Solar Cable Voltage Drop Calculator & Wire Size Guide
Calculate solar cable voltage drop and find a suitable wire size for your PV system. Select the conductor material, cable size, one-way length, current, and system voltage to calculate voltage drop, voltage loss percentage, and load-end voltage for DC, single-phase AC, and three-phase circuits.
01
What Is Voltage Drop?
Voltage drop is the reduction in electrical potential that occurs as current flows through the resistance of a conductor. Every cable has inherent electrical resistance. As current travels along a conductor, part of the electrical energy is dissipated as heat, causing the voltage measured at the load end to be lower than the source voltage.
In solar PV systems, excessive voltage drop can reduce the voltage delivered to an inverter or other equipment, increase conductor losses, and reduce the amount of usable electrical power delivered by the system.
The magnitude of voltage drop is primarily determined by four factors:
-
Conductor size: A larger conductor has a greater cross-sectional area and lower resistance, resulting in lower voltage drop.
-
Cable length: Resistance increases with conductor length. For the same conductor size and current, doubling the one-way cable length approximately doubles the voltage drop.
-
Operating current: Voltage drop increases as current increases. Higher current produces greater losses through the conductor's resistance.
-
Conductor material: Copper generally has lower electrical resistivity than aluminum, so a copper conductor of the same nominal size typically produces less voltage drop under equivalent conditions.
02
How to Use the Voltage Drop Calculator
Use the calculator to estimate voltage drop and identify a suitable conductor size for solar PV, battery, residential AC, and commercial three-phase circuits. Enter the following parameters:
-
Conductor Material — Select Copper or Aluminum. Copper has lower electrical resistivity and therefore produces less voltage drop for the same conductor size and length. Aluminum can provide a cost-effective alternative when the conductor is appropriately sized for the application.
-
Wire Size — Select the conductor size in AWG or kcmil. Larger conductors have greater cross-sectional area and lower resistance, which generally results in lower voltage drop.
-
Circuit Type — Select DC, Single-Phase AC, or Three-Phase AC. The calculator applies the appropriate circuit factor when determining voltage drop. DC is commonly used for PV source circuits and battery systems, while single-phase and three-phase options are intended for AC circuits.
-
One-Way Circuit Length — Enter the cable distance in one direction, such as from a solar array to an inverter or from an inverter to a main distribution panel. For DC and single-phase circuits, the calculator accounts for the complete circuit path automatically. Do not enter the total round-trip distance.
-
Load Current — Enter the current flowing through the circuit in amperes (A). For a solar PV source circuit, the calculator can determine design current from the module Isc and the number of parallel strings. For an inverter AC circuit, use the applicable design or maximum continuous output current.
-
Source Voltage — Enter the nominal voltage at the beginning of the circuit. This may be the DC operating voltage of a PV string or battery system, or the nominal AC voltage of an inverter or electrical distribution system, such as 208 V, 240 V, or 480 V.
What the Calculator Provides
After the inputs are entered, the calculator provides several key results:
-
Voltage Drop (V) — The calculated voltage reduction across the selected cable run.
-
Voltage Drop (%) — Voltage drop expressed as a percentage of the source voltage. This allows the result to be compared with the project's specified voltage-drop target.
-
Voltage at Load End (V) — The estimated voltage available at the receiving end of the circuit after accounting for conductor voltage drop.
-
Conductor Area — The cross-sectional area of the selected conductor, expressed in circular mils and/or metric conductor area where applicable.
Voltage Drop Tables
Explore our Voltage Drop Tables to quickly determine the correct wire size based on distance, current, and system voltage. This tool helps you minimize power loss, improve efficiency, and ensure compliance with electrical standards—especially critical for solar and industrial installations. Use it alongside our Wire Gauge Chart for a complete cable sizing reference.
