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640 vs 655 16 of 19 identical Swap Change panels

Suntech STP-NT11/66QGDF-640 vs Suntech STP-NT11/66QGDF-655

Suntech STP-NT11/66QGDF-640
STP-NT11/66QGDF-640
640 Wp 23.70 % TOPCon Bifacial
Open panel page Datasheet PDF
VS
Suntech STP-NT11/66QGDF-655
STP-NT11/66QGDF-655
655 Wp 24.20 % TOPCon Bifacial
Open panel page Datasheet PDF
The verdict

655 leads on the differences that matter

The largest is module efficiency: 0.50 pp more efficient. 16 of 19 comparable parameters are identical.

See all 3 differences
How alike are they
16 of 19 comparable
parameters are identical
identical differs
01

What actually differs

3 of 19 parameters
Parameter 640 655 Difference
Module efficiency 23.70 % 24.20 % 0.50 pp more efficient
Power density 236.9 Wp/m² 242.5 Wp/m² 5.6 Wp/m² higher
Rated power 640 Wp 655 Wp 15 W more power
02

What it means on a roof

Thirty years of production
Each panel's own declared degradation curve, at 1,200 kWh/kWp a year
Same temp coeff. for both panels (-0.260 %/°C), so a warmer roof scales both curves by the same factor: the totals fall together and neither panel gains on the other.
640
21,640 kWh
655
22,148 kWh
Lifetime gap
508 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 640 655
Standard test conditions 25 °C 100.0% of rated power 640 W 655 W
Cool, bright day 40 °C 96.1% of rated power 615 W 629 W
Typical summer roof 55 °C 92.2% of rated power 590 W 604 W
Hot roof 70 °C 88.3% of rated power 565 W 578 W
03

Full specification

Parameter 640 655 Difference
Power and efficiency
Rated power 640 Wp 655 Wp +15 W for 655
Module efficiency 23.70 % 24.20 % +0.50 pp for 655
Power density 236.9 Wp/m² 242.5 Wp/m² +5.6 Wp/m² for 655
Open-circuit voltage 49.70 V 50.15 V Effectively the same
Voltage at max power 41.47 V 41.91 V Effectively the same
Short-circuit current 16.22 A 16.43 A Effectively the same
Current at max power 15.43 A 15.63 A Effectively the same
Temperature
Temperature coefficient -0.260 %/°C -0.260 %/°C Same
Mechanical
Dimensions 2382x1134x30 mm 2382x1134x30 mm Same
Module area 2.701 m² 2.701 m² Same
Weight 33.1 kg 33.1 kg Same
Weight per kWp 51.7 kg/kWp 50.5 kg/kWp Effectively the same
Warranty and degradation
Product warranty 15 yrs 15 yrs Same
Performance warranty 30 yrs 30 yrs Same
Annual degradation 0.35 %/yr 0.35 %/yr Same
Technology
Cell technology TOPCon TOPCon Same
Cell type Monocrystalline Monocrystalline Same
Cell count 264 264 Same
Bifacial Yes Yes Same
04

Against the whole database

14,005 panels
Efficiency
#517 vs #184
655 leads by 333 places
Power density
#521 vs #172
655 leads by 349 places
Heat behaviour
#511 vs #511
Tied - the same position in the database
Weight
#5,083 vs #3,911
655 leads by 1,172 places
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#1,271 vs #747
655 leads by 524 places
05

More useful comparisons

Open the full database
Same series, other bin
Suntech STP-NT11/66QGDF-640 vs Suntech STP730S-D66-Nsh+
10 differences, the largest is rated power
Same series, other bin
Suntech STP-NT11/66QGDF-640 vs Suntech STP-NT11/66QGDF-670
4 differences, the largest is module efficiency
Same series, other bin
Suntech STP-NT11/66QGDF-640 vs Suntech STP-NT11/66QGDF-665
3 differences, the largest is module efficiency
Same series, other bin
Suntech STP-NT11/66QGDF-640 vs Suntech STP-NT11/66QGDF-660
3 differences, the largest is module efficiency
Same series, other bin
Suntech STP-NT11/66QGDF-640 vs Suntech STP-NT11/66QGDF-650
3 differences, the largest is module efficiency
Same series, other bin
Suntech STP-NT11/66QGDF-640 vs Suntech STP-NT11/66QGDF-645
One difference: module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Suntech STP-NT11/66QGDF-640 or Suntech STP-NT11/66QGDF-655?
According to our database: Suntech STP-NT11/66QGDF-655 has higher module efficiency (24.20% vs 23.70%). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of Suntech STP-NT11/66QGDF-640 and Suntech STP-NT11/66QGDF-655?
Suntech STP-NT11/66QGDF-640 has a module efficiency of 23.70%, while Suntech STP-NT11/66QGDF-655 is 24.20%. Higher efficiency means more electricity from the same roof area - useful when space is limited.
What cell technology does Suntech STP-NT11/66QGDF-640 use vs Suntech STP-NT11/66QGDF-655?
Suntech STP-NT11/66QGDF-640 uses TOPCon cells; Suntech STP-NT11/66QGDF-655 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 STP-NT11/66QGDF-640 and Suntech STP-NT11/66QGDF-655?
Suntech STP-NT11/66QGDF-640 has a 30 years power warranty; Suntech STP-NT11/66QGDF-655 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 STP-NT11/66QGDF-640 and Suntech STP-NT11/66QGDF-655 bifacial panels?
Both Suntech STP-NT11/66QGDF-640 and Suntech STP-NT11/66QGDF-655 are bifacial - they capture reflected light from the ground, which can add 5-15% more annual energy on ground-mount or elevated rooftop installations with a light surface beneath.

Shop prices: See 31 Suntech offers

Every figure here is from the manufacturers' own datasheets - a dash means the value is not published, never an estimate. The thirty-year projection and the temperature scenarios are calculations from those figures, and each states its assumption above.