HOW-TO GUIDE
Why Does My Multimeter Read 120V Instead of 240V?
By the OhmSavvy Research Team ·
Safety: 240 V circuits can kill
- A 240 V circuit delivers twice the voltage of an ordinary outlet, and the circuits that use it (dryers, ranges, water heaters, EV chargers, air conditioners) are fed by large breakers that can sustain a serious arc. Treat every terminal as live until proven otherwise.
- Use a meter and leads rated at least CAT III 600V, with intact insulation and finger guards. Keep your fingers behind the guards, wear safety glasses, and keep one hand away from grounded metal where you can.
- Only measure at receptacles you can reach without removing covers. Opening a breaker panel, removing a dead front or working on a meter base is for licensed electricians and the utility, not homeowners.
- If one leg is missing, lights brighten and dim, anything smells hot or a breaker or receptacle is discolored, switch off large appliances, and call an electrician. Call the utility first if the whole house is affected or a service wire is down, and 911 if there is smoke, fire or a person in contact with a live conductor.
How 120 V and 240 V share one supply
Most US homes get a single-phase, three-wire service usually called split-phase. The utility transformer's secondary winding has a tap at its midpoint. That center tap becomes the neutral and is bonded to ground at the service. The two ends of the winding become the hot legs, often called L1 and L2. Each half of the winding produces a nominal 120 V, and because the two ends swing in opposite directions at every instant, the full winding produces a nominal 240 V from end to end.
That gives three meaningful readings at any 240 V point: L1 to neutral, L2 to neutral and L1 to L2. The first two are about 120 V; the third is about 240 V. A reading of 120 V is therefore only "wrong" if you took it between L1 and L2. Ordinary outlets use one leg and neutral, so they read 120 V. Large appliances connect across both legs, and some also use the neutral to run 120 V controls.
Real voltages vary with load and the utility's regulation. ANSI C84.1, the standard US utilities generally follow, gives a normal service range of roughly 114 to 126 V for a 120 V service and 228 to 252 V for a 240 V one, so readings like 118 V and 237 V are both healthy. If you are new to AC readings, our explainer on AC vs DC voltage covers what the meter is showing.
Why a multimeter reads 120 volts instead of 240: causes at a glance
| Symptom | Likely cause | How to check | Fix or who to call |
|---|---|---|---|
| About 120 V, one probe on a slot that isn't a hot | Measuring hot to neutral or hot to ground | Identify the two hot terminals on the receptacle and re-probe hot to hot | Nothing to fix; the supply is normal |
| 240 V receptacle reads about 120 V hot to hot; one hot near 0 V to neutral | Lost leg: failed breaker pole, burnt bus or connection, or a utility fault | Measure each hot to neutral (step 3); check whether half the house is out | Electrician for breaker or wiring; utility if many circuits are affected |
| One hot reads normally, the other shows 20 to 90 V | Lost leg with backfeed through a 240 V load left on | Switch off large 240 V loads and re-measure | Same as a lost leg; leave large loads off until repaired |
| About 208 V hot to hot | Three-phase 120/208 V building supply | Check the building type and the appliance nameplate | Normal; use appliances rated for 208 V |
| Hot-to-neutral readings unequal (e.g. 95 V and 145 V) but hot to hot normal | Loose or failing neutral | Compare both legs to neutral with some loads on | Urgent: switch off sensitive equipment and call the utility or an electrician |
| Near 0 V hot to hot, both hots about 120 V to neutral | Both hots fed from the same leg | Check whether the circuit uses two single-pole breakers | Electrician to rewire to a proper double-pole breaker |
| Generator outlet reads 120 V or 0 V between hots | Generator voltage selector on 120 V only | Check the selector switch and the manual | Switch to 120/240 V mode with loads disconnected |
| Reading jumps, shows OL or a figure unrelated to 120 or 240 | Meter on the wrong function, range or jack, or a weak battery | Re-check the dial, the leads and the battery on a known outlet | Correct the setup; replace a weak battery |
What each reading at a 240 V receptacle means
The three-reading test turns a confusing number into a diagnosis. Take all three, write them down, and compare them with the patterns below. The chart shows illustrative values for a healthy supply and the two common faults; your numbers will differ by a few volts.
Illustrative nominal values, not measurements. A lost-leg reading can be well below 120 V when large loads backfeed the dead side.
