a voltage tester connected to a residential breaker box


Originally contributed by Jeff Butler • last updated 2/18/2021

It’s not everyday that most of us will be required to understand electrical terms, such as voltage, but having a basic grasp of how electricity works can not only help prevent damage to your appliances and devices, it can also help you identify and fix problems on your own.


When talking about your home’s electrical system, the term voltage refers to the amount of pressure that pushes the electric power from the breaker box through a house’s electric circuits to any connected fixtures, appliances, or plugged in devices. In a more technical sense, voltage (often referred to as the potential difference) is the electromotive force that’s needed to move a unit of electric charge through an electric circuit. By comparison, if an electric current were thought of as a river, the term voltage would be similar to the force carrying the water downstream. Testing the voltage in your home’s electric circuits is often done (typically by a professional) using a non-contact voltage tester.

What Is Voltage Drop?

If you’ve ever plugged in a device to an outlet and suddenly had flickering lights or dim lights, you’ve probably experienced voltage drop. Voltage drop may seem harmless but it can be a serious concern and the cause should be identified and fixed immediately:

  • If an electric circuit has too much electrical load on it (i.e. too many devices drawing power at the same time), there is potential for voltage drop to occur, which could result in lights dimming, devices overheating, and increased electrical consumption.
  • In some cases, voltage drop may be the result of a bad connection somewhere along the circuit. Improperly wired or loose connections on electrical outlets and fixtures can not only cause voltage drop but are often the source of electrical fires and should be fixed immediately.
  • In certain cases, a professional may need to fix the problem by upgrading your home's conductors. The proper wire size for an electric circuit is often determined using a voltage calculator.