mw) | 645 W | Cooler, lighter, +3.6 pp | | [AIKO AIKO-A700-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a700-mae78dw) | 700 W | Cooler, +3.6 pp, +5 yr warranty | | [AIKO AIKO-A695-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a695-mae78dw) | 695 W | Cooler, +3.5 pp, +5 yr warranty | | [AIKO AIKO-G670-MCH72Mw](https://comparepv.com/panel/aiko-aiko-g670-mch72mw) | 670 W | Cooler, lighter, +3.4 pp | | [GCL GCL-M12/66GDF-655W](https://comparepv.com/panel/gcl-gcl-m12-66gdf-655w) | 655 W | Heavier, -0.3 pp, +5 yr warranty | | [GCL GCL-M12/66H-660W](https://comparepv.com/panel/gcl-gcl-m12-66h-660w) | 660 W | Very close match | | [AIKO AIKO-A805-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a805-grh78dw) | 805 W | +140 W, cooler, +3.7 pp | | [AIKO AIKO-A800-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a800-grh78dw) | 800 W | +135 W, cooler, +3.5 pp | | [AIKO AIKO-A795-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a795-grh78dw) | 795 W | +130 W, cooler, +3.4 pp | | [AIKO AIKO-A790-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a790-grh78dw) | 790 W | +125 W, cooler, +3.2 pp | | [Trina Solar TSM-NEG21C.20Q-760](https://comparepv.com/panel/trina-solar-tsm-neg21c-20q-760) | 760 W | +95 W, cooler, +3.1 pp | | [AIKO AIKO-A785-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a785-grh78dw) | 785 W | +120 W, cooler, +3.0 pp | | [Gokin GK-4-78HGBD-780M](https://comparepv.com/panel/gokin-gk-4-78hgbd-780m) | 780 W | +115 W, cooler, +2.9 pp | --- Source: https://comparepv.com/panel/gcl-gcl-m12-66h-665w Not in this file, on the page: a thirty-year output simulator and alternatives filtered by how closely they match these dimensions.