Nominal Voltage

What is Nominal Voltage?

Nominal voltage is the stated voltage at which a device is safe to operate without damage to the system. The nominal voltage may vary from the actual voltage in a system and is often printed with additional information on the tolerances allowed without danger to the system.

Key Takeaways:

  • Nominal voltage is the stated voltage at which a device performs best at without danger to the system.
  • The nominal voltage may not be the actual voltage at which a system operates.
  • Often, nominal voltage is expressed with additional information about the tolerance for safe variances from nominal.

Understanding Nominal Voltage

Nominal voltage refers to the named or maximum voltage at which a specific circuit or system is designed to operate without damaging the equipment, such as a battery or solar array. Nominal voltage may, and often does, vary from the actual voltage that a system operates at. For instance, a 240-volt system may in actuality operate between 216 and 253 volts. It is simply a convenient way to refer to a voltage class without needing to be precise. Nominal voltage is sometimes referred to as nominal voltage rating or rated voltage.

Often, the nominal voltage of a system is expressed as two numbers in a fraction, such as 115/230, where the lower number is for smaller devices and the larger number is for large appliances. Since most electrical appliances are designed to work with a specific voltage or waveform shape, correctly matching an appliance with its nominal voltage can be a critical matter for safety.

If AC or DC precedes a number, then this is the nominal voltage for that device. For example, a device that has AC 230V would have the nominal voltage of 230 volts on an AC system. Sometimes this information will also have additional percentages that indicate the tolerance that the device has for variances. A device that has DC 12V ±25% has a nominal voltage of 12 volts on a DC system with a tolerance of plus or minus 25%. If the terms Vdc or Vac follow the number then there is no additional tolerance allowed.

Related Terms

AC – AC, or Alternating Current, is a form of electric current that is commonly used to power homes and has a signature sine-wave shaped current.

DC – Direct current, or DC, is a type of power current used by many small appliances and off-grid applications.

Voltage – One type of measurement used in electrical systems that denotes the force needed to move an electrical current through a system.