8.4 Voltage Drop Requirements

The voltage drop requirement is as follows:

Voltage drop of feeder + Voltage drop of branch circuit   ≤ 5%

The maximum combined voltage drop on both installed feeder conductors and branch circuit conductors to the farthest connected load or outlet must not exceed 5 percent. This is the steady-state voltage drop under normal load conditions.

The voltage drop requirements of the following California Electrical Code (CEC) sections are exempted from the requirement of §130.5(c):

1.  Article 647, Sensitive Electronic Equipment, Section 647.4 Wiring Methods

2.  Article 695, Fire Pump, Section 695.6, Power Wiring

3.  Article 695, Fire Pump, Section 695.7, Voltage Drop

However, the informational note about voltage drop in Article 210, Branch Circuits, of the California Electrical Code is not part of the requirements of the Energy code, nor is the informational note about voltage drop in Article 215, Feeders.

Voltage drop represents energy lost as heat in the electrical conductors. The loss is called “I²R” (I-squared-R) loss, meaning that the loss is directly proportional to the conductor resistance and to the current squared. Because of I²R loss, it is advantageous to distribute utilization power at the highest practical voltage to reduce the amount of current into each load. 

Voltage drop losses are cumulative, so voltage drop in feeders and voltage drop in branch circuits add up to the load at the end of the branch circuit. Excessive voltage drop in the feeder conductors and branch circuit conductors can result in inefficient operation of electrical equipment.