What is the maximum allowable voltage drop for branch circuits according to NEC standards?

The maximum allowable voltage drop for branch circuits, as specified by the National Electrical Code (NEC), is commonly accepted to be 5%. This figure is established to ensure that electrical loads receive sufficient voltage for proper operation without causing performance issues.

To provide context, a 5% voltage drop limits the reduction in voltage reaching the load, which is important for maintaining efficiency and device longevity. Excessive voltage drop can lead to overheating, equipment malfunction, and reduced operational efficiency.

While lower percentages, like 2% or 3%, are often recommended for specific situations—such as feeder circuits or lighting circuits—the overall acceptable standard for branch circuits is set at 5%. This balance allows for practical installations while still ensuring safety and functionality. It's also important to note that scenarios where the drop might exceed this standard should be carefully evaluated to avoid complications.