--- title: "Solarspace SS9-66HD-645M 645W Solar Panel - Specs & Review | ComparePV" description: "Solarspace SS9-66HD-645M 645W solar panel. Specs: 20.76% efficiency, Monocrystalline cells, dimensions, warranty and temperature coefficient." source: "https://comparepv.com/panel/solarspace-ss9-66hd-645m" updated: 2026-09-11 --- # Solarspace SS9-66HD-645M Strong in heat, modest efficiency 217 panels in the segment PERC 600-650 W ## Identity - **Manufacturer:** Solarspace - **Model:** SS9-66HD-645M - **Series:** SS9-66HD 645-670M - **Rated power:** 645 W - **Cell technology:** PERC - **Bifacial:** yes ## How it compares Compared against segment PERC 600-650 W (217 panels). | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Power (Wp) | 645 W | 605 W | Strong - top 7% | | | Module efficiency | 20.76% | 21.38% | Weak - bottom 11% | 10,612 | | Power density | 207.6 | 213.8 | Weak - bottom 12% | 10,562 | | Temperature coefficient | -0.330 | -0.340 | Strong - top 6% | 8,545 | | Weight (kg) | 37.5 kg | 34.0 kg | Typical | | | Performance warranty | 30 yrs | 30 yrs | Typical | 21 | ### Full peer table | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Module efficiency | 20.76% | 21.38% | Weak - bottom 11% | 10,612 | | Power density | 207.6 | 213.8 | Weak - bottom 12% | 10,562 | | Temperature coefficient | -0.330 | -0.340 | Strong - top 6% | 8,545 | | Weight per kWp | 58.1 | 55.7 | Typical | 11,573 | | Performance warranty | 30 yrs | 30 yrs | Typical | 21 | ### Strengths - **-0.330 %/°C temperature coefficient** - Top 6% of the PERC 600-650 W segment, against a median of -0.340. Ranked 8,545th in the whole database. ### Watch out for - **20.76% module efficiency** - Bottom 11% of the PERC 600-650 W segment, against a median of 21.38%. - **207.6 watts per square metre** - Bottom 12% of the PERC 600-650 W segment, against a median of 213.8. - **Best for:** Commercial, utility-scale and shaded-installations. - **Not ideal for:** Tight roof space and roofs where every square metre has to count. ## Specification ### Electrical - **Rated power (Pmax):** 645 W - **Efficiency:** 20.76 % - **Voltage at Pmax (Vmp):** 37.71 V - **Current at Pmax (Imp):** 17.11 A - **Open-circuit voltage (Voc):** 45.31 V - **Short-circuit current (Isc):** 18.11 A - **Max system voltage:** 1500 V ### Temperature - **Temperature coefficient of Pmax:** -0.330 %/degC - **Temperature coefficient of Voc:** -0.260 %/degC - **Temperature coefficient of Isc:** 0.046 %/degC - **NOCT:** 45 degC ### Cell and construction - **Cell type:** Monocrystalline - **Cell technology:** PERC - **Cell count:** 132 - **Bifacial:** yes ### Physical - **Length:** 2384 mm - **Width:** 1303 mm - **Thickness:** 33 mm - **Weight:** 37.5 kg - **Area:** 3.11 m2 - **Power density:** 207.6 Wp/m2 ### Warranty and degradation - **Product warranty:** 15 years - **Performance warranty:** 30 years - **Output guaranteed at end of warranty:** 85.0 % - **First-year degradation:** 2.00 % - **Annual degradation:** 0.45 % - **Output after 30 years:** 548 W ## Rank in the whole catalogue | Measure | Position | | --- | --- | | Efficiency | 10612 of 14005 | | Power density | 10562 of 14005 | | Temperature coefficient | 8545 of 14005 | | Weight | 11573 of 14005 | | Warranty | 21 of 14005 | ## About this series The Solarspace SS9-66HD 645-670M series are large-format modules designed to maximize energy yield from a limited surface area and ensure stable operation in demanding conditions. The use of **bifacial construction** allows for a real increase in energy production by utilizing reflected light from the ground - which works particularly well on roofs with light-colored membranes, carports, and ground-mounted installations. The **half-cut architecture** also deserves attention, as it reduces losses at connections and improves the module's performance under partial shading - a common scenario, for example, along the edges of roofs, chimneys, or rows of structures. Another distinguishing feature is the **anti-reflective glass coating**, which supports efficient radiation collection in less favorable lighting conditions. This is a good choice for investors who value not only high yield but also predictability - this is facilitated by the **long linear power warranty** and a robust, weather-resistant construction with a sealed connection box. The SS9-66HD series is aimed at C&I and PV farm projects, where performance from each module and ease of scalability are key. ## Notable figures - At 20.8% efficiency, this panel is 0.6pp below the \*\*PERC 600-650W\*\* median of 21.4% - 207.6 W/m² power density is 6.2 W/m² below \*\*PERC 600-650W\*\* median (213.8 W/m²) - requires larger installation area - Temperature coefficient of -0.33%/°C matches the \*\*PERC 600-650W\*\* median - At 37.5 kg, this panel is 3.5 kg heavier than the \*\*PERC 600-650W\*\* median (34.0 kg) - more demanding for installation crews - 70% bifaciality enables rear-side power generation, boosting yield by 4-10% on reflective surfaces ## Questions ### What warranties