--- title: "Tongwei TWMND-78HD640 640W Solar Panel - Specs & Review | ComparePV" description: "Tongwei TWMND-78HD640 640W solar panel: 4 shop offers from 317.79 zł. Specs: 22.90% efficiency, Monocrystalline cells." source: "https://comparepv.com/panel/tongwei-twmnd-78hd640" updated: 2026-10-08 --- # Tongwei TWMND-78HD640 Strong in heat, no clear weak spot 1,086 panels in the segment TOPCon 600-650 W ## Identity - **Manufacturer:** Tongwei - **Model:** TWMND-78HD640 - **Series:** TWMND - **Rated power:** 640 W - **Cell technology:** TOPCon - **Bifacial:** yes ## Price offers Prices are the figure each shop printed, on that shop's side of VAT. | Shop | Market | Price | Per kWp | Availability | Last read | | --- | --- | --- | --- | --- | --- | | [Panele-Sloneczne.com](https://comparepv.com/go/928) | Poland | 317.79 zł net | 496.55 zł/kWp | In stock | Last read 8 Oct 01:09 | | [PVhurt](https://comparepv.com/go/87374) | Poland | 406.15 zł incl. VAT | 634.61 zł/kWp | In stock | Last read 8 Oct 01:41 | | [Sklep Soltech](https://comparepv.com/go/5020) | Poland | 332.64 zł net | 519.75 zł/kWp | Not stated | Last read 8 Oct 03:34 | | [AZ Solar Shop](https://comparepv.com/go/538657) | Italy | | | Not stated | Last read 8 Oct 02:14 | ## How it compares Compared against segment TOPCon 600-650 W (1086 panels). | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Power (Wp) | 640 W | 620 W | Strong - top 9% | | | Module efficiency | 22.90% | 22.80% | Typical | 2,359 | | Power density | 229.0 | 227.7 | Typical | 2,389 | | Temperature coefficient | -0.280 | -0.290 | Strong - top 7% | 1,309 | | Weight (kg) | 33.8 kg | 32.7 kg | Typical | | | Performance warranty | 30 yrs | 30 yrs | Typical | 21 | ### Full peer table | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Module efficiency | 22.90% | 22.80% | Typical | 2,359 | | Power density | 229.0 | 227.7 | Typical | 2,389 | | Temperature coefficient | -0.280 | -0.290 | Strong - top 7% | 1,309 | | Weight per kWp | 52.8 | 53.1 | Typical | 6,496 | | Performance warranty | 30 yrs | 30 yrs | Typical | 21 | ### Strengths - **-0.280 %/°C temperature coefficient** - Top 7% of the TOPCon 600-650 W segment, against a median of -0.290. Ranked 1,309th in the whole database. - **Best for:** Residential, commercial and hot-climate. ## Specification ### Electrical - **Rated power (Pmax):** 640 W - **Efficiency:** 22.90 % - **Voltage at Pmax (Vmp):** 48.22 V - **Current at Pmax (Imp):** 13.28 A - **Open-circuit voltage (Voc):** 57.40 V - **Short-circuit current (Isc):** 13.86 A - **Max system voltage:** 1500 V ### Temperature - **Temperature coefficient of Pmax:** -0.280 %/degC - **Temperature coefficient of Voc:** -0.240 %/degC - **Temperature coefficient of Isc:** 0.046 %/degC - **NOCT:** 45 degC ### Cell and construction - **Cell type:** Monocrystalline - **Cell technology:** TOPCon - **Cell count:** 156 - **Bifacial:** yes - **Bifacial gain:** 25.00 ### Physical - **Length:** 2465 mm - **Width:** 1134 mm - **Thickness:** 30 mm - **Weight:** 33.8 kg - **Area:** 2.80 m2 - **Power density:** 229.0 Wp/m2 ### Warranty and degradation - **Product warranty:** 12 years - **Performance warranty:** 30 years - **Output guaranteed at end of warranty:** 87.4 % - **First-year degradation:** 1.00 % - **Annual degradation:** 0.40 % - **Output after 30 years:** 559 W ## Rank in the whole catalogue | Measure | Position | | --- | --- | | Efficiency | 2359 of 14005 | | Power density | 2389 of 14005 | | Temperature coefficient | 1309 of 14005 | | Weight | 6496 of 14005 | | Warranty | 21 of 14005 | ## About this series The Tongwei TWMND series is an advanced solution based on **N-type TOPCon cell technology**, which sets new standards for efficiency in difficult lighting conditions. Thanks to the use of this innovative cell type, the modules are characterized by almost zero initial degradation effect and a significantly lower annual power drop, guaranteeing energy stability for investors for decades. A key feature of the series is its **excellent temperature coefficient**, allowing for high yields even during summer heat when traditional panels lose efficiency. The design utilizing a **multi-busbar (MBB)** system shortens the electron flow path and reduces the risk of micro-cracks, which directly increases the mechanical reliability of the product. The TWMND series is designed for demanding residential users and commercial projects where maximizing profit from the available roof or ground area matters. What sets these panels above the competition is **full control over silicon purity**, resulting from the manufacturer's position as a leader in raw material production, which translates into **exceptional durability and consistency of parameters** for every module. It is an uncompromising choice for those looking for modern technology that realistically shortens the return on investment in photovoltaics. ## Notable figures - Efficiency of 22.9% matches the \*\*TOPCon 600-650W\*\* median - At 228.9 W/m² power density, roof space requirements are typical for \*\*TOPCon 600-650W\*\* panels - At -0.28%/°C, hot weather