Wire Power Loss Calculator
Estimate conductor I-squared-R power loss and its annual energy cost for single-phase or balanced three-phase current.
Enter conductor and load values
Conductor power loss
About this calculator
Estimate conductor I-squared-R power loss and its annual energy cost for single-phase or balanced three-phase current.
Assumes equal current and resistance in all phase conductors and uses resistance-only loss. It excludes neutral current, harmonics, reactance, varying load profiles, and upstream equipment losses.
Method and assumptions
Single-phase loss = 2 × I² × R × one-way length. Balanced three-phase loss = 3 × I² × R × one-way length. The result uses the entered per-conductor AC resistance per 1,000 ft; annual energy and cost use the entered operating schedule and rate.
Resistance values use the site’s listed 75°C AC conductor data. Temperature adjustment is a first-order estimate; measured or manufacturer values for the installed conductor take precedence.
FAQs
Are listed conductor resistance values exact for an installed circuit?
No. Actual resistance depends on conductor construction, operating temperature, installation, connections, and parallel arrangement. Use project-specific manufacturer or engineering data when available.
Does this verify conductor ampacity or code compliance?
No. These tools estimate resistance, I-squared-R loss, or cumulative voltage drop only. Ampacity, conductor sizing, protection, installation, and local requirements need separate review.
Sources
Conductor resistance data is attributed in the calculation registry to Southwire cable specifications; verify conductor-specific data for the installed cable.