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How to Test an Electrical Outlet (Step-by-Step Photo Instructions)

Collage photo of electrical outlet testing.

This is an expertise level article written and provided by the folks at Thanks guys!

It’s important to make sure the electrical wiring in your house is done properly and that your outlets work like they should. Malfunctioning outlets or bad wiring can cause any number of safety issues.

Bad wiring can also damage sensitive electronics, (there’s no worse feeling than seeing your new dishwasher broken due to faulty wiring), and dead outlets are at the very least a nuisance.

Thankfully, there is an easy way to test your outlets to make sure they work, are grounded properly, and the polarization is as it should be. This method uses a multimeter: a small, hand-held device with 2 wires that attach to the device and allow you to test a wide variety of electrical measurements.

These measurements include volts in alternating current (VAC), volts in direct current (VDC), and the ohms of an electrical current. When it comes to testing household electricity you will only need to test the alternating current (AC).

Though this method is fairly simple and straight forward, it does involve work with live electricity, so let’s take a look at a few safety tips before we get to the steps involved in using a multimeter:

Safety Tips

Usually, when you work with electricity, you want to make sure the power is turned off to avoid any potential for electric shock. When you are testing to see how power flows through an outlet, though, you will need to leave the electricity on to get a reading.

This means it’s important to work slowly and be mindful of everything you are doing while going through the process so you don’t accidentally cross wires or get a nasty shock. There are also some extra precautions that should be taken before you start:

  • Wear rubber-soled shoes
  • Don’t touch any conductive surfaces (metal, copper, etc.)
  • Check your equipment for loose wires or cracked handles
  • Always hold tools by insulated rubber handles or grips
  • Never let the multimeter probes touch
  • Never touch the multimeter probes yourself

How to Test Your Outlet

1. Connect the leads

Your multimeter will come with 2 wires with metal probes at the end. These are what will allow you to test your socket and will need to be attached to the multimeter. The red wire will need to be connected to the “volts” input.

This will often be marked with a red circle, plus sign, or the Greek letter omega (which looks like an upside-down horse shoe). The black wire should be connected to the “com” input which will be marked with a black circle or a minus sign.


Inserting prongs of multimeter into outlet for testing the electrical outlet

2. Choose the right setting

You’ll need to set your multimeter to read alternating currents. This is often done with a dial or maybe a switch depending on the model you are using. The AC setting should be labeled AC, VAC, or Volts. Most multimeters these day will come with automatic range detection, but if yours does not you should set it to a range with a minimum of 100 volts.

3. Place the leads into the sockets

Keep in mind that the power is still on while you do this; it’s important that the wires are placed into the correct slots in the correct order and don’t touch at any point. You’ll need to start by placed the red lead into the narrow slot on the right. This is the slot that should carry the voltage.

Then place the black lead into the wider slot on the left. This should be the ground or negative.

Testing electrical outlet with multimeter leads


4. Check the reading

Household alternating currents in America should run between 110 and 120 volts. If your socket is working right, a number in this range will be displayed on the screen.

If there is a negative sign in front of your reading, this means the polarity has been reversed. This is usually not a problem for minor household appliances, but can damage more sensitive equipment. If you plan on plugging complicated or expensive equipment into that outlet, you may want to get an electrician to fix the polarization first.

If there is no reading, you can try moving the black lead from the left-hand slot to the wider slot in the middle (on a 3-pronged outlet). If there is still no reading then your outlet isn’t getting power.

Getting a multimeter reading when testing an electrical outlet


 5. Remove the leads

It’s important to remove the leads in the opposite order that you placed them into the socket. This means you should take out the black lead first, followed by the red one.

6. A final test

One more test you may want to do is to make sure your outlet is getting live power through the correct side of the socket. To do this, place the red lead in the socket on the middle of a 3-pronged outlet and place the black lead in the negative or ground socket on the left hand side. There should be no reading, or the reading should be zero.

If there is a reading, this means someone wired your socket incorrectly and you will definitely need to fix that before using the socket. Be sure to remove the wires in the correct order again after this test, so black first, then red.

What’s Next?

If your outlet isn’t working correctly, there’s no need to panic. Most electricity issues can be easily fixed on your own, even if nothing came up during your initial home inspection. A dead socket will need to be completely replaced – new ones can usually be bought for around a dollar.

If your socket is wired incorrectly this can be fixed as well by simple removing the outlet and switching the connection points for the wires. The good news is that this kind of electrical work can and must be done with the electricity off.

So if you can read the currents in your outlet with live electricity, replacing it with the electricity off should be a breeze! Just be sure to look up detailed instructions ahead of time and always make safety the first priority!