performance is typical for \*\*TOPCon 600-650W\*\* panels - At 33.8 kg (1.1 kg above \*\*TOPCon 600-650W\*\* median of 32.7 kg), requires checking roof load capacity - Bifacial design (80% factor) captures reflected light - adds 4-12% yield on ground-mount or white roof ## Questions ### How does the N-type TOPCon technology in Tongwei TWMND panels differ from older P-type PERC cells? The N-type TOPCon cells used in the TWMND series deliver higher base efficiency and near-zero initial light-induced degradation (LID), which noticeably reduces power output in P-type PERC panels within the first days of operation. TOPCon also has a lower annual degradation rate, which, combined with the 30-year power warranty, translates into higher total energy yield over the system's lifetime compared to older technologies. ### What warranty comes with Tongwei TWMND panels and what does it cover? The TWMND series comes with a 12-year product warranty covering material and manufacturing defects, plus a 30-year linear power warranty guaranteeing a minimum percentage of rated output over time. These are among the longer warranty periods available on the market, making the series an attractive investment for both residential and commercial projects. ### What is multi-busbar (MBB) technology in Tongwei TWMND panels and why does it matter? Multi-busbar (MBB) technology uses a larger number of thin conductive paths on the cell surface instead of a few wide soldered ribbons. This shortens the electron flow path, reduces resistive losses, and significantly lowers the risk of micro-cracks during transport, installation, and operation. In practice, this results in higher mechanical reliability of the TWMND modules and more stable long-term energy output. ### Do Tongwei TWMND panels lose performance in hot weather? The TWMND series has a favorable temperature coefficient of power, typical of N-type TOPCon technology, meaning performance drop at high module operating temperatures is smaller than with panels based on older P-type cells. In practice, this results in higher energy yields on hot summer days, when traditional PERC panels start losing significant efficiency once module temperature exceeds 25°C. ### Are Tongwei TWMND panels bifacial? No, panels in this TWMND configuration are monofacial modules — they generate power only from the front side. This is well suited to installations where mounting on bifacial racking with reflected ground light isn't practical, such as sloped roofs. Customers looking for extra yield from reflected light should check other bifacial series in Tongwei's lineup. ### How many Tongwei TWMND 645 Wp panels are needed for a roughly 5 kWp system? With a maximum module output of 645 Wp, 8 panels are enough for a system of around 5 kWp (8 x 645 W ≈ 5.16 kWp). The high per-module power lets you reach a larger system size with fewer modules, reducing installation costs, the number of optimizers or microinverters needed, and the roof area required. ## Datasheet [Manufacturer datasheet (PDF)](https://comparepv.com/datasheets/TWMND-78HD-625645W30F-bbe7467e833d.pdf) ## Alternatives | Panel | Power | How it differs | | --- | --- | --- | | [AIKO AIKO-A650-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a650-mae72mw) | 650 W | Cooler, lighter, +2.3 pp | | [AIKO AIKO-A680-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a680-mde72mw) | 680 W | +40 W, lighter, +2.3 pp | | [AIKO AIKO-A675-MDE72Mw](https://comparepv.com/panel/aiko-aiko-a675-mde72mw) | 675 W | +35 W, lighter, +2.1 pp | | [AIKO AIKO-A645-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a645-mae72mw) | 645 W | Cooler, lighter, +2.1 pp | | [AIKO AIKO-G670-MCH72Mw](https://comparepv.com/panel/aiko-aiko-g670-mch72mw) | 670 W | +30 W, lighter, +1.9 pp | | [Longi Solar LR7-72HVHF-670M](https://comparepv.com/panel/longi-lr7-72hvhf-670m) | 670 W | +30 W, lighter, +1.9 pp | | [AIKO AIKO-A640-MAE72Mw](https://comparepv.com/panel/aiko-aiko-a640-mae72mw) | 640 W | Cooler, lighter, +1.9 pp | | [Tongwei TWMND-78HD625](https://comparepv.com/panel/tongwei-twmnd-78hd625) | 625 W | -15 W, -0.5 pp | | [Tongwei TWMND-78HD630](https://comparepv.com/panel/tongwei-twmnd-78hd630) | 630 W | -10 W, -0.4 pp | | [Tongwei TWMND-78HD635](https://comparepv.com/panel/tongwei-twmnd-78hd635) | 635 W | Very close match | | [Tongwei TWMND-78HD645](https://comparepv.com/panel/tongwei-twmnd-78hd645) | 645 W | +0.2 pp | | [AIKO AIKO-A700-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a700-mae78dw) | 700 W | +60 W, cooler, +2.1 pp | | [AIKO AIKO-A695-MAE78Dw](https://comparepv.com/panel/aiko-aiko-a695-mae78dw) | 695 W | +55 W, cooler, +2.0 pp | | [Jinko Solar JKM650-670N-66QL6-BDV (670W class)](https://comparepv.com/panel/jinko-solar-jkm650-670n-66ql6-bdv-670w-class) | 670 W | +30 W, cooler, +1.9 pp | --- Source: https://comparepv.com/panel/tongwei-twmnd-78hd640 Not in this file, on the page: the I-V and temperature curves lifted from the manufacturer's datasheet, a thirty-year output simulator, a bifacial gain calculator and alternatives filtered by how closely they match these dimensions.