Quick answer
A hot wire is the ungrounded conductor in a circuit that carries voltage from the panel to a light, outlet or appliance; in US homes it sits at 120 volts to ground and is usually black or red, though any color except white, gray or green is allowed.
It is the wire a switch or breaker opens to turn power off. Touching it while also touching ground or the neutral completes a path through the body, which is why every wire should be treated as live.
Quick facts
The key facts about Hot Wire, with sources:
- NEC name
- Ungrounded conductor
- Allowed colors
- Any color except white or gray (reserved for neutrals, 200.6 and 200.7) and green (250.119) 13
- Voltage in homes
- 120 V to ground on each leg; 240 V between the two hot legs
- Terminal
- The brass screw on a receptacle; black lead on many devices 4
- Switched by
- Breakers and switches open the hot, not the neutral
Key takeaways
- The hot wire carries voltage from the panel to the load; it is the “live” wire.
- It is usually black or red, but any color except white, gray or green may be a hot.
- Each hot leg in a home is 120 volts to ground; two hots together make 240 volts.
- Switches and breakers interrupt the hot so the device downstream is de-energized.
- Treat every wire as hot; wiring work belongs to a licensed electrician.
What the hot wire is
In any circuit, one wire brings the voltage and another takes the current back, and the wire that brings it is the hot. The NEC calls it the ungrounded conductor, because unlike the neutral, it is not connected to earth at the service.
In a standard home cable the black wire is the hot, and in a cable for a 240-volt load or a three-way switch, a red wire is often a second hot.
The code does not require black or red; it only reserves white and gray for grounded conductors and green for grounds, so any other color is available for a hot 3.
On a receptacle, the hot goes on the brass screw and feeds the short slot 4.
How the hot wire delivers power
Your service has two hot legs from the utility transformer, each 120 volts to the neutral and to ground. A 120-volt circuit uses one hot leg and the neutral, while a 240-volt circuit uses both hot legs, which are 240 volts apart.
The breaker sits on the hot, so when it trips or is switched off, it opens the hot and the circuit goes dead downstream, and a wall switch does the same for a light.
Polarity matters for that reason: if a switch were wired into the neutral, the light would go off but the fixture would still be connected to a live hot.
Power delivered is voltage times current, so on a 120-volt circuit a hot wire carrying 10 amps delivers 1,200 watts. The wire size calculator shows which gauge safely carries the current a hot will see.
Watts = Volts × Amps · 120 V × 10 A = 1,200 W
Volts- 120 V on one hot leg; 240 V across two hots
Amps- Current flowing on the hot wire
Watts- Power delivered to the load
Kinds of hot conductors you will hear about
| Name | What it is | Typical color |
|---|---|---|
| Line (supply) hot | Hot coming from the panel into a box | Black |
| Load (switched) hot | Hot leaving a switch toward the light | Black or red |
| Second hot leg | The other leg for a 240 V circuit | Red |
| Traveler | Hot wires between three-way and four-way switches | Often red and black |
| Re-identified white | A white wire used as a hot in a cable and re-marked | White marked with tape or paint of another color 3 |
Example: reading the wires in common cables
Wire colors in common cables follow typical layouts in US residential cable, but your home may differ, and colors alone never prove which wire is hot.
| Cable or circuit | Hot conductor(s) | Other conductors |
|---|---|---|
| 120 V outlet circuit | Black | White neutral, bare ground |
| 240 V water heater | Black and red (or black and re-marked white) | Bare ground |
| 120/240 V dryer or range | Black and red | White neutral, bare or green ground |
| Three-way switch run | Black common; red and black travelers | White neutral, bare ground |
| Conduit run | Any color except white, gray or green 1 | White or gray neutral, green ground |
Colors tell an electrician what a wire is supposed to be, but only a meter confirms what it actually is, which is why a voltage tester is used before any wiring is touched.
