Using Voltage Drop Calculators to Your Advantage

June 5, 2023
Paul Abernathy

All electrical conductors will have some internal resistance to current flow, and running a current through this direct current (DC) resistance causing the voltage to drop. In alternating current (AC) systems, the conductors experience impedance which is the opposition to current flow in the conductors. As the length of the wire-type conductors and/or cable increases, so does its impedance - the overall reactance increases in proportion to the voltage drop increases.

Why Does it Matter?

Voltage drop is particularly problematic in long conductor and/or cable runs; For example, with large, commercial-electrical projects, the raceways can travel long distances from its original termination point in the electrical cabinet to the end load point. This resulting voltage drop can easily be calculated with a voltage drop calculator.

Voltage drop is calculated as the amount of actual voltage loss that occurs through all parts of a circuit due to what is called "impedance". While a copper and/or aluminum conductor inherently have resistance, the overall impedance is a collection of factors that inherently resist the flow of current thus affecting the overall voltage as well.

What are the Negative Effects? 

When your installation results in voltage drop that exceeds the recommended allowance of 3% for branch circuits, it can cause the following:

  • lights to flicker or glow dimly
  • resistance style heating units to heat improperly
  • electric motors to run inefficiently

These inefficiencies can result in hotter than normal tested parameters leaving the wire susceptible to early burn out. This condition causes the load to work harder with less voltage pushing the current from the source to the end load.

The Solution?

Encore Wire always recommends taking voltage drop into consideration to ensure the most efficient and cost-effective installation possibly. The electrician can ensure a safe, long lasting, and efficient installation of branch circuit, feeder, and service conductors as it pertains to voltage drop by using our free online voltage drop calculator.  


Paul Abernathy, CMECP
Manager of Codes and Standards
Encore Wire

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