What is the maximum voltage drop recommended for branch circuits and feeders/electrical systems in the National Electrical Code (NEC)?

What is the maximum voltage drop recommended for branch circuits and feeders/electrical systems in the National Electrical Code (NEC)?

• A. 1% branch / 2% feeder/system
• B. 2% branch / 4% feeder/system
• C. 3% branch / 5% feeder/system
• D. It is recommended that no voltage drop be allowed in the system.

Answer: (C)

Voltage drop is the voltage that is lost as current flows through conductors due to their resistance. The NEC provides practical guidelines to keep end devices operating within a healthy voltage range, even as length, load, and conductor size vary. The recommended limits are 3% for branch circuits and 5% for feeders (and the overall system). This means a 120 V nominal system should still deliver around 116.4 V or more at the farthest point on a branch circuit, and no more than about 114 V at the farthest point fed through a feeder, under typical full-load conditions. Branch circuits are typically shorter and serve individual outlets, so keeping the drop tighter helps ensure lights and receptacles perform reliably. Feeders may run longer to subpanels serving multiple circuits, so a slightly higher allowance is acceptable while still keeping the total voltage drop within a practical range. In practice, you can control voltage drop by using larger conductors, shorter runs, or routing to minimize length and optimize load distribution. Zero drop isn’t realistic in electrical systems, so these percentages provide workable targets to maintain device performance and comfort.

Voltage drop is the voltage that is lost as current flows through conductors due to their resistance. The NEC provides practical guidelines to keep end devices operating within a healthy voltage range, even as length, load, and conductor size vary. The recommended limits are 3% for branch circuits and 5% for feeders (and the overall system). This means a 120 V nominal system should still deliver around 116.4 V or more at the farthest point on a branch circuit, and no more than about 114 V at the farthest point fed through a feeder, under typical full-load conditions. Branch circuits are typically shorter and serve individual outlets, so keeping the drop tighter helps ensure lights and receptacles perform reliably. Feeders may run longer to subpanels serving multiple circuits, so a slightly higher allowance is acceptable while still keeping the total voltage drop within a practical range. In practice, you can control voltage drop by using larger conductors, shorter runs, or routing to minimize length and optimize load distribution. Zero drop isn’t realistic in electrical systems, so these percentages provide workable targets to maintain device performance and comfort.