Efficiency
η = Pout / Pin
Quick answer
This calculator solves η = Pout / Pin for Efficiency. With Output Power 10 W, Input Power 22 W, the result is 45.45 %. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
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.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| eta | Efficiency | — | —, % |
| Pout | Output Power | W | µW, mW, W, kW |
| Pin | Input Power | W | µW, mW, W, kW |
Step by step
- 1. What you know: Output Power 10 W, Input Power 22 W
- 2. The relation: η = Pout / Pin
- 3. Substitute: Pout = 10 W, Pin = 22 W
- 4. Result: Efficiency = 45.45 %
Worked examples
Minimum range
Given: Output Power 10 mW, Input Power 22 mW
Result: Efficiency = 45.45 %
Low range
Given: Output Power 100 mW, Input Power 0.22 W
Result: Efficiency = 45.45 %
Typical
Given: Output Power 10 W, Input Power 22 W
Result: Efficiency = 45.45 %
High range
Given: Output Power 1 kW, Input Power 2.2 kW
Result: Efficiency = 45.45 %
Maximum range
Given: Output Power 10 kW, Input Power 22 kW
Result: Efficiency = 45.45 %
Solving for each variable
Solve for Efficiency
Output Power 10 mW, Input Power 22 mW → 45.45 %
Solve for Output Power
Efficiency 2.5 %, Input Power 22 mW → 0.55 mW
Solve for Input Power
Efficiency 2.5 %, Output Power 10 mW → 0.4 W
How Efficiency changes with Output Power
| Output Power (input) | Efficiency (result) |
|---|---|
| 1 W | 4.545 % |
| 2.5 W | 11.36 % |
| 5 W | 22.73 % |
| 7.5 W | 34.09 % |
| 10 W | 45.45 % |
| 15 W | 0.6818 |
| 20 W | 0.9091 |
| 40 W | 1.818 |
| 70 W | 3.182 |
| 100 W | 4.545 |
The same result in other units
| Unit | Value |
|---|---|
| 0.4545 | |
| % | 45.45 |
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<p><a href="https://vbatpower.com/formulas/efficiency/">Efficiency</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Efficiency?
Use η = Pout / Pin. With Output Power 10 W, Input Power 22 W, Efficiency works out to 45.45 %.
What is the formula for Efficiency?
The formula is η = Pout / Pin. 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).
How do you find Output Power when you know the other values?
Rearrange for Output Power: with Efficiency 2.5 %, Input Power 22 mW, Output Power is 0.55 mW.
How do you find Input Power when you know the other values?
Rearrange for Input Power: with Efficiency 2.5 %, Output Power 10 mW, Input Power is 0.4 W.
What units does Efficiency use?
Efficiency is shown in , %. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
All Power & Efficiency formulas →Need more features?
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