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Fellow Energy Brand review

FE66-18X

500 Wp PERC Bifacial
ComparePV verdict

Light for its output, short guarantee

Rank 9,819 of 14,005
Compare panels Datasheet PDF
Power (Wp)
500
Weak · bottom 4%
Efficiency (%)
21.10
Strong · top 20%
Density (Wp/m²)
210.6
Typical · median 209.0
Temp (%/°C)
-0.350
Typical · median -0.350
Weight (kg)
25.0
Strong · 3.4 kg below median
Warranty (yrs)
25
Weak · bottom 23%

The Fellow Energy FE66-18X series consists of monocrystalline panels based on half-cut PERC technology, which effectively minimize energy losses caused by shading and light-induced degradation (LID). The use of half-cut cells reduces the module's internal resistance, resulting in improved energy yield even under challenging conditions - cloud cover or elevated temperatures. Thanks to the 10-busbar design, the cells operate more efficiently, and the risk of hot spot formation is significantly reduced. The panels are available in various aesthetic variants, including a Full Black version, making them an attractive choice for residential rooftop installations where aesthetics matter. Compatibility with a 1500 VDC system voltage allows for the design of longer strings and reduces installation costs on the BOS side. The FE66-18X series performs well both in prosumer installations and in commercial projects requiring proven modules with high power density. It is a solid choice for installers seeking a balance between build quality, durability, and price.

Ranking

706 panels in the segment PERC 500-550 W
Metric This panel Median Position in segment Overall rank
Module efficiency 21.10% 20.90% Strong · top 20% 9,297
Power density 210.6 209.0 Typical 9,583
Temperature coefficient -0.350 -0.350 Typical 10,419
Weight per kWp 50.0 53.0 Strong · top 16% 3,317
Performance warranty 25 yrs 30 yrs Weak · bottom 23% 9,798
Colour key Strong - top 25% Typical - middle 50% Weak - bottom 25%

Signals from the data

7 positive · 5 caution
Best for

Residential, commercial and shaded-installations.

Not ideal for

Owners who want a long output guarantee.

Strengths
50.0 kg per kWp

Top 16% of the PERC 500-550 W segment, against a median of 53.0.

21.10% module efficiency

Top 20% of the PERC 500-550 W segment, against a median of 20.90%.

Watch-outs
25 year performance warranty

Bottom 23% of the PERC 500-550 W segment, against a median of 30 yrs.

What owners get
Bifacial design with active rear side

The dual-glass bifacial construction captures albedo-reflected irradiance from the ground surface (light membrane, gravel, concrete), delivering an additional 5–15% energy yield compared to a monofacial module of the same nameplate power under typical mounting conditions.

10BB half-cut PERC – reduced hotspot risk

Ten busbars combined with half-cut cells reduce internal module resistance and limit mismatch losses under partial shading. The hotspot risk is significantly lower than in legacy 5–6 BB full-cell modules, contributing to longer laminate service life.

1500 VDC system voltage compatibility

Support for 1500 VDC systems allows strings of ~24–26 modules, reducing the number of MPPT inputs and overall BoS costs (cabling, connectors, protective devices) by approximately 5–10% compared to 1000 VDC designs.

21.1% efficiency – leading edge of the 500 Wp PERC segment

At 500 Wp and 21.1% efficiency, the module outperforms direct peers: Emmvee GRAPHITE Monoperc Black (21.03%) and Lina Energy LEPV 132 HC ICON PLUS (21.06%), delivering higher power density and requiring less roof area per installed kWp.

Full Black variant – residential aesthetics

The Full Black option (black frame, black backsheet) positions the series competitively in the residential rooftop segment, where uniform appearance influences purchasing decisions and can support a higher installation price point.

Trade-offs
Discontinued series – limited serviceability

The FE66-18X line is officially discontinued, meaning no new modules are available for system expansion, warranty replacement stock is constrained, and long-term service continuity is at risk. The manufacturer – Jiangsu Xiehang Energy Technology (founded 2020) – has a short market track record, further amplifying service continuity risk.

PERC technology – superseded by N-type TOPCon

By 2024, TOPCon exceeded 66% of global production capacity, displacing PERC (down to ~35–40% share). TOPCon modules deliver a temperature coefficient of approx. -0.29%/°C versus -0.35%/°C for the FE66-18X, translating to approximately 1.5–2.5% higher annual yield at the same nameplate power — a measurable LCOE disadvantage versus current-generation modules.

Power warranty at 83.1% after 25 years – below premium standard

The manufacturer guarantees ≥83.1% of rated power after 25 years, while leading Tier-1 brands (Jinko, LONGi, JA Solar) guarantee 84.8–87.4% over the same period. The 1.3–4.3 percentage-point gap translates into measurably lower cumulative energy yield over the module's full service life.

Significant efficiency gap vs. peer Gokin GK-3-54HGF

At the same 500 Wp nameplate, the Gokin GK-3-54HGF achieves 24.5% efficiency versus 21.1% for the FE66-18X — a 3.4 pp difference (~16% higher power density). For area-constrained residential rooftops, this directly caps the maximum installable system power.

