--- title: "Suntech STP655S-D66/Wmh 655W Solar Panel - Specs & Review | ComparePV" description: "Suntech STP655S-D66/Wmh 655W solar panel. Specs: 21.10% efficiency, Monocrystalline cells, dimensions, warranty and temperature coefficient." source: "https://comparepv.com/panel/suntech-stp655s-d66-wmh" updated: 2026-09-11 --- # Suntech STP655S-D66/Wmh Middle of its segment, needs the roof space 249 panels in the segment TOPCon 650-700 W ## Identity - **Manufacturer:** Suntech - **Model:** STP655S-D66/Wmh - **Series:** Ultra X Plus - **Rated power:** 655 W - **Cell technology:** TOPCon ## How it compares Compared against segment TOPCon 650-700 W (249 panels). | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Power (Wp) | 655 W | 665 W | Typical | | | Module efficiency | 21.10% | 22.40% | Weak - bottom 3% | 9,297 | | Power density | 210.9 | 223.7 | Weak - bottom 2% | 9,459 | | Temperature coefficient | -0.340 | -0.290 | Weak - bottom 6% | 8,778 | | Weight (kg) | 33.5 kg | 34.6 kg | Typical | | | Performance warranty | 25 yrs | 30 yrs | Weak - bottom 2% | 9,798 | ### Full peer table | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Module efficiency | 21.10% | 22.40% | Weak - bottom 3% | 9,297 | | Power density | 210.9 | 223.7 | Weak - bottom 2% | 9,459 | | Temperature coefficient | -0.340 | -0.290 | Weak - bottom 6% | 8,778 | | Weight per kWp | 51.1 | 53.2 | Typical | 4,503 | | Performance warranty | 25 yrs | 30 yrs | Weak - bottom 2% | 9,798 | ### Watch out for - **210.9 watts per square metre** - Bottom 2% of the TOPCon 650-700 W segment, against a median of 223.7. Ranked 9,459th in the whole database. - **25 year performance warranty** - Bottom 2% of the TOPCon 650-700 W segment, against a median of 30 yrs. Ranked 9,798th in the whole database. - **21.10% module efficiency** - Bottom 3% of the TOPCon 650-700 W segment, against a median of 22.40%. Ranked 9,297th in the whole database. - **Best for:** Utility-scale and shaded-installations. - **Not ideal for:** Roofs where every square metre has to count, owners who want a long output guarantee and tight roof space. ## Specification ### Electrical - **Rated power (Pmax):** 655 W - **Efficiency:** 21.10 % - **Voltage at Pmax (Vmp):** 37.85 V - **Current at Pmax (Imp):** 17.31 A - **Open-circuit voltage (Voc):** 45.85 V - **Short-circuit current (Isc):** 18.31 A - **Max system voltage:** 1500 V ### Temperature - **Temperature coefficient of Pmax:** -0.340 %/degC - **Temperature coefficient of Voc:** -0.260 %/degC - **Temperature coefficient of Isc:** 0.050 %/degC - **NOCT:** 42 degC ### Cell and construction - **Cell type:** Monocrystalline - **Cell technology:** TOPCon - **Cell count:** 132 ### Physical - **Length:** 2384 mm - **Width:** 1303 mm - **Thickness:** 35 mm - **Weight:** 33.5 kg - **Area:** 3.11 m2 - **Power density:** 210.9 Wp/m2 ### Warranty and degradation - **Product warranty:** 12 years - **Performance warranty:** 25 years - **Output guaranteed at end of warranty:** 84.8 % - **First-year degradation:** 2.00 % - **Annual degradation:** 0.55 % - **Output after 30 years:** 537 W ## Rank in the whole catalogue | Measure | Position | | --- | --- | | Efficiency | 9297 of 14005 | | Power density | 9459 of 14005 | | Temperature coefficient | 8778 of 14005 | | Weight | 4503 of 14005 | | Warranty | 9798 of 14005 | ## About this series Ultra X Plus is a solar panel series built around **210mm monocrystalline silicon cells**, designed for large-scale commercial and industrial installations where every square meter of roof or ground space counts. The use of **PERC technology combined with half-cut and SMBB** cell design helps reduce current losses and improve heat dissipation, allowing the modules to perform reliably even under high temperatures and partial shading. The series is available in both monofacial and **bifacial** configurations, giving investors the flexibility to choose the solution best suited to a specific site and their goal of maximizing energy yield from the rear side of the panel. The large cell format translates into high power density per module, which meaningfully lowers the per-watt cost of the installation (BoS) and shortens installation time for the same panel count. This makes it a solution aimed primarily at installers of solar farms and utility-scale projects seeking high efficiency and lower LCOE without compromising on mechanical durability, confirmed by resistance to heavy snow and wind loads. Ultra X Plus thus combines production scale, proven cell technology, and configuration flexibility in one market-mature series. ## Notable figures - At 21.1% efficiency, this panel is 1.3pp below the \*\*TOPCon 650-700W\*\* median of 22.4% - 210.9 W/m² power density is 12.8 W/m² below \*\*TOPCon 650-700W\*\* median (223.7 W/m²) - requires larger installation area - Temperature coefficient of -0.34%/°C is 0.05pp worse than \*\*TOPCon 650-700W\*\* median (-0.29%/°C) - higher losses in summer heat - 33.5 kg weight - 1.1 kg lighter than \*\*TOPCon 650-700W\*\* median (34.6 kg), reducing installation effort - #9297 for