come with the Solarspace SS9-66HD 645-670M modules? The SS9-66HD 645-670M series carries a 15-year product warranty covering material defects and workmanship, plus a 30-year linear power warranty. A linear power warranty means degradation is spread evenly over time, so the module retains a significant portion of its rated output after three decades. This is one of the longer warranty standards available in the commercial PERC module segment. ### What does bifacial mean for the SS9-66HD 645-670M and where does it make sense? Bifacial means the module generates power from both sides — the front absorbs direct irradiance, while the rear captures light reflected off the ground or surface below. In the SS9-66HD 645-670M, this translates to measurable energy gains wherever ground albedo is high: white roofing membranes, gravel, concrete, or grass on ground-mount farms. On typical dark bituminous roofs, the rear-side gain is negligible. ### Are the Solarspace SS9-66HD 645-670M panels suitable for ground-mount utility or C&I farms? Yes, the SS9-66HD 645-670M series is designed primarily for C&I and utility-scale PV projects. High peak power up to 670 Wp reduces the total module count and shortens installation time. The bifacial design pairs well with high-albedo ground surfaces, and the large format is well suited to tracker or fixed-tilt ground-mount structures where scaling efficiency matters. ### How do the SS9-66HD 645-670M modules handle partial shading? The half-cut cell architecture splits each PERC cell into two halves, reducing resistive losses and limiting the impact of localized shading — from roof edges, chimneys, or inter-row shading on farms. It does not eliminate shading losses entirely, but ensures that a shaded portion of the module has less effect on the performance of the remaining cells in the string. ### How heavy are the SS9-66HD 645-670M modules and are they difficult to install? Modules in the SS9-66HD 645-670M series fall into the large-format category — estimated weight is approximately 37–38 kg with dimensions close to 2384×1303 mm. These are standard dimensions for the 660–670 Wp commercial class. Rooftop installation requires at least two technicians; for ground-mount farms these parameters are completely typical and pose no logistical challenge. ### Is PERC technology in the SS9-66HD 645-670M outdated compared to TOPCon or HJT? Bifacial half-cut PERC still delivers a strong price-to-yield ratio in the commercial segment. TOPCon and HJT achieve higher efficiency and a better temperature coefficient, but at a higher upfront cost. For PV farms and C&I projects where LCOE is the primary metric, 645–670 Wp PERC modules remain a competitive choice — especially from a Tier 1 manufacturer like Solarspace. ## Datasheet [Manufacturer datasheet (PDF)](https://comparepv.com/datasheets/ss9-66hd-m-8ce85e4765da.pdf) ## Alternatives | Panel | Power | How it differs | | --- | --- | --- | | [AIKO AIKO-A650-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a650-mae72mw) | 650 W | Cooler, lighter, +4.4 pp | | [AIKO AIKO-A680-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a680-mde72mw) | 680 W | Cooler, lighter, +4.4 pp | | [AIKO AIKO-A675-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a675-mde72mw) | 675 W | Cooler, lighter, +4.2 pp | | [AIKO AIKO-A645-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a645-mae72mw) | 645 W | Cooler, lighter, +4.2 pp | | [AIKO AIKO-A695-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a695-mae78dw) | 695 W | +50 W, cooler, +4.1 pp | | [AIKO AIKO-G670-MCH72Mw](https://comparepv.com/panel/aiko-aiko-g670-mch72mw) | 670 W | Cooler, lighter, +4.0 pp | | [Longi Solar LR7-72HVHF-670M](https://comparepv.com/panel/longi-lr7-72hvhf-670m) | 670 W | Cooler, lighter, +4.0 pp | | [Solarspace SS9-66HD-650M](https://comparepv.com/panel/solarspace-ss9-66hd-650m) | 650 W | Very close match | | [Solarspace SS9-66HD-655M](https://comparepv.com/panel/solarspace-ss9-66hd-655m) | 655 W | +10 W, +0.3 pp | | [Solarspace SS9-66HD-660M](https://comparepv.com/panel/solarspace-ss9-66hd-660m) | 660 W | +15 W, +0.5 pp | | [Solarspace SS9-66HD-665M](https://comparepv.com/panel/solarspace-ss9-66hd-665m) | 665 W | +20 W, +0.6 pp | | [Solarspace SS9-66HD-670M](https://comparepv.com/panel/solarspace-ss9-66hd-670m) | 670 W | +25 W, +0.8 pp | | [Solarspace SS9-66HD-675N](https://comparepv.com/panel/solarspace-ss9-66hd-675n) | 675 W | +30 W, cooler, +1.0 pp | | [Solarspace SS9-66HD-680N](https://comparepv.com/panel/solarspace-ss9-66hd-680n) | 680 W | +35 W, cooler, +1.1 pp | | [Solarspace SS9-66HD-685N](https://comparepv.com/panel/solarspace-ss9-66hd-685n) | 685 W | +40 W, cooler, +1.3 pp | | [AIKO AIKO-A805-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a805-grh78dw) | 805 W | +160 W, cooler, +4.3 pp | --- Source: https://comparepv.com/panel/solarspace-ss9-66hd-645m Not in this file, on the page: a thirty-year output simulator, a bifacial gain calculator and alternatives filtered by how closely they match these dimensions.