Voltage Drop and Cable Size Calculator for ELV Solar Power Systems
This calculator determines the voltage drop (in mV/A.m) in a circuit with the given characteristics (allowable voltage drop, cable run length, maximum current demand, system voltage), and recommends a suitable cable size to ensure that this level of voltage drop is not exceeded. Cable size recommendations are based on Australian Standard AS3000.
Note that this calculator does not consider current carrying capacity. In most cases, voltage drop is a more significant consideration in ELV circuits, with cables satisfying voltage drop requirements automatically satisfying current carrying requirements. The main exception to this rule of thumb can be high current cables attached to batteries.
Allowable Voltage Drop (%): The percentage of voltage drop acceptable. This is usually 5% or lower in ELV systems.
Run Length (m): The total cable length of the circuit. Don't forget to include return cable runs where necessary.
Maximum Current Demand: Defined in AS4509.2 as "The maximum 30 minute average of apparent power or DC power consumption (measured in volt-amperes for AC and watts for DC)". The maximum current that the cable is expected to carry.
System Voltage (V): the nominal system voltage, typically 12, 24 or 48 volts for residential ELV systems.
This calculator is accurate but is intended as a guide only. We recommend that you independently verify any results obtained before using them.