Efficiency

Formula

Description

Efficiency is the ratio of useful output power to total input power, expressed as a decimal between 0 and 1 (or as a percentage when multiplied by 100). The difference between input and output power is wasted, typically as heat. Every power conversion stage in a system has its own efficiency, and the overall system efficiency is the product of all individual stage efficiencies. For example, two 90% efficient stages in series give only 81% overall efficiency. This cascading effect makes each stage's efficiency critically important in multi-stage power systems.

Variables

• η — Efficiency ratio (0 to 1, dimensionless)
• Pout — Output power delivered to the load (W)
• Pin — Input power consumed from the source (W)

Practical Notes

Modern switching regulators achieve 85-95% efficiency. Linear regulators are limited to η = Vout/Vin. Class D audio amplifiers reach 90%+, while Class A/B manage 50-70%. Solar panel efficiency ranges from 15-25% for commercial panels. Always account for efficiency when sizing power supplies and thermal management.