The Efficiency Calculator helps measure how effectively a system converts input energy into useful output energy or work. This tool is essential in engineering, manufacturing, electronics, and many industrial applications where energy conservation and performance tracking matter.
Belonging to the power and energy calculator category, it evaluates how much of the supplied energy gets used for the intended purpose, and how much gets wasted due to losses like friction, heat, or electrical resistance. Efficiency is expressed as a percentage and indicates the system’s performance in real-world operating conditions.
formula of Efficiency Calculator
η = (P_out / P_in) * 100
Where:
- η = Efficiency (as a percentage)
- P_out = Useful power output (watts, or joules/second)
- P_in = Total power input (watts, or joules/second)
How to find P_out and P_in:
P_out = W_useful / t
P_in = W_total / t
- W_useful = Useful energy or work delivered (in joules)
- W_total = Total energy supplied, including losses (in joules)
- t = Time in seconds
Including system losses:
P_in = P_out + P_losses
Where:
P_losses = P_friction + P_heat + P_electrical + P_other
- P_friction = Power lost to friction (watts)
- P_heat = Power lost as heat (watts)
- P_electrical = Power lost due to electrical resistance (watts)
- P_other = Other system-specific losses (watts)
This extended formula is useful for understanding where energy losses occur, so you can take action to improve system efficiency.
Common Reference Table
| Term | Description | Formula or Example Use |
|---|---|---|
| Efficiency (η) | % of useful power compared to total input | η = (P_out / P_in) * 100 |
| P_out | Useful output power | P_out = W_useful / t |
| P_in | Total input power | P_in = W_total / t |
| W_useful | Output energy or work | e.g., 600 joules of mechanical energy |
| W_total | Supplied energy, including losses | e.g., 800 joules of electrical energy |
| P_losses | Energy wasted due to inefficiencies | P_losses = P_heat + P_friction + … |
| Energy Conversion | Convert between units (J, kWh, cal, etc.) | 1 kWh = 3.6 million joules |
| Power Conversion | Convert horsepower, watts, and BTUs | 1 HP = 745.7 watts; 1 BTU/hr = 0.2931 watts |
This table helps users quickly understand and apply common terms without having to calculate each one manually.
Example of Efficiency Calculator
Scenario:
A motor receives 1000 joules of electrical energy and delivers 700 joules as useful mechanical work in 10 seconds.
Step 1: Calculate Input and Output Power
P_in = W_total / t = 1000 / 10 = 100 watts
P_out = W_useful / t = 700 / 10 = 70 watts
Step 2: Plug values into the formula
η = (P_out / P_in) * 100
η = (70 / 100) * 100 = 70%
Result:
The motor is 70% efficient, meaning 30% of the input energy is lost as heat or other forms of waste.
Most Common FAQs
It depends on the system. Electrical appliances often have 80% to 95% efficiency, while engines may range from 25% to 40%. Higher efficiency means less energy is wasted.
No. Efficiency over 100% would mean the system outputs more energy than it receives, which violates the law of conservation of energy. However, in rare cases of misleading calculations or units, values might appear that way—always double-check your inputs.