Voltage Between Neutral and Ground: What's Normal, What Isn't

A neutral-to-ground reading puzzles people because the two wires are joined at the panel. That junction is exactly what makes the reading useful.

Short answer: at the service panel, neutral and ground are bonded together, so the voltage between neutral and ground is essentially 0 V. At an outlet it equals the voltage drop on the neutral, the circuit's return current times the neutral wire's resistance, so it reads near 0 V with nothing running and can climb to a few volts under a heavy load on a long run. The NEC sets no neutral-to-ground limit. A reading that is high with no load, out of proportion to the load, or close to line voltage points to a loose or open neutral.

Why is there voltage between neutral and ground at all?

At the service disconnect, the main bonding jumper ties the neutral to the grounding system. That is the one place they meet; grounding vs bonding covers why it happens only once. From there the two conductors run side by side to every outlet, doing different jobs:

• The neutral carries the return current of every 120-volt load, the whole time it runs.
• The equipment grounding conductor carries nothing, except during a fault.

Current through resistance produces voltage. At the outlet, the ground wire is still sitting at the potential of the bond, while the neutral has risen above it by current × resistance. That difference is what the meter shows.

It includes everything sharing that neutral path: other loads on the same circuit, the imbalance on a shared multiwire neutral, and, for a circuit fed from a subpanel, the drop along the feeder neutral back to the main panel.

Portable generators raise a separate neutral question, whether the generator's own neutral is tied to its frame, covered in generator neutral bonding.

Worked example: 12 A on 75 feet of 14 AWG

Illustrative. NEC Chapter 9, Table 8 lists 3.07 Ω per 1,000 ft for solid uncoated 14 AWG copper at 75 °C:

• Neutral resistance: 75 ft × 3.07 Ω ÷ 1,000 ft = 0.230 Ω
• Neutral-to-ground at 12 A: 12 × 0.230 = 2.76 V, about 2.8 V
• The hot conductor drops the same again, so hot-to-neutral at the outlet sags by about 2 × 2.76 = 5.5 V, or 4.6% of 120 V

The same run in 12 AWG (1.93 Ω per 1,000 ft in Table 8) has 75 × 1.93 ÷ 1,000 = 0.145 Ω of neutral resistance:

Real readings land near these numbers, not on them. The 75 feet is cable length along its actual route, not distance on a floor plan. Table 8 values are at 75 °C, so a cooler wire reads a little lower. And every splice and terminal adds a little resistance of its own.

The 5.5 V total drop is above the 3% figure in the informational note to NEC 210.19(A). That note is a recommendation, not a requirement: NEC 90.5(C) makes informational notes non-mandatory. A perfectly sound circuit can show 2.8 V neutral-to-ground under load. Run your own numbers with the voltage drop calculator.

What is a normal neutral-to-ground reading?

On the "2 volt" figure. Power-quality guidance commonly cites about 2 V under load as a comfortable ceiling for sensitive electronics, and some equipment makers ask for less. That is a rule of thumb, not a code requirement: the NEC sets no neutral-to-ground voltage limit. The worked example exceeds it on a sound circuit, which is the point. The rule of thumb is about equipment comfort and circuit length, not a pass/fail test of wiring safety. How the reading changes with load tells you more than any single number.

What causes high voltage between neutral and ground?

• A loose or deteriorating neutral connection. A loosened push-in terminal, a tired wire nut, a loose screw on the neutral bar. The added resistance shows up as extra neutral drop, and as heat, which is the fire mechanism.
• A long or heavily loaded circuit. Not a defect, just physics. Outlets at the far end of long runs read highest.
• A shared-neutral problem. On a multiwire branch circuit with both hots on the same leg, the neutral carries the sum of both loads instead of the difference, roughly doubling the drop. See what is a multi-wire branch circuit.
• Subpanel feeder drop. Circuits fed from a subpanel add the feeder neutral's drop to their own.
• An open or high-resistance neutral. The extreme end of the loose-connection case.
• An extra neutral-to-ground connection downstream, such as a bonded subpanel or a jumper at a receptacle. Code forbids any such connection past the service disconnect (NEC 250.24(A)(5) and 250.142(B)). It tends to make readings misleadingly low at the point of the bond while return current flows on grounding conductors. See subpanel grounding and neutral separation.

How to measure neutral-to-ground voltage safely

Measure at a receptacle only, through its slots. Never with the cover plate off, and never inside the panel.

Use a multimeter set to AC volts, rated at least CAT II for the voltage (receptacle circuits fall in CAT II; most electrician meters are CAT III or higher), with leads in good condition.

1. Hot to neutral (narrow slot to wide slot). This confirms the meter works and gives line voltage, around 120 V.
2. Neutral to ground (wide slot to round hole) with nothing running on that circuit. Expect close to zero.
3. Add a known load on the same circuit and repeat both readings. A 1,500 W space heater on high draws 1,500 ÷ 120 = 12.5 A; plug it into the other half of the duplex.
4. Compare. Neutral-to-ground should rise roughly as the math predicts, and hot-to-neutral should sag by about twice that rise. If hot-to-neutral sags much more, the extra drop is on the hot side, such as a loose hot terminal or breaker connection. If neutral-to-ground rises far more than predicted, the problem is on the neutral.
5. Unplug the load once you've read it. Stop immediately if anything is warm or smells hot.

A digital meter touching a disconnected wire can show a misleading "ghost" reading. A low-impedance (LoZ) mode, where the meter has one, loads that phantom voltage down. One CAT III meter with a LoZ mode:

We earn a commission if you buy through links on this page, at no extra cost to you. It does not change what we recommend — see our affiliate disclosure. As an Amazon Associate I earn from qualifying purchases.

Why is this electrician work?

Measuring at an outlet is a safe homeowner diagnostic. Fixing what it finds is not. Remaking neutral connections means opening boxes on a circuit where the neutral can be energized through connected loads, and the neutral bar sits inside an enclosure whose service conductors stay live with the main breaker off.

Write down both readings and the load you used; it shortens the electrician's visit.

Standards and code reference

• NEC 250.24(B): the main bonding jumper connects the neutral to the grounding system at the service
• NEC 250.24(A)(5): no neutral-to-ground connection on the load side of the service disconnect
• NEC 250.142(B): the neutral may not be used to ground equipment downstream of the service disconnect, with narrow exceptions
• NEC Chapter 9, Table 8: conductor properties, including the DC resistance values used in the worked example
• NEC 210.19(A), informational note: the 3% branch-circuit and 5% total voltage-drop recommendation; informational, not mandatory, per NEC 90.5(C)
• IEC/UL 61010 series: safety standards for test instruments, including the CAT II and CAT III measurement categories

Code editions and local amendments vary. Confirm the adopted edition with your AHJ, and treat manufacturer instructions as governing wherever they are more restrictive.

Where to go next

• Breaker torque and loose connections
• What is a bootleg ground?
• Wire gauge explained
• Outlet not working: troubleshooting

More in our electrical panel guides.