The math behind 208 V is worth knowing because it trips up many people who move between houses and apartments. In a three-phase wye system each hot is about 120 V from neutral, but the phases are 120 degrees apart rather than 180. Two of them combine to 120 × √3 ≈ 208 V. It is the angle between the legs, not a fault, that gives the lower number.
Two numbers to neutral, one between the hots
Work through the steps in this order. The first two clear up most cases in a minute; the rest tell you whether the problem is normal, the appliance, or a supply fault that needs help.
01
Probes
Hot to hot?
02
Meter
Known outlet
03
Each leg
To neutral
04
208 or 240
Building type
05
Escalate
Electrician / utility
1Check where the probes are
On a 240 V receptacle, the two hot slots are the ones that match each other. On a four-prong dryer (NEMA 14-30) or range (NEMA 14-50) receptacle, the two angled or straight blade slots at the sides are the hots, the L-shaped or center slot is neutral, and the round or U-shaped slot is ground. Older three-prong dryer and range receptacles (10-30, 10-50) have two hots and a neutral but no separate ground. A 240 V-only receptacle, like a NEMA 6-series used for some air conditioners and welders, has two hots and a ground and no neutral at all.
With the appliance unplugged, put one probe in each hot slot. If you were previously on a hot and the neutral or ground slot, 120 V was the correct answer to the question you asked the meter. On a hard-wired appliance such as a water heater, don't remove covers to probe terminals; that is electrician territory, because the terminals are live and close together.
2Rule out the meter
Set the meter to AC volts, put the black lead in COM and the red lead in V, and measure a known-good 120 V outlet. You should see something in the 114 to 126 V band. A manual-ranging meter needs a range above 240, such as 600 V or 750 V; on a 200 V range a 240 V input shows an overload indication, not 120. On DC volts, an AC supply reads near zero or bounces around. A meter with its red lead in an amps jack is dangerous across a supply and can blow its fuse, as explained in why a multimeter fuse blows when measuring current.
The point is that setup errors give you obviously odd readings, not a clean, steady 120. A weak battery can skew readings too, covered in why a multimeter shows the wrong voltage. If the meter reads a normal outlet correctly, trust its 120 V reading at the 240 V receptacle and move on.
3Measure each leg to neutral
At a four-wire receptacle, measure from the first hot to neutral, then from the second hot to neutral. On a three-wire 240 V-only receptacle, use the ground slot instead. Both legs should read near 120 V. If one reads near 120 V and the other near zero, one leg is missing upstream of that receptacle. If both read near 120 V but hot to hot reads close to zero, both hots are on the same leg, which is a wiring fault rather than a supply loss.
A missing leg can be local or service-wide. If only this one 240 V circuit is affected, the likely culprit is its double-pole breaker or a connection on that circuit. If roughly half the lights and outlets in the house are also dead, the leg is missing at the main breaker, the meter base or the utility side, which our page on half the house having no power with the breakers looking fine walks through. Odd in-between values on the dead leg, such as 30 or 70 V, usually come from a 240 V load feeding voltage back across from the live leg, or from coupling on a disconnected wire. A meter with a low-impedance (LoZ) mode helps separate that from a real supply; see voltage on a disconnected circuit.
The opposite pattern, where hot to hot is normal but the two legs read unequal values to neutral, such as 100 V and 140 V, points to a failing neutral. Each leg's share of 240 V then depends on how loads are balanced, and equipment on the high side can be damaged. That is urgent; see step 6, and our page on checking for voltage fluctuations at home for the dimming-and-brightening pattern that often goes with it.
4Is it 208, not 120?
If your hot-to-hot reading is close to 208 V rather than 120 V, the building is likely on a three-phase 120/208 V service, common in apartment blocks, condos and commercial units. Nothing is wrong. A water heater or range element rated at 240 V produces less heat on 208 V, because heating power scales with the square of voltage: (208 ÷ 240)² ≈ 0.75, so roughly three-quarters of its rated output. That can explain an appliance that seems slow without any fault at all.
Many appliances list both values on the nameplate (for example, a rating at 240 V and a lower one at 208 V). For EV chargers, the same effect lowers charging power; if that's your concern, our page on slow Level 2 EV charging at home covers the rest.
5Understand the appliance
Many 240 V appliances are really 120/240 V appliances. In a typical electric dryer the drum motor, timer and light run on one leg to neutral, while the heating element sits across both legs. A range works the same way: the clock, oven light and controls often use 120 V, the burners and bake element 240 V. Measuring between a hot and neutral inside such an appliance, or at its terminal block, will show 120 V and be completely correct.
