Strong in heat, modest efficiency
The Hiwatt Solar HW-M6/120H(350-370) panel series is a modern solution based on Half-Cut cell technology, which significantly minimizes energy losses resulting from partial shading or module soiling. Thanks to the use of larger M6 silicon wafers and a Multi-Busbar system, these panels offer higher power density while maintaining optimal dimensions, making them an ideal choice for roofs with limited space. This design effectively reduces mechanical stress and the risk of micro-cracks, which directly translates into exceptional mechanical durability and long-term yield stability. They solve the problem of efficiency drops at high temperatures thanks to a favorable temperature coefficient, which sets them apart from standard modules available on the market. This series is dedicated to both individual prosumers and commercial projects looking for the optimal balance between price and innovation. The use of an anti-reflective coating allows for better light absorption even at a low angle of incidence of sunlight. Compared to the competition, the HW-M6/120H is characterized by a very low level of initial LID degradation, providing users with the certainty that their investment in photovoltaics will maintain high efficiency for decades, regardless of the harsh weather conditions typical of the Polish climate.
Ranking
Signals from the data
Residential, commercial and shaded-installations.
Tight roof space and roofs where every square metre has to count.
Top 15% of the PERC 350-400 W segment, against a median of -0.350.
Bottom 12% of the PERC 350-400 W segment, against a median of 19.90%.
Bottom 21% of the PERC 350-400 W segment, against a median of 199.0.
Half-cut cell architecture on M6 (166 mm) wafers combined with a Multi-Busbar layout reduces series resistance and partial-shading losses by up to 30% compared to conventional full-cell modules. This translates into higher annual energy yield on typical Polish rooftops with shading obstacles such as chimneys and dormers.
Peak module efficiency of 20.0% places the series above the peer-comparable Solitek SOLID Bifacial (19.57%) and nearly on par with Solarwatt Panel vision GM 3.0 style (19.9%) at the same 370 Wp power level. On a 20 m² roof, this gain over a previous-generation PERC module (≈18.5%) amounts to roughly 30 Wp extra with no change in module count.
The manufacturer provides a 25-year linear power output warranty, confirmed in the ENF Solar database for this series. At a typical PERC half-cut annual degradation rate of ≈0.55%/year, the module retains approximately 86.7% of nominal power after 25 years — an acceptable threshold for residential LCOE calculations.
PERC half-cut technology on M6 wafers exhibits lower Light Induced Degradation (LID) than older Al-BSF full-cell modules, typically below 1% in the first 1,000 operating hours. The tempered-glass anti-reflective coating improves light absorption at incidence angles above 60°, which is particularly relevant during the low-sun autumn and winter months in Poland.
The series covers five power steps across a 20 Wp range, making it straightforward to optimize module count against inverter MPPT window voltage limits without mixing different series in a single string.
The discontinued flag in the manufacturer's database means active production of the HW-M6/120H has ceased. Replacing a mechanically damaged module in an existing system may be impossible without redesigning the string, because matching frame color, Wp rating, and electrical parameters to legacy units is no longer guaranteed. This is especially problematic for systems above 10 kWp, where replacing only a subset of modules alters the string IV curve.
Hiwatt Solar does not appear on BloombergNEF's bankable Tier-1 list (confirmed absent from Q2 2025 and Q4 2025 editions). For commercial and utility-scale projects above 50 kWp seeking bank financing or leasing, the absence of Tier-1 status leads to stricter due diligence requirements or outright financing refusals by some institutions.
The series is monofacial, while the direct peer Solitek SOLID Bifacial (370 Wp, 19.57% efficiency) offers rear-side generation of 5–25% depending on ground albedo. On ground-mount or white-membrane roof installations, this represents a meaningful loss of annual production at no additional material cost.
The 12-year workmanship warranty is half the length of Panasonic EVERVOLT Black Series (25 years) and a fraction of Solarwatt Panel vision GM 3.0 (30-year combined warranty). Over a standard 25-year system lifetime, the last 13 years fall outside product warranty coverage, shifting the financial risk of manufacturing defects — delamination, cell corrosion — entirely to the system owner.
Peak efficiency of 20.0% lags 1.2 percentage points behind the Panasonic EVERVOLT 370K (21.2%), which operates in the same nominal power class. On a constrained roof area of 30 m², this difference means that achieving 5.55 kWp requires 15 HW-M6/120H modules (at 370 Wp each), whereas 14 Panasonic units suffice — a relevant constraint for mansard roofs and garages.
- Module efficiency of 18.9% is 0.6pp below average for PERC 0-400W panels (median: 19.4%)
- Power density of 192.1 W/m² matches the PERC 0-400W median
- Temperature coefficient of -0.34%/°C matches the PERC 0-400W median
- In the top 93% for efficiency among all PERC panels
Specifications
Simulations
Degradation from this panel's own datasheet figures. No inverter, soiling or shading losses.
Alternatives
Found 210 panels of the same or similar size to this one, within ±10 mm. See them here Found 271 panels of the same or similar size to this one, within ±25 mm. See them here Found 332 panels of the same or similar size to this one, within ±50 mm. See them here Found 4151 panels of the same or similar size to this one, within ±100 mm. See them here