Transformer Efficiency Calculator
Estimate transformer efficiency and losses from measured input and output power over the same operating interval.
How to use this calculator
- Enter measured real input and output power in kW.
- Check that all inputs use the same units, time period and population scope.
- Change one assumption at a time when comparing scenarios.
Formula used by transformer efficiency calculator calculator
Efficiency = output power ÷ input power × 100%; losses = input − output.
- Efficiency = output power ÷ input power × 100%; losses = input − output.
- Measurements must share the same interval and system boundary. At very low loads, meter uncertainty may distort the result; output cannot exceed input in this simple passive model.
- The tool validates entered values and formats results for readability; it does not verify assumptions against external records.
Worked examples
Worked example
10 kW input and 9.65 kW output.
Efficiency = 96.5%; losses = 0.35 kW.
Estimated transformer efficiency is 96.5%, with 0.35 kW loss.
Understanding the result
Estimate transformer efficiency and losses from measured input and output power over the same operating interval.
Measurements must share the same interval and system boundary. At very low loads, meter uncertainty may distort the result; output cannot exceed input in this simple passive model.
Important notes
Measurements must share the same interval and system boundary. At very low loads, meter uncertainty may distort the result; output cannot exceed input in this simple passive model.
Treat the result as an estimate based on the entered inputs. For regulated, engineering, employment, tax or business decisions, check applicable official rules, specifications and professional guidance.
Frequently asked questions
Should reactive power be used?
Use real power for energy efficiency. Apparent power alone is not equivalent to useful transferred real power.
Does efficiency stay constant with load?
No. Core and copper losses vary with voltage, current and load.
How should I use the result?
Measurements must share the same interval and system boundary. At very low loads, meter uncertainty may distort the result; output cannot exceed input in this simple passive model.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.