Understanding modules

Modules all look alike but aren't. Four things are worth understanding — then you see through any "premium" promise.

Mono- vs bifacial modules

• Monofacial: glass front, polymer backsheet behind. Collects light from the front only.
• Bifacial (glass-glass): glass on both sides; the rear also collects reflected light.

The model number reveals the construction. Example, Aiko Neostar "A490-MCE54Dw": the Dw = Dual-glass = bifacial; Mw = mono-glass = monofacial. The same 490 W cell exists in both.

The rear-side gain is real but usually modest — and near zero when the roof faces away from afternoon light (both then run on diffuse light). Roof orientation dominates, not module construction.

Cell quality

Newer cell types (e.g. Aiko ABC at ~24.5% efficiency with good shade tolerance) extract more from the same area and cope better with partial shading. Higher efficiency means more kWp on a limited roof.

Product vs performance warranty — don't confuse them

Two different promises, often deliberately blurred:

• Product warranty: the module itself is free of material/workmanship defects — e.g. 25 years.
• Performance warranty: the module still delivers at least Y% of its output after X years — e.g. 30 years to a minimum remaining output.

An offer that just says "25-year warranty" often means only one of them. Demand both, in years.

Tier-1 doesn't mean "best quality"

"Tier-1" is a bankability ranking (Bloomberg) — it says how financeable a maker is, not directly how good the module is. But it correlates with whether the maker will still exist in 25 years to honour the warranty.

In short: read the construction from the model number (Dw/Mw), watch cell quality and separate product AND performance warranties, and treat Tier-1 as a survival badge, not a quality one.

On to the second big building block: battery storage.