Voltage Drop Distribution Calculator

For the same kVA load, a higher Source Voltage means the feeder only needs to carry a lower current to deliver that power (Load Current = Load / Source Voltage), and voltage drop depends on current -- so raising the source voltage lowers the current, which lowers the drop, and that smaller drop is also being measured as a percentage of a larger starting voltage besides.

Yes -- voltage drop is calculated as I x (R x power factor + X x sin(theta)), with both the resistance and the reactance taken directly from NFPA 70's National Electrical Code, Chapter 9 Tables 8 and 9, for copper in PVC or aluminum conduit. That matters because reactance is the only term that grows as power factor falls: a resistance-only estimate would report the drop shrinking as the power factor gets worse, which is backwards. The Table 9 reactance values describe conductors in conduit; an overhead primary feeder at typical phase spacing has roughly two to three times more reactance, so treat this as a conservative lower bound for overhead construction.

Longer conductors have more total resistance -- the resistance-per-1,000- feet value for your selected Conductor Size scales up directly with Feeder Length -- and voltage drop is directly proportional to that total resistance. Doubling the feeder length roughly doubles the calculated voltage drop for the same load and conductor size.

Single-phase feeders use a factor of 2 (accounting for the round-trip current path through both the supply and return conductor), while 3-phase feeders use a factor of √3 (about 1.73), which comes from the line-to-line voltage relationship in a balanced three-phase system. Selecting the wrong Phases option for your actual feeder will produce a meaningfully different voltage drop estimate.

Conductor Size selects resistance and reactance values for uncoated stranded copper from NEC Chapter 9 Tables 8 and 9 -- a larger conductor (like 4/0 AWG) has meaningfully lower resistance than a smaller one (like 4 AWG), so upsizing the conductor is one of the most direct ways to reduce voltage drop on a long feeder run without changing the load or feeder length.