Voltage Drop Intro

Voltage Drop

Solar Design Calculator: Analyze voltage drop for PV source circuits, AC single-phase, and three-phase output circuits. Calculate losses with temperature-corrected resistance values, ensure NEC 690.8 compliance, and optimize conductor sizing for all circuit lengths (with enhanced impedance calculations for AC runs over 100 feet).

Circuit Configuration

Circuit Type *

Connection Type *

For DC circuits only

Number of Strings

For parallel DC only

Electrical Parameters

Current (A) *

Imp for DC, Iac for AC

Voltage (V) *

Vmp for DC, Vac for AC

Power Factor

For AC circuits (typical: 0.85-0.95)

Grid Frequency

For AC circuits over 100 ft

Conductor Specifications

Wire Size *

Conductor Material *

One-Way Length (ft) *

Distance from source to load

Ambient Temperature *

Voltage Drop Percentage

Voltage Drop

Delivered Voltage

Calculation Details

About Voltage Drop and NEC 690.8

Voltage drop in conductors reduces system efficiency and can impact equipment performance. Per NEC 690.8(B)(1), maximum voltage drop should not exceed 3 percent for PV source and output circuits. Higher voltage drop results in power loss, reduced energy production, and potential equipment issues. Proper conductor sizing minimizes losses while balancing installation costs. For long circuit runs, consider using larger wire gauges, higher system voltages, or reducing circuit length. Temperature, conductor material, and circuit configuration all affect voltage drop calculations. Always verify calculations meet both NEC requirements and manufacturer specifications.