Wiring and Protection
Wire Power Loss Calculator
Use Wire Power Loss when wire loss is the quantity you need. Enter current and circuit resistance, then compare the answer with the equipment or operating limits that apply to your case.
Calculate Wire loss
Check the source and units before calculating.
Values this page needs
Record ambient temperature, bundling, insulation class, and termination conditions. If operating conditions changed between readings, calculate separate cases.
Confirm decimal placement whenever a source uses a different unit scale. For the companion DC cable loss calculation, open Solar DC Cable Loss Calculator.
- Current
- Default example: 20 A. Enter current in A.
- Circuit resistance
- Default example: 0.25 Ω. Enter circuit resistance in Ω.
Understanding the equation
The arithmetic is based on Ploss = I²R. Its variables correspond to Current and Circuit resistance.
Using the loaded examples gives 100.00 W. Your saved case should identify where each entry came from.
Calculate wire loss from current and circuit resistance. The next worksheet may be Contact Resistance Loss Calculator if contact power loss is needed.
Using the answer downstream
Record current and circuit resistance with wire loss. Include the operating state and data source.
Carry wire loss with all available digits during downstream arithmetic. Round at the final reporting step.
What the number means
The primary answer, Wire loss, describes only the entered scenario. Compare it with ampacity, voltage-drop, fault-current, and protection limits.
Store the measurement state and conversion notes with the answer. Another relevant worksheet is Source Internal Resistance Calculator.
Before accepting the number
Unit-prefix mistakes often dominate the arithmetic error.
Verify sign, scale, and physical meaning before accepting the number.
Where this estimate can fail
Use the complete energized current path.
A broader analysis may require fault duration, protective-device curves, and conductor thermal limits. Document which effects were checked elsewhere in the analysis.
Keep one-way and round-trip lengths clearly identified. If you also need cord loss, continue with Extension Cord Power Loss Calculator.
Questions about Wire Power Loss
Can I change several inputs at once?
Change one uncertain entry at a time and preserve the baseline. Keep one-way and round-trip lengths clearly identified.
What else is required before final selection?
Use the number as one check, then review the applicable installation and equipment requirements.
What precision should move to the next worksheet?
Retain the raw result for comparison and create a separately rounded reporting value if needed.
Can an input legitimately be zero?
Use zero only when it describes the physical condition. It is not a substitute for missing data.
Which operating condition belongs in this calculation?
Measured and rated values can represent different states. Use the installed route length, conductor material, and actual current path.