Where hot wires run in your home
Hot wires start at each breaker in the panel and run to every outlet, switch and fixture on that circuit. In a switch box, you may find a line hot from the panel and a load hot to the light. In a fixture box, the hot connects to the black lead of the fixture.
Some boxes contain hots from more than one circuit, so turning off one breaker may leave other hots in the same box live. Older homes can have surprises, such as a white wire used as a hot without re-marking.
Large appliances have their own hots: a dryer, range or Level 2 EV charger uses two hot legs on a two-pole breaker, so both handles move together.
A 240-volt water heater may have no neutral at all, only two hots and a ground. Even with one leg off, the other can still be live, which is another reason two-pole breakers are tied.
- BreakerHot leaves the panel
- Switch boxLine hot in
- SwitchOpens or closes the hot
- Load hotTo the fixture
- FixtureReturns current on the neutral
Why the hot is handled the way it is
- Switching the hot leaves the fixture dead when the switch is off.
- Reserved colors stop a hot from being mistaken for a neutral or ground 3.
- Breakers on the hot protect the wire from overload and short circuits.
- Correct polarity keeps lamp shells and appliance casings on the safe side.
Limits of color and switches
Color is a convention, not proof, because a wire can be mislabeled or re-used, and only testing proves a wire is dead.
A switch in the off position removes power from the light but not from the box, because the line hot from the panel is still live inside. Only the breaker, confirmed with a tester, de-energizes the circuit.
Hot vs neutral vs ground
The hot brings voltage, and the neutral carries current back. The ground carries current only during a fault, and only the hot is switched.
What drives the cost of hot-wire problems
We do not print prices. A loose hot at one device is a small repair, while a damaged hot inside a wall, a burned panel connection or reversed polarity across many outlets takes more time. See the project cost tool and our electrical repair page.
How electricians make a hot wire safe to work on
The steps below describe how an electrician handles a hot wire so you know what to expect; they are not a guide to doing it yourself.
- Identify the circuit and turn off its breaker.
- Verify the tester works on a known live source.
- Test every wire in the box, since several circuits may share it.
- Re-test the tester on a known live source.
- Only then touch conductors; restore power and test when done.
What owners can do safely
Why hot wires are dangerous, and warning signs
A person who touches a hot wire and anything grounded, including a damp floor, pipe or metal box, becomes part of the circuit. OSHA’s grounding guidance notes that grounding gives current a path away from people, but a break can occur without the user’s knowledge 5.
Warning signs: sparks at a switch or outlet, a buzzing box, scorch marks, exposed copper at a device, or a tester that shows voltage on a wire you expected to be dead.
Treat every wire as live
Do not touch exposed wires, and remember that turning off a switch does not make a box safe.
If you see damaged wiring, sparks or scorch marks, keep people away, turn off the breaker if you can do so safely, and call an electrician.
If someone is shocked, do not touch them while they are in contact with the source; call 911.
Code rules
NEC 200.7 bars white and gray for ungrounded conductors, and 250.119 reserves green for grounding; beyond that, hot colors are not dictated by the NEC, though local practice uses black, red and blue 3.
EC&M also notes that the NEC does not permit white or gray insulation for ungrounded conductors in a raceway, and that in older work a gray wire may have been used as a hot, so test before trusting color 1.
A white conductor in a cable may serve as a hot only if re-identified with a color other than white, gray or green 3.
Switching devices must interrupt the ungrounded conductor; neutrals at lighting switch locations are covered by 404.2(C) 2, and your state and city adopt the NEC edition that applies.
Hot wire compared with other conductors
| Conductor | NEC name | Color | Switched? |
|---|---|---|---|
| Hot | Ungrounded conductor | Black, red, others | Yes |
| Neutral | Grounded conductor | White or gray | No |
| Equipment ground | Equipment grounding conductor | Bare, green, green/yellow | Never |
| Traveler | Ungrounded conductor | Often red/black | By three-way and four-way switches |
Myths about hot wires
- Myth Only black wires are hot.
- Reality Any color except white, gray or green may be hot 1.