efficiency, #8778 for temperature performance out of 14005 panels ## Questions ### What is the maximum power output of the Suntech Ultra X Plus panel? Panels in the Ultra X Plus series reach a maximum power output of up to 675 Wp. This is achieved through large 210 mm silicon cells combined with half-cut and SMBB technology, which increase power density within the module. As a result, fewer panels are needed to reach the same installed capacity, shortening installation time and reducing mounting structure costs. ### What is TOPCon technology used in the Ultra X Plus, and how does it differ from PERC? TOPCon (Tunnel Oxide Passivated Contact) is a newer-generation cell technology than PERC, used in the Ultra X Plus series. An additional passivation layer on the rear side of the cell reduces carrier recombination, resulting in higher module efficiency and a smaller power loss at high temperatures compared to standard PERC panels. In practice, this means higher energy yield, especially during summer and under high irradiance. ### What warranty comes with Suntech Ultra X Plus panels? The manufacturer provides a 15-year product warranty covering material and workmanship defects, along with a 30-year linear power output warranty. This means the panel must maintain a guaranteed percentage of its initial power throughout its service life, and as a Tier 1 manufacturer, Suntech offers reliable after-sales support for the entire warranty period. ### Is the Suntech Ultra X Plus a bifacial panel? No, this specific variant of the Ultra X Plus series is a monofacial module, generating energy only from the front side. The manufacturer also offers this series in a bifacial version, but choosing between the two depends on the mounting type and site conditions - the monofacial version is best suited for rooftops and installations without reflective ground surfaces. ### Is Suntech a reliable manufacturer, and what does Tier 1 status mean? Suntech is a Chinese manufacturer with Tier 1 status according to BloombergNEF's classification, indicating financial stability, in-house production lines, and a proven track record of supplying modules to large-scale energy projects worldwide. For investors, Tier 1 status matters for bank financing, as lenders and insurers often require Tier 1 panels as a condition for approving project loans. ### Are Ultra X Plus panels suitable for large-scale solar farms? Yes, the Ultra X Plus series was designed for commercial, industrial, and utility-scale installations. The large cell format and power output of up to 675 Wp reduce the number of panels, support structures, and cabling needed for a given installed capacity, directly lowering Balance of System (BoS) costs and the levelized cost of electricity (LCOE). ## Datasheet [Manufacturer datasheet (PDF)](https://comparepv.com/datasheets/STP655-675S-D66-Wmh_EN-d2fba93b23d2.pdf) ## Alternatives | Panel | Power | How it differs | | --- | --- | --- | | [AIKO AIKO-A650-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a650-mae72mw) | 650 W | Cooler, lighter, +4.1 pp | | [AIKO AIKO-A680-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a680-mde72mw) | 680 W | Cooler, +4.1 pp, +5 yr warranty | | [AIKO AIKO-A675-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a675-mde72mw) | 675 W | Cooler, +3.9 pp, +5 yr warranty | | [AIKO AIKO-A645-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a645-mae72mw) | 645 W | Cooler, lighter, +3.9 pp | | [AIKO AIKO-A700-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a700-mae78dw) | 700 W | Cooler, +3.9 pp, +5 yr warranty | | [AIKO AIKO-A695-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a695-mae78dw) | 695 W | Cooler, +3.8 pp, +5 yr warranty | | [AIKO AIKO-G670-MCH72Mw](https://comparepv.com/panel/aiko-aiko-g670-mch72mw) | 670 W | Cooler, lighter, +3.7 pp | | [Suntech STP650S-D66/Pmh+](https://comparepv.com/panel/wuxi-suntech-power-co-ltd-stp650s-d66-pmh) | 650 W | Heavier, -0.2 pp, +5 yr warranty | | [Suntech STP660S-D66/Wmh](https://comparepv.com/panel/suntech-stp660s-d66-wmh) | 660 W | Very close match | | [Suntech STP665S-D66/Wmh](https://comparepv.com/panel/suntech-stp665s-d66-wmh) | 665 W | +10 W, +0.3 pp | | [Suntech STP670S-D66/Wmh](https://comparepv.com/panel/suntech-stp670s-d66-wmh) | 670 W | +15 W, +0.5 pp | | [Suntech STP675S-D66/Wmh](https://comparepv.com/panel/suntech-stp675s-d66-wmh) | 675 W | +20 W, +0.6 pp | | [AIKO AIKO-A805-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a805-grh78dw) | 805 W | +150 W, cooler, +4.0 pp | | [AIKO AIKO-A800-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a800-grh78dw) | 800 W | +145 W, cooler, +3.8 pp | | [AIKO AIKO-A795-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a795-grh78dw) | 795 W | +140 W, cooler, +3.7 pp | | [AIKO AIKO-A790-GRH78Dw](https://comparepv.com/panel/aiko-aiko-a790-grh78dw) | 790 W | +135 W, cooler, +3.5 pp | --- Source: https://comparepv.com/panel/suntech-stp655s-d66-wmh Not in this file, on the page: a thirty-year output simulator and alternatives filtered by how closely they match these dimensions.