--- title: "Suntech STP670S-D66/Wmh vs Suntech STP660S-D66/Pmh+ - Solar Panel Comparison | ComparePV" description: "Compare Suntech STP670S-D66/Wmh vs Suntech STP660S-D66/Pmh+ side by side: what actually differs, output when it is hot, thirty-year production, and the full specification." source: "https://comparepv.com/compare/suntech-stp670s-d66-wmh/wuxi-suntech-power-co-ltd-stp660s-d66-pmh" updated: 2026-09-11 --- # Suntech STP670S-D66/Wmh vs Suntech STP660S-D66/Pmh+ 9 differences, and they point both ways The largest is performance warranty: 5 yrs longer. 10 of 19 comparable parameters are identical. ## The two panels | Attribute | A | B | | --- | --- | --- | | Panel | [Suntech STP670S-D66/Wmh](https://comparepv.com/panel/suntech-stp670s-d66-wmh) | [Suntech STP660S-D66/Pmh+](https://comparepv.com/panel/wuxi-suntech-power-co-ltd-stp660s-d66-pmh) | | Manufacturer | Suntech | Suntech | | Power | 670 Wp | 660 Wp | | Efficiency | 21.60 % | 21.20 % | | Technology | TOPCon | TOPCon | ## Where they differ Ranked by how much the difference matters, not by datasheet order. | Parameter | STP670S-D66/Wmh | STP660S-D66/Pmh+ | Difference | | --- | --- | --- | --- | | Performance warranty | 25 yrs | 30 yrs | +5 yrs for STP660S-D66/Pmh+ | | Weight | 33.5 kg | 37.5 kg | -4.0 kg for STP670S-D66/Wmh | | Weight per kWp | 50.0 kg/kWp | 56.8 kg/kWp | -6.8 kg/kWp for STP670S-D66/Wmh | | Module efficiency | 21.60 % | 21.20 % | +0.40 pp for STP670S-D66/Wmh | | Product warranty | 12 yrs | 15 yrs | +3 yrs for STP660S-D66/Pmh+ | | Annual degradation | 0.55 %/yr | 0.45 %/yr | -0.10 %/yr for STP660S-D66/Pmh+ | | Power density | 215.7 Wp/m² | 212.5 Wp/m² | +3.2 Wp/m² for STP670S-D66/Wmh | | Rated power | 670 Wp | 660 Wp | +10 W for STP670S-D66/Wmh | | Bifacial | No | Yes | No vs Yes | ## Every compared parameter | Parameter | STP670S-D66/Wmh | STP660S-D66/Pmh+ | | --- | --- | --- | | Rated power | 670 Wp | 660 Wp | | Module efficiency | 21.60 % | 21.20 % | | Power density | 215.7 Wp/m² | 212.5 Wp/m² | | Open-circuit voltage | 46.45 V | 46.05 V | | Voltage at max power | 38.45 V | 38.05 V | | Short-circuit current | 18.43 A | 18.35 A | | Current at max power | 17.43 A | 17.35 A | | Temperature coefficient | -0.340 %/°C | -0.340 %/°C | | Dimensions | 2384x1303x35 mm | 2384x1303x35 mm | | Module area | 3.106 m² | 3.106 m² | | Weight | 33.5 kg | 37.5 kg | | Weight per kWp | 50.0 kg/kWp | 56.8 kg/kWp | | Product warranty | 12 yrs | 15 yrs | | Performance warranty | 25 yrs | 30 yrs | | Annual degradation | 0.55 %/yr | 0.45 %/yr | | Cell technology | TOPCon | TOPCon | | Cell type | Monocrystalline | Monocrystalline | | Cell count | 132 | 132 | | Bifacial | No | Yes | ## Thirty-year yield Each panel's own declared degradation curve, at 1,200 kWh/kWp a year Same temp coeff. for both panels (-0.340 %/°C), so a warmer roof scales both curves by the same factor: the totals fall together and neither panel gains on the other. - **Cumulative output, STP670S-D66/Wmh:** 21,714 kWh - **Cumulative output, STP660S-D66/Pmh+:** 21,734 kWh - **Gap:** 20 kWh ## Output when hot | Condition | Cell temperature | STP670S-D66/Wmh | STP660S-D66/Pmh+ | Retained | | --- | --- | --- | --- | --- | | Standard test conditions | 25 °C | 670 W | 660 W | 100.0% of rated power | | Cool, bright day | 40 °C | 636 W | 626 W | 94.9% of rated power | | Typical summer roof | 55 °C | 602 W | 593 W | 89.8% of rated power | | Hot roof | 70 °C | 567 W | 559 W | 84.7% of rated power | ## Against the whole database | Measure | STP670S-D66/Wmh | STP660S-D66/Pmh+ | Out