--- title: "Longi Solar LR7-54HJD-510M vs Longi Solar LR8-66HVD-645M - Solar Panel Comparison | ComparePV" description: "Compare Longi Solar LR7-54HJD-510M vs Longi Solar LR8-66HVD-645M side by side: what actually differs, output when it is hot, thirty-year production, and the full specification." source: "https://comparepv.com/compare/longi-lr7-54hjd-510m/longi-lr8-66hvd-645m" updated: 2026-09-11 --- # Longi Solar LR7-54HJD-510M vs Longi Solar LR8-66HVD-645M LR7-54HJD-510M leads on the differences that matter The largest is module efficiency: 1.12 pp more efficient. 5 of 19 comparable parameters are identical. ## The two panels | Attribute | A | B | | --- | --- | --- | | Panel | [Longi Solar LR7-54HJD-510M](https://comparepv.com/panel/longi-lr7-54hjd-510m) | [Longi Solar LR8-66HVD-645M](https://comparepv.com/panel/longi-lr8-66hvd-645m) | | Manufacturer | Longi Solar | Longi Solar | | Power | 510 Wp | 645 Wp | | Efficiency | 25.00 % | 23.88 % | | Technology | Back Contact | Back Contact | ## Where they differ Ranked by how much the difference matters, not by datasheet order. | Parameter | LR7-54HJD-510M | LR8-66HVD-645M | Difference | | --- | --- | --- | --- | | Module efficiency | 25.00 % | 23.88 % | +1.12 pp for LR7-54HJD-510M | | Rated power | 510 Wp | 645 Wp | +135 W for LR8-66HVD-645M | | Power density | 249.9 Wp/m² | 238.8 Wp/m² | +11.1 Wp/m² for LR7-54HJD-510M | | Weight | 23.5 kg | 33.5 kg | -10.0 kg for LR7-54HJD-510M | | Product warranty | 30 yrs | 15 yrs | +15 yrs for LR7-54HJD-510M | | Temperature coefficient | -0.240 %/°C | -0.260 %/°C | +0.020 %/°C for LR7-54HJD-510M | | Weight per kWp | 46.1 kg/kWp | 51.9 kg/kWp | -5.9 kg/kWp for LR7-54HJD-510M | | Open-circuit voltage | 41.55 V | 49.62 V | 8.07 V apart | | Module area | 2.041 m² | 2.701 m² | 0.660 m² apart | | Voltage at max power | 34.37 V | 40.88 V | 6.51 V apart | | Cell count | 108 | 132 | 24 cells apart | | Short-circuit current | 15.52 A | 16.46 A | 0.94 A apart | | Dimensions | 1800x1134x30 mm | 2382x1134x30 mm | 1800x1134x30 mm vs 2382x1134x30 mm | | Current at max power | 14.84 A | 15.78 A | 0.94 A apart | ## Every compared parameter | Parameter | LR7-54HJD-510M | LR8-66HVD-645M | | --- | --- | --- | | Rated power | 510 Wp | 645 Wp | | Module efficiency | 25.00 % | 23.88 % | | Power density | 249.9 Wp/m² | 238.8 Wp/m² | | Open-circuit voltage | 41.55 V | 49.62 V | | Voltage at max power | 34.37 V | 40.88 V | | Short-circuit current | 15.52 A | 16.46 A | | Current at max power | 14.84 A | 15.78 A | | Temperature coefficient | -0.240 %/°C | -0.260 %/°C | | Dimensions | 1800x1134x30 mm | 2382x1134x30 mm | | Module area | 2.041 m² | 2.701 m² | | Weight | 23.5 kg | 33.5 kg | | Weight per kWp | 46.1 kg/kWp | 51.9 kg/kWp | | Product warranty | 30 yrs | 15 yrs | | Performance warranty | 30 yrs | 30 yrs | | Annual degradation | 0.35 %/yr | 0.35 %/yr | | Cell technology | Back Contact | Back Contact | | Cell type | Monocrystalline | Monocrystalline | | Cell count | 108 | 132 | | Bifacial | Yes | Yes | ## Thirty-year yield Each panel's own declared degradation curve, at 1,200 kWh/kWp a year - **Cumulative output, LR7-54HJD-510M:** 17,245 kWh - **Cumulative output, LR8-66HVD-645M:** 21,809 kWh - **Gap:** 4,564 kWh ## Output when hot | Condition | Cell temperature | LR7-54HJD-510M | LR8-66HVD-645M | Retained | | --- | --- | --- | --- | --- | | Standard test conditions | 25 °C | 510 W | 645 