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TL;DR
The efficiency of a panel = % of the solar energy received converted into electricity. Current range: 20–23% for commercial TOPCon/HJT modules. The efficiency determines the roof area needed: the higher the efficiency, the less m² of roof you need.
Definition
The efficiency of a photovoltaic module is the ratio between the electrical power produced and the light power received by the surface of the module, expressed as a percentage. Measured in STC conditions (1 000 W/m², 25°C, AM 1.5).
TOPCon 2026
21.5–22.5%
HJT 2026
21.8–23.2%
PERC (old)
20–21%
Laboratory record
29.1% (perovskite)
Efficiency = Power (W) / (Irradiance (W/m²) × Surface (m²)). A 440 Wp module measuring 1.75 m² under 1 000 W/m² has an efficiency = 440 / (1 000 × 1.75) = 25.1% — laboratory value. In real conditions, the effective efficiency is reduced by temperature, variable irradiance and system losses: 18–21% in practice. Do not confuse module efficiency and PR (performance ratio) of the installation.
Evolution of commercial module yield in Switzerland: 2015: 17–18% (PERC), 2020: 19–20% (improved PERC), 2023: 21–22% (TOPCon), 2026: 21.5–23.2% (TOPCon/HJT). The gain in efficiency allows more power to be installed on the same roof surface.
Related guides
Yes slightly. The annual degradation of 0.35–0.45% for N-Type means that after 25 years, the efficiency is at 90–91% of its initial value — eg: a panel at 22% initial will be at ~20% after 25 years.
If roof area is limited, yes — each additional % efficiency = more watts on the same area. If the surface area is large, performance is secondary to value for money and durability.
Sources & method
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