of | Note | | --- | --- | --- | --- | --- | | Efficiency | #7,652 | #9,076 | 14,005 | STP670S-D66/Wmh leads by 1,424 places | | Power density | #7,644 | #8,959 | 14,005 | STP670S-D66/Wmh leads by 1,315 places | | Heat behaviour | #8,778 | #8,778 | 14,005 | Tied - the same position in the database | | Weight | #3,317 | #10,874 | 14,005 | STP670S-D66/Wmh leads by 7,557 places | | Warranty | #9,798 | #21 | 14,005 | STP660S-D66/Pmh+ leads by 9,777 places | | Overall | #3,364 | #2,610 | 14,005 | STP660S-D66/Pmh+ leads by 754 places | ## Questions ### Which panel is better: Suntech STP670S-D66/Wmh or Suntech STP660S-D66/Pmh+? According to our database: **Suntech STP670S-D66/Wmh** has higher module efficiency (**21.60%** vs **21.20%**). See the full spec comparison and 30-year energy simulation above for a complete picture. ### What is the efficiency of Suntech STP670S-D66/Wmh and Suntech STP660S-D66/Pmh+? **Suntech STP670S-D66/Wmh** has a module efficiency of **21.60%**, while **Suntech STP660S-D66/Pmh+** is **21.20%**. Higher efficiency means more electricity from the same roof area - useful when space is limited. ### What cell technology does Suntech STP670S-D66/Wmh use vs Suntech STP660S-D66/Pmh+? **Suntech STP670S-D66/Wmh** uses **TOPCon** cells; **Suntech STP660S-D66/Pmh+** uses **TOPCon**. Modern **n-type** technologies (**TOPCon**, **HJT**, BC) typically deliver higher efficiency and lower degradation compared to older **PERC** (p-type) cells. ### What is the warranty on Suntech STP670S-D66/Wmh and Suntech STP660S-D66/Pmh+? **Suntech STP670S-D66/Wmh** has a **25 years** power warranty; **Suntech STP660S-D66/Pmh+** has a **30 years** power warranty. The power warranty guarantees a minimum percentage of rated output at the end of the warranty period (typically 80**-87%**). Product (materials) warranties are usually shorter. ### Are Suntech STP670S-D66/Wmh and Suntech STP660S-D66/Pmh+ bifacial panels? **Suntech STP660S-D66/Pmh+** is bifacial (captures light from both faces); **Suntech STP670S-D66/Wmh** is monofacial. Bifacial panels work best on ground mounts or raised structures with a light-coloured surface underneath. ## Related comparisons - [Suntech STP670S-D66/Wmh vs Suntech STP700S-D66-Nsh+](https://comparepv.com/compare/suntech-stp670s-d66-wmh/suntech-stp700s-d66-nsh) - 12 differences, the largest is module efficiency - [Suntech STP670S-D66/Wmh vs Suntech STP675S-D66/Wmh](https://comparepv.com/compare/suntech-stp670s-d66-wmh/suntech-stp675s-d66-wmh) - The same specification on paper - [Suntech STP670S-D66/Wmh vs Suntech STP670S-D66/Pmh+](https://comparepv.com/compare/suntech-stp670s-d66-wmh/wuxi-suntech-power-co-ltd-stp670s-d66-pmh) - 6 differences, the largest is performance warranty - [Suntech STP670S-D66/Wmh vs Suntech STP665S-D66/Wmh](https://comparepv.com/compare/suntech-stp670s-d66-wmh/suntech-stp665s-d66-wmh) - One difference: module efficiency - [Suntech STP670S-D66/Wmh vs Suntech STP665S-D66/Pmh+](https://comparepv.com/compare/suntech-stp670s-d66-wmh/wuxi-suntech-power-co-ltd-stp665s-d66-pmh) - 7 differences, the largest is performance warranty - [Suntech STP670S-D66/Wmh vs Suntech STP660S-D66/Wmh](https://comparepv.com/compare/suntech-stp670s-d66-wmh/suntech-stp660s-d66-wmh) - 3 differences, the largest is module efficiency --- Source: https://comparepv.com/compare/suntech-stp670s-d66-wmh/wuxi-suntech-power-co-ltd-stp660s-d66-pmh Not in this file, on the page: the thirty-year yield curve year by year at a cell temperature you pick and a written summary generated on request.