--- title: "Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-DEG21C.20-660 - Solar Panel Comparison | ComparePV" description: "Compare Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-DEG21C.20-660 side by side: what actually differs, output when it is hot, thirty-year production, and the full specification." source: "https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-co-ltd-tsm-deg21c-20-660" updated: 2026-09-11 --- # Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-DEG21C.20-660 660 leads on the differences that matter The largest is module efficiency: 0.40 pp more efficient. 16 of 19 comparable parameters are identical. ## The two panels | Attribute | A | B | | --- | --- | --- | | Panel | [Trina Solar TSM-DEG21C.20-645](https://comparepv.com/panel/trina-solar-co-ltd-tsm-deg21c-20-645) | [Trina Solar TSM-DEG21C.20-660](https://comparepv.com/panel/trina-solar-co-ltd-tsm-deg21c-20-660) | | Manufacturer | Trina Solar | Trina Solar | | Power | 645 Wp | 660 Wp | | Efficiency | 20.80 % | 21.20 % | | Technology | PERC | PERC | ## Where they differ Ranked by how much the difference matters, not by datasheet order. | Parameter | 645 | 660 | Difference | | --- | --- | --- | --- | | Module efficiency | 20.80 % | 21.20 % | +0.40 pp for 660 | | Power density | 207.6 Wp/m² | 212.5 Wp/m² | +4.8 Wp/m² for 660 | | Rated power | 645 Wp | 660 Wp | +15 W for 660 | ## Every compared parameter | Parameter | 645 | 660 | | --- | --- | --- | | Rated power | 645 Wp | 660 Wp | | Module efficiency | 20.80 % | 21.20 % | | Power density | 207.6 Wp/m² | 212.5 Wp/m² | | Open-circuit voltage | 45.30 V | 45.90 V | | Voltage at max power | 37.50 V | 38.10 V | | Short-circuit current | 18.31 A | 18.45 A | | Current at max power | 17.23 A | 17.35 A | | Temperature coefficient | -0.340 %/°C | -0.340 %/°C | | Dimensions | 2384x1303x33 mm | 2384x1303x33 mm | | Module area | 3.106 m² | 3.106 m² | | Weight | 38.3 kg | 38.3 kg | | Weight per kWp | 59.4 kg/kWp | 58.0 kg/kWp | | Product warranty | 12 yrs | 12 yrs | | Performance warranty | 30 yrs | 30 yrs | | Annual degradation | 0.45 %/yr | 0.45 %/yr | | Cell technology | PERC | PERC | | Cell type | Monocrystalline | Monocrystalline | | Cell count | 132 | 132 | | Bifacial | Yes | 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, 645:** 21,240 kWh - **Cumulative output, 660:** 21,734 kWh - **Gap:** 494 kWh ## Output when hot | Condition | Cell temperature | 645 | 660 | Retained | | --- | --- | --- | --- | --- | | Standard test conditions | 25 °C | 645 W | 660 W | 100.0% of rated power | | Cool, bright day | 40 °C | 612 W | 626 W | 94.9% of rated power | | Typical summer roof | 55 °C | 579 W | 593 W | 89.8% of rated power | | Hot roof | 70 °C | 546 W | 559 W | 84.7% of rated power | ## Against the whole database | Measure | 645 | 660 | Out of | Note | | --- | --- | --- | --- | --- | | Efficiency | #10,457 | #9,076 | 14,005 | 660 leads by 1,381 places | | Power density | #10,562 | #8,959 | 14,005 | 660 leads by 1,603 places | | Heat behaviour | #8,778 | #8,778 | 14,005 | Tied - the same position in the database | | Weight | #12,126 | #11,529 | 14,005 | 660 leads by 597 places | | Warranty | #21 | #21 | 14,005 | Tied - the same position in the database | | Overall | #4,248 | #3,228 | 14,005 | 660 leads by 1,020 places | ## Questions ### Which panel is better: Trina Solar TSM-DEG21C.20-645 or Trina Solar TSM-DEG21C.20-660? According to our database: **Trina Solar TSM-DEG21C.20-660** has higher module efficiency (**21.20%** vs **20.80%**). See the full spec comparison and 30-year energy simulation above for a complete picture. ### What is the efficiency of Trina Solar TSM-DEG21C.20-645 and Trina Solar TSM-DEG21C.20-660? **Trina Solar TSM-DEG21C.20-645** has a module efficiency of **20.80%**, while **Trina Solar TSM-DEG21C.20-660** is **21.20%**. Higher efficiency means more electricity from the same roof area - useful when space is limited. ### What cell technology does Trina Solar TSM-DEG21C.20-645 use vs Trina Solar TSM-DEG21C.20-660? **Trina Solar TSM-DEG21C.20-645** uses **PERC** cells; **Trina Solar TSM-DEG21C.20-660** uses **PERC**. 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 Trina Solar TSM-DEG21C.20-645 and Trina Solar TSM-DEG21C.20-660? **Trina Solar TSM-DEG21C.20-645** has a **30 years** power warranty; **Trina Solar TSM-DEG21C.20-660** 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 Trina Solar TSM-DEG21C.20-645 and Trina Solar TSM-DEG21C.20-660 bifacial panels? Both **Trina Solar TSM-DEG21C.20-645** and **Trina Solar TSM-DEG21C.20-660** 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. ## Related comparisons - [Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-DEG21C.20-665](https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-co-ltd-tsm-deg21c-20-665) - 3 differences, the largest is module efficiency - [Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-DEG21C.20-655](https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-co-ltd-tsm-deg21c-20-655) - 3 differences, the largest is module efficiency - [Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-DEG21C.20-650](https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-co-ltd-tsm-deg21c-20-650) - The same specification on paper - [Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-NEG21C.20Q-760](https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-tsm-neg21c-20q-760) - 11 differences, the largest is module efficiency - [Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-NEG21C.20Q-755](https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-tsm-neg21c-20q-755) - 11 differences, the largest is module efficiency - [Trina Solar TSM-DEG21C.20-645 vs Trina Solar TSM-NEG21C.20Q-750](https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-tsm-neg21c-20q-750) - 10 differences, the largest is module efficiency --- Source: https://comparepv.com/compare/trina-solar-co-ltd-tsm-deg21c-20-645/trina-solar-co-ltd-tsm-deg21c-20-660 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.