Efficiency leader, no clear weak spot
The Just Solar JST-EFMH-(415-435)W-TD series is designed to maximize energy yield on a limited roof area - without the need to switch to oversized module formats. The use of N-type cells in TOPCon technology results in more stable operation over time and better utilization of radiation in challenging conditions, such as cloudy weather or early mornings and late afternoons during the autumn and winter seasons. A key advantage is the high resistance to degradation, which ensures that the installation remains profitable for a longer period, benefiting both private investors and companies seeking a return on investment.
The design, which divides the cells into halves, supports lower internal losses and improves the module's performance in partially shaded conditions, while refined electrical connections enhance performance in low light. This makes it a good choice for single-family homes, small commercial installations, and projects where a long product warranty and predictable energy production over the years are important.
Ranking
Signals from the data
Residential, commercial and shaded-installations.
Top 17% of the TOPCon 400-450 W segment, against a median of 22.00%.
Top 17% of the TOPCon 400-450 W segment, against a median of 220.2.
Maximum module efficiency reaches 22.3%, marginally outperforming direct peer comparables: Luxen Solar LUXPOWER N5 (22.28%), ZNShine ZXM7-UHLDD108 (22.28%), and Solitek SOLID Blackstar (22.27%). This translates to higher energy yield per constrained roof area without requiring additional modules.
N-type TOPCon cells exhibit zero susceptibility to Light-Induced Degradation (LID) and a typical temperature coefficient of approximately -0.30%/°C, versus -0.40%/°C for older PERC technology. This results in materially higher annual yield in warmer climates and better-preserved nameplate power throughout the system's lifetime.
The half-cut cell architecture (108 cells) halves the current per cell, reducing I²R resistive losses. The module's electrical layout means partial shading on the lower half less frequently suppresses the upper bypass zone — a meaningful advantage on rooftops with chimneys or eaves.
The manufacturer offers a 30-year linear power warranty — a longer horizon than the 25-year standard common among mid-tier suppliers. With first-year degradation ≤2% and ≤0.4%/year thereafter, the module should retain approximately 87% of STC nameplate power at year 30, supporting favorable long-term LCOE projections.
The JST-EFMH-(415-435)W-TD series was launched in 2023 and discontinued in 2024. This eliminates supply continuity for system expansions, limits availability of matching modules for any future replacements, and raises concern about long-term warranty fulfillment over the 30-year power guarantee horizon.
Just Solar does not appear on Bloomberg New Energy Finance (BNEF)'s bankable module manufacturer list. In practice, this complicates non-recourse project finance for commercial installations and may be a barrier when insurers or lenders require a certified Tier-1 module supplier as a condition of funding.
The manufacturer provides only a 12-year product (materials and workmanship) warranty, significantly below the mid-premium TOPCon market standard of 15–25 years (e.g., JA Solar and Jinko Solar at 15 years; Q CELLS at 25 years). The shorter coverage period increases the financial risk of out-of-warranty material defect costs, particularly relevant given the series is already discontinued.
- Efficiency of 22.3% matches the TOPCon 400-450W median
- Power density of 222.8 W/m² matches the TOPCon 400-450W median
- At -0.30%/°C, hot weather performance is typical for TOPCon 400-450W panels
- #5100 for efficiency, #6093 for temperature performance out of 14005 panels
Specifications
Datasheet charts
Measured curves published by Just Solar in this model's datasheet. A chart carrying a wattage was measured on that variant alone - only the ones that describe 435 Wp appear here. The rest cover the whole series.
Simulations
Degradation from this panel's own datasheet figures. No inverter, soiling or shading losses.
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