That split also explains the classic symptom pattern of a lost leg: the dryer tumbles but stays cold, the oven light and clock work but nothing heats, or a heat pump's controls power up but the compressor won't run. If an appliance shows that pattern and the receptacle measures about 120 V hot to hot, the appliance is fine and the supply is not. If the receptacle reads a healthy 240 V, the fault is inside the appliance, often a heating element or thermal fuse, and a service technician is the right call for anything that means removing panels.
6Lost leg or neutral: call for help
Once the readings show a missing leg or a floating neutral, stop measuring and get the right people involved. A homeowner can safely do three things: switch off large 240 V loads so they don't backfeed or overheat, check whether a double-pole breaker has tripped (switch it fully off, then on), and note which circuits are dead. If the breaker trips again, or resetting doesn't restore the missing leg, stop there.
Call the utility first if half the house is out, the neighbors have similar problems, or lights brighten and dim; they are responsible for the transformer and the service drop and often check them without charge. Call a licensed electrician for a failed breaker, burnt bus stab, loose lug or wiring fault inside the house. Never open the panel or the meter base yourself. A breaker that keeps tripping once restored is a different problem, covered in why a circuit breaker keeps tripping, and a panel that hums or buzzes is covered in why a breaker panel buzzes.
Meters suited to 240 V checks
Household 240 V receptacles sit in CAT III territory, so pick a meter and leads rated at least CAT III 600V. LoZ mode is useful for separating backfed or coupled voltage on a dead leg from a real supply. These come from our verified multimeter list.
Multimeters for 120/240 V household checks
CAT III 600V, True RMS, LoZ for ghost voltage and built-in VoltAlert non-contact detection. Hands-on Tested.
CAT IV 600V / CAT III 1000V, True RMS and LoZ at a budget price.
CAT IV 600V / CAT III 1000V, True RMS and an analog bar graph. No LoZ. Hands-on Tested.
As an Amazon Associate I earn from qualifying purchases. Prices and availability are shown on Amazon.
Frequently asked questions
Why do I get 120 volts from a 240 volt outlet to ground?
Because each hot terminal of a 240 V outlet is one leg of the split-phase supply, and each leg sits about 120 V away from ground and neutral. That reading is normal and expected. The 240 V only appears when you measure between the two hot terminals. Measuring each hot to ground is still a useful check, since both should read close to 120 V.
Is 120 volts on each leg the same as 240 volts?
On a split-phase service, yes, provided the two legs come from opposite ends of the transformer winding. Their voltages are opposite in polarity at every instant, so measured end to end they add to about 240 V. If both of your measured hots came from the same leg, they would be in step and you would read roughly zero between them instead.
What does it mean if hot to hot reads 0 volts?
A near-zero hot-to-hot reading with both hots at about 120 V to neutral means both conductors are fed from the same leg. That can happen when a 240 V circuit is wired to two single-pole breakers that land on the same bus, in some tandem breaker arrangements, or on a generator switched to 120 V only. A licensed electrician should correct it.
Can a bad double-pole breaker give 120 volts instead of 240?
Yes. A double-pole breaker has one contact for each leg. If one contact fails or its bus connection is burnt, one hot still reads about 120 V to neutral while the other reads near zero, and hot to hot falls to around 120 V or less. Replacing a breaker means working inside a live panel, so leave it to an electrician.
Why does my dryer run but not heat?
In many electric dryers the motor, timer and light run on 120 V between one hot and neutral, while the heating element needs the full 240 V across both hots. If one leg is missing, the drum can turn while the element stays cold. Measure the receptacle with the dryer unplugged; if hot to hot reads about 120 V, the supply is at fault, not the dryer.
My apartment reads 208 volts, not 240. Is something wrong?
Probably not. Many apartment buildings and commercial spaces are fed from a three-phase 120/208 V system. Each hot is still about 120 V to neutral, but two hots are 120 degrees apart rather than 180, so they combine to about 208 V. Appliances sold for those buildings are rated for 208 V or 208/240 V. Check the appliance's nameplate.
Where to go next
Why Does Half My House Have No Power? →
What to do when a whole service leg is missing.
How to Check for Voltage Fluctuations at Home →
Readings that wander up and down, and what they point to.
Voltage on a Disconnected Circuit? →
Ghost voltage and why LoZ mode helps tell it apart.
Best Multimeter for Electricians →
Meters with the CAT ratings that suit 240 V work.