W | 100.0% of rated power | | Cool, bright day | 40 °C | 492 W | 620 W | 96.1% of rated power | | Typical summer roof | 55 °C | 473 W | 595 W | 92.2% of rated power | | Hot roof | 70 °C | 455 W | 570 W | 88.3% of rated power | ## Against the whole database | Measure | LR7-54HJD-510M | LR8-66HVD-645M | Out of | Note | | --- | --- | --- | --- | --- | | Efficiency | #4 | #394 | 14,005 | LR7-54HJD-510M leads by 390 places | | Power density | #7 | #356 | 14,005 | LR7-54HJD-510M leads by 349 places | | Heat behaviour | #13 | #511 | 14,005 | LR7-54HJD-510M leads by 498 places | | Weight | #979 | #5,361 | 14,005 | LR7-54HJD-510M leads by 4,382 places | | Warranty | #21 | #21 | 14,005 | Tied - the same position in the database | | Overall | #1,144 | #1,084 | 14,005 | LR8-66HVD-645M leads by 60 places | ## Questions ### Which panel is better: Longi Solar LR7-54HJD-510M or Longi Solar LR8-66HVD-645M? According to our database: **Longi Solar LR7-54HJD-510M** has higher module efficiency (**25.00%** vs **23.88%**); **Longi Solar LR7-54HJD-510M** tolerates heat better (temp coeff **-0.240%/°C** vs **-0.260%/°C**). See the full spec comparison and 30-year energy simulation above for a complete picture. ### What is the efficiency of Longi Solar LR7-54HJD-510M and Longi Solar LR8-66HVD-645M? **Longi Solar LR7-54HJD-510M** has a module efficiency of **25.00%**, while **Longi Solar LR8-66HVD-645M** is **23.88%**. Higher efficiency means more electricity from the same roof area - useful when space is limited. ### What cell technology does Longi Solar LR7-54HJD-510M use vs Longi Solar LR8-66HVD-645M? **Longi Solar LR7-54HJD-510M** uses **Back Contact** cells; **Longi Solar LR8-66HVD-645M** uses **Back Contact**. 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 Longi Solar LR7-54HJD-510M and Longi Solar LR8-66HVD-645M? **Longi Solar LR7-54HJD-510M** has a **30 years** power warranty; **Longi Solar LR8-66HVD-645M** 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 Longi Solar LR7-54HJD-510M and Longi Solar LR8-66HVD-645M bifacial panels? Both **Longi Solar LR7-54HJD-510M** and **Longi Solar LR8-66HVD-645M** 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 - [Longi Solar LR7-54HJD-510M vs Longi Solar LR7-54HJD-505M](https://comparepv.com/compare/longi-lr7-54hjd-510m/longi-lr7-54hjd-505m) - One difference: module efficiency - [Longi Solar LR7-54HJD-510M vs Longi Solar LR7-54HJD-500M](https://comparepv.com/compare/longi-lr7-54hjd-510m/longi-lr7-54hjd-500m) - 3 differences, the largest is module efficiency - [Longi Solar LR7-54HJD-510M vs Longi Solar LR7-54HJD-495M](https://comparepv.com/compare/longi-lr7-54hjd-510m/longi-lr7-54hjd-495m) - 3 differences, the largest is module efficiency - [Longi Solar LR8-66HVD-645M vs Longi Solar LR8-66HVD-665M](https://comparepv.com/compare/longi-lr8-66hvd-645m/longi-lr8-66hvd-665m) - 3 differences, the largest is module efficiency - [Longi Solar LR8-66HVD-645M vs Longi Solar LR8-66HVD-660M](https://comparepv.com/compare/longi-lr8-66hvd-645m/longi-lr8-66hvd-660m) - 3 differences, the largest is module efficiency - [Longi Solar LR8-66HVD-645M vs Longi Solar LR8-66HVD-655M](https://comparepv.com/compare/longi-lr8-66hvd-645m/longi-lr8-66hvd-655m) - 3 differences, the largest is module efficiency --- Source: https://comparepv.com/compare/longi-lr7-54hjd-510m/longi-lr8-66hvd-645m 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.