- Myth A switched-off light means the box is dead.
- Reality The line hot from the panel is still live in the box.
- Myth A white wire is never hot.
- Reality It may be, if re-identified, and sometimes when it should have been but was not.
- Myth Rubber shoes make touching a hot safe.
- Reality No; any path to ground, including through a hand to a pipe, can kill.
Who may work on wiring where you live
What to do if you find an exposed or damaged hot
Your job is to make the area safe and get help, not to repair it.
- If Sparks, smoke or burning smell
- Then Leave the area; call 911 if there is fire
- If Exposed wire, no sparks
- Then Keep people away; turn off the breaker if safe; call an electrician
- If Outlet or switch warm
- Then Stop using it; call an electrician
- If Tester shows voltage where you expected none
- Then Stop; call an electrician
Know your panel
A labeled panel saves time in an emergency, and our electrical safety page and the home safety check walk through what to keep ready.
Questions about Hot Wire
What color is the hot wire?
Usually black, with red for a second hot, though the NEC allows any color except white or gray, which are for neutrals, and green, which is for ground. In older homes a white wire may also be used as a hot.
Which wire is hot, black or white?
In standard cable, black is hot and white is neutral. Colors are a convention, though, and a white wire can be re-identified as a hot, so only a tester confirms which wire is live.
Is the red wire hot?
Usually, yes: red is commonly the second hot in a 240-volt circuit, a traveler in a three-way switch circuit, or a switched hot, so treat it as live until tested.
What is the difference between line and load?
Line is the hot coming from the panel into a device, and load is the hot leaving the device toward the light or downstream outlets. Smart switches and GFCI receptacles mark these terminals separately.
How many volts is a hot wire?
In US homes, each hot leg is 120 volts to ground and to neutral, and two hot legs together give 240 volts for large appliances.
Why is the hot wire switched instead of the neutral?
Switching the hot removes voltage from the fixture when the switch is off. If the neutral were switched, the fixture would stay connected to a live hot even with the light off, which is a shock risk.
Is the wire still hot if the switch is off?
The wire from the panel into the switch box stays live, and only turning off the breaker, and confirming with a tester, makes the circuit dead.
Can a hot wire touch the ground wire?
It should not, and if it does, that is a ground fault. A properly grounded circuit will trip its breaker or GFCI, and repeated trips mean an electrician should find the fault.
What does it mean when a tester shows a wire is hot?
It means voltage is present, so do not touch it, and keep in mind that non-contact testers can also give false readings, so electricians confirm with a meter. If you were not expecting voltage at that spot, call an electrician.
Can I touch a hot wire if I am wearing rubber gloves?
No. Ordinary gloves are not rated electrical protection, and contact through any path to ground can kill, so leave live wiring to licensed electricians with rated equipment and procedures.
Sources
- EC&M, Code Q&A: Identification of Circuit Conductors (200.6, 250.119), retrieved .
- Electrical Association (Minneapolis), 2023 NEC Update Part 3 training slides, 404.2(C) Switches Controlling Lighting Loads, retrieved .
- EC&M, Code Q&A: NEC Requirements for Conductor Identification (2023), retrieved .
- Leviton, T5835-W 20A Tamper-Resistant USB Receptacle specifications (terminal identification), retrieved .
- OSHA Construction eTool, Electrical Incidents: Grounding, retrieved .
- US CPSC, Home Electrical Safety Checklist (Pub 513), retrieved .
- Texas Department of Licensing and Regulation, 2023 National Electrical Code is almost here, retrieved .
- Washington State Register WSR 25-23-069 (L&I adopts the 2026 NEC), retrieved .
Expert review
Written by the HyreElectrical Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Color rules follow EC&M on NEC 200.7, 250.119 and re-identification; terminal markings follow the Leviton T5835 data sheet; grounding and shock context follows OSHA and CPSC. Power arithmetic is labeled, and the professional verification steps describe practice, not DIY instructions, and no prices appear under G-COST.
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