Notes from the database
  • Efficiency of 21.1% matches the PERC 500-550W median
  • Power density of 210.6 W/m² matches the PERC 500-550W median
  • Temperature coefficient of -0.35%/°C matches the PERC 500-550W median
  • Weight of 25.0 kg (3.4 kg below PERC 500-550W median of 28.4 kg) allows easier transport and roof mounting
  • Ranked #9297 out of 14005 panels for efficiency in the database

Specifications

Open datasheet PDF
Nominal power (Pmax) 500 Wp Nameplate at 1000 W/m², 25 °C
Module efficiency 21.10 % Strong Segment median 20.90%
Vmpp · Impp 38.37 V · 13.04 A Operating point at max power
Voc · Isc 45.55 V · 13.93 A Sizes the string length
Max system voltage 1500 V Longer strings than 1000 V modules
Dimensions 2094×1134×35 mm · 2.37 m² of roof
Weight 25.0 kg Strong Strong · 3.4 kg below median
Cells 132 · PERC Monocrystalline
Coefficient Pmax -0.350 %/°C Typical median -0.350 of its segment
Coefficient Voc · Isc -0.275 · 0.045 %/°C
Product warranty 12 years Hardware defects only
Performance warranty 25 years Weak bottom 23% · median 30 yrs
End-of-warranty output 83.1 % Equals 401 W guaranteed
Degradation 2.50 → 0.60 % First year, then annual

Simulations

Live - change any input
Lifetime output & value
30 years at 1200 kWh/kWp/year and €0.50 per kWh
Power in year 30
-
Lifetime energy
-
Energy value
-

Degradation from this panel's own datasheet figures. No inverter, soiling or shading losses.

Heat losses
-0.350 %/°C against a segment median of -0.350
-
Filter these
Size
Panel Power Eff. Temp. Weight Difference
Fellow Energy FE66-18X 500 W 21.10% -0.350 25.0 kg You are here
LR7-54HJD-510M 510 W 25.00% -0.240 23.5 kg Cooler, +3.9 pp, +5 yr warranty
AIKO-A495-MCE54Mw 495 W 24.80% -0.260 21.0 kg Cooler, +3.7 pp, +5 yr warranty
LR7-54HJD-505M 505 W 24.70% -0.240 23.5 kg Cooler, +3.6 pp, +5 yr warranty
AIKO-A490-MCE54Mw 490 W 24.50% -0.260 21.0 kg Cooler, +3.4 pp, +5 yr warranty
LR7-54HJD-500M 500 W 24.50% -0.240 23.5 kg Cooler, +3.4 pp, +5 yr warranty
CIPRO-TN9C54M-500W 500 W 24.50% -0.260 21.4 kg Cooler, +3.4 pp, +5 yr warranty
GKA120N-PRO-590W 590 W 23.82% -0.300 26.7 kg +90 W, +2.7 pp, +5 yr warranty
GKA120N-PRO-585W 585 W 23.62% -0.300 26.7 kg +85 W, +2.5 pp, +5 yr warranty
BGO 580 580 W 23.50% -0.290 26.0 kg +80 W, cooler, +2.4 pp
GKA120N-PRO-580W 580 W 23.42% -0.300 26.7 kg +80 W, +2.3 pp, +5 yr warranty

Found 397 panels of the same or similar size to this one, within ±10 mm. See them here Found 408 panels of the same or similar size to this one, within ±25 mm. See them here Found 425 panels of the same or similar size to this one, within ±50 mm. See them here Found 953 panels of the same or similar size to this one, within ±100 mm. See them here

Common questions

6 answered
What warranty does the Fellow Energy FE66-18X series come with?
The FE66-18X series includes a 12-year product warranty covering manufacturing defects and materials, plus a 25-year linear power output warranty. After 25 years, the module is guaranteed to produce at least the stated minimum percentage of its rated power. Fellow Energy is a Tier 1 manufacturer, which adds credibility to these long-term warranty commitments.
Are the FE66-18X panels bifacial, and does that matter for a typical pitched roof installation?
Yes, the FE66-18X series features bifacial cells that generate power from both sides of the module. On a pitched roof with a light-colored underlayer or high-reflectance membrane, you can expect an additional yield of 5–15% compared to standard monofacial modules. The bifacial gain is greatest in ground-mounted systems with a white or highly reflective surface beneath the panels.
What is half-cut PERC technology and why does the FE66-18X series use it?
Half-cut PERC is a technology where solar cells are laser-cut in half, reducing internal resistance and limiting losses from partial shading caused by chimneys or antennas. The PERC passivation layer increases electron recovery and improves efficiency, especially under diffuse light. The FE66-18X also uses a 10-busbar design, which further reduces the risk of hot spots forming on the module.
Is the Fellow Energy FE66-18X available in a Full Black version, and is it suitable for residential rooftops?
Yes, the FE66-18X series is available in a Full Black variant with a black frame and black backsheet, making it an aesthetically pleasing choice for residential rooftop installations. It is ideal for homeowners who want a discreet, uniform look. With up to 500 Wp per module, the series delivers high power density, so fewer panels are needed to reach the target system output.
Can an FE66-18X installation operate at a 1500 V system voltage?
Yes, the Fellow Energy FE66-18X modules are rated for a 1500 VDC system voltage. This allows longer string configurations with more modules in series, reducing the number of DC cables and inverters needed and lowering overall BoS costs. This is especially beneficial in large commercial or industrial PV projects where minimizing balance-of-system expenses significantly impacts LCOE.
How do the FE66-18X panels perform in high temperatures or on overcast days?
The half-cut PERC technology in the FE66-18X series reduces internal resistance, which limits thermal losses at elevated cell temperatures. The cell design also minimizes light-induced degradation (LID). On overcast days, the modules make better use of diffuse irradiance compared to older monocrystalline technologies, resulting in higher annual energy yields in climates with frequent cloud cover.
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