What is acceptable voltage drop on a 240V circuit?

Most engineers target 3% or less on branch circuits. Over 5% total (feeder plus branch) is generally considered poor practice. Check your local authority having jurisdiction.

What wire size should I use for a 240V circuit?

Wire size depends on load current, run length, and acceptable voltage drop. Use the voltage drop calculator linked above to find the right gauge for your specific run.

Voltage Drop at 240V (Single-Phase AC)

240V single-phase powers larger appliances like dryers, ranges, water heaters, and EV chargers. Two hot conductors and (usually) a neutral are used.

Open 240V Voltage Drop Calculator with Example Values →

Why 240V Systems Need Attention

At 240V, voltage drop matters on longer runs. A 3% drop on a 120V circuit is only 3.6V, but a load expecting 120V may run noticeably hotter or dimmer at 116V.

Example Calculation

For a 240V Single-Phase AC circuit at 30 A over 80 ft using 10 AWG copper:

Voltage drop = 2 x I x R = 2 x 30 x (ohms per ft for 10 AWG x 80 ft)

Run this example in the calculator →

Common Applications at 240V

Clothes dryers
Electric ranges
Water heaters
Level 2 EV chargers
Air conditioners

Common Questions

What is the acceptable voltage drop for a 240V circuit?

Most engineers target 3% or less on branch circuits and 5% total (feeder plus branch). These are general guidelines, not hard NEC requirements. Check your local code.

What wire gauge should I use for a 240V circuit?

It depends on load current and run length. Use the voltage drop calculator with your specific values. A longer run or heavier load requires a larger gauge.

Does voltage drop affect safety?

Excessive voltage drop can cause motors to overheat, breakers to nuisance-trip, and equipment to malfunction. It is not just an efficiency issue.

Can I use aluminum wire on a 240V circuit?

Aluminum is commonly used for larger feeders (service entrances, subpanel feeds). For small branch circuits, copper is generally required. Aluminum has higher resistance than copper for the same gauge, so voltage drop is worse for the same wire size.