Best non-contact voltage testers

How to choose

Treat the pen as a first check only

A non-contact pen senses the field around a live wire without touching metal. It's a fast way to learn that something is on, including before you open a box. It can't tell you that something is off. Fluke's sheet says not to rely on its tester for safety and calls this type of detector unsuitable for deciding whether a circuit is hazardous. Klein's manual says voltage could still be present with no indication.^{3 4} Fluke's sheet is also addressed to competent persons and says users should be trained in the risks of measuring voltage.³ Berkeley Lab doesn't authorize these pens for proving that a circuit has no voltage.¹³

So if you'll touch conductors, buy a multimeter or a two-pole tester, which reads through two probes that touch the circuit. Turn off the breaker, then confirm the power is off with that tool before you put a hand on anything.^{3 14} Household voltage can kill. In a 1986 federal case report, an electrician's helper died on a 110-volt circuit after choosing not to use a circuit tester.¹⁵

Check every new pen at your own outlets

Outlets are where pens most often missed live voltage in the small tests available. Beyond the Fluke results above, the NCVT-1P stayed green in one video until it was pushed hard into a hot slot.¹⁰ Klein warns that socket design can affect its testers.⁶

The fix is simple. Try the pen on a known live outlet of each type in your house while you can still return it. If it can't read them, send it back.

Insist on a clear sign that it's on

A pen with a dead battery and a circuit with no power look the same if the pen gives no sign of being on. Skip any pen without a plain indicator. Both Klein and Fluke tell you not to use the tester when that sign is missing.^{3 4} The flash or light shows only that the battery and circuit are working. It doesn't replace a check on a known live outlet before and after you use it.

Pay for low voltage only if you'll use it

Every pick covers 120 and 240 volt household circuits. You only need a 12 volt floor for doorbells, thermostats and similar wiring.^{3 6 8} Klein's manuals say its pens won't read DC, and Fluke's range is AC only, so none of them will help with DC circuits.^{3 4 6}

Don't choose by safety rating

A CAT rating describes how well the tool stands up to the electrical system it's used on. It says nothing about how well the pen senses voltage. The Fluke 1AC II, the Klein NCVT-1P and the NCVT-3P are all listed as CAT IV 1000 V, so the rating doesn't separate them.^{3 4 6} It's still worth avoiding a pen with no rating at all, and a master electrician quoted by Bob Vila says a tester for home use needs a rating up to 250 volts AC.⁸

Prefer a false alarm to a miss

Very sensitive pens sometimes alert when nothing is live, and Bob Vila's reviewer marked one down for it.⁸ For a homeowner that's the better way to be wrong. A false alarm costs you a minute with a meter, while a missed live wire can shock you.

Use it the same way every time

Check the pen on a known live circuit, test the circuit you shut off, then check the pen on the known live circuit again. Both makers ask for this, and electricians call it live-dead-live.^{3 4 14} OSHA requires workers to verify with test equipment that parts are off before treating them as dead.¹⁶

Press and release the power button fully. Don't trust the pen on shielded cable or wire in grounded metal conduit, and don't assume a neutral or ground is dead. A glove or other insulation between your hand and the pen can stop it from reading.^{3 4 17} Keep the pen out of damp or wet places, and don't put it on bare live metal. Klein's manual says not to apply it to uninsulated hazardous live conductors.^{3 6} Fluke says to take the batteries out when the tool will sit unused for a long time, so a pen from a drawer needs a fresh check.³

How many you need

One pen per household is enough, plus a contact tester if you'll work on wiring yourself. If you'll never touch wiring and always hire an electrician, you can skip it.