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Cable I²R Power Loss Calculator

Estimate cable resistive power and annual energy losses from resistance, current, length and operating hours.

Updated September 2026

How it works

Estimate cable resistive power and annual energy losses from resistance, current, length and operating hours.

Formula:
1φ: Ploss = I²·(2RL); 3φ: Ploss = 3·I²·RL, with L in km.

Before you use the result: Resistance rises with conductor temperature; use temperature-adjusted values for accurate estimates.

Practical use

Use verified material data and project geometry. Treat results as planning estimates and compare them with the energy/thermal requirements that apply to the project.

Keep units consistent with the source information.
Use project-specific densities, pack sizes and coverage rates where provided.
Round purchasing quantities to supplier packaging and delivery rules.

How to use this calculator: Cable I²R Power Loss Calculator

Estimate cable resistive power and annual energy losses from resistance, current, length and operating hours.

Quick workflow

Enter the project values from the latest drawing, specification or verified site measurement.
Check units, material properties, allowances and any code- or supplier-specific parameters before calculating.
Review the result together with the formula, assumptions and the related checks shown on this page.

Worked example

Example inputs: System: Three phase; Current [A]: 80; One-way route length [m]: 60; Conductor resistance [Ω/km]: 0.387.

Using the sample values built into the calculator, the calculation gives approximately: Cable resistive power loss: 445.8 W; Annual cable energy loss: 1 115 kWh/year.

What the result means

Calculation method: 1φ: Ploss = I²·(2RL); 3φ: Ploss = 3·I²·RL, with L in km.

Before using the result: Resistance rises with conductor temperature; use temperature-adjusted values for accurate estimates.

Common questions

What does this calculator do?

Estimate cable resistive power and annual energy losses from resistance, current, length and operating hours.

Which inputs should I verify?

Key inputs to verify include: System, Current [A], One-way route length [m], Conductor resistance [Ω/km].

Can I use this result for final design or ordering?

Use the result as a transparent planning or checking aid. Final design, code compliance, supplier selection and project-specific decisions still need to be verified where applicable. Resistance rises with conductor temperature; use temperature-adjusted values for accurate estimates.

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