European Inverter Efficiency

η_EU = weighted average of partial-load efficiencies

Calculator

Euro Efficiency

η at 5% load

η at 10% load

η at 20% load

η at 30% load

η at 50% load

η at 100% load

Result

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Formula

η_EU = 0.03×η₅ + 0.06×η₁₀ + 0.13×η₂₀ + 0.10×η₃₀ + 0.48×η₅₀ + 0.20×η₁₀₀

Description

The European efficiency is a weighted-average inverter efficiency that accounts for the fact that solar inverters rarely operate at full power. The weighting factors reflect the typical irradiance distribution in central European climates, where partial-load conditions dominate. The 50% load point receives the highest weight (48%) because inverters spend the most time near this operating point. This metric gives a more realistic picture of annual energy harvest than the peak efficiency, which only occurs at one specific operating point.

Variables

η_EU — Weighted European efficiency (0-1 or %)
η₅ through η₁₀₀ — Efficiency at 5%, 10%, 20%, 30%, 50%, and 100% of rated power

Practical Notes

Modern string inverters achieve European efficiencies of 96-98%. The CEC (California Energy Commission) efficiency uses different weights optimized for sunnier climates. Microinverters and power optimizers have slightly lower peak efficiency but can improve system-level efficiency by reducing mismatch losses from shading or panel variation.

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