What is VAC in Electrical?

Do you want to know what the acronym VAC is/means in electrical terms? I am a certified electrician, and I expand on this in a short article below.

You might see the marking 110 VAC or 120 VAC in most electronics.

Generally, VAC is just a term used in electrical for volts AC. You are probably familiar with the volts DC; it represents the direct current voltage. And the same way, VAC represents alternating current voltage. The only thing you should know is both VDC and VAC represent voltages.

Continue reading for a more in-depth explanation.

Everything You Need to Know about VAC

Lots of states in North America use 110 VAC or 120 VAC. And you might spot these markings on some electronics, such as computers, current transformers, and digital multimeters. But do you know the meaning of it?

VAC is a term used to represent alternating current volts. So, there is no such thing as VAC power. It’s just the voltage of the alternating current circuit.

However, to understand this properly, you should understand the difference between VAC and VDC.

What are VDC and VAC?

First, you should know about DC and AC to understand these two terms.

Direct Current (DC)

DC power flows from the negative to the positive end. This flow is one-directional, and a car battery is one of the prime examples.

Alternating Current (AC)

Unlike DC power, AC power flows on both sides. For instance, in any given second, AC power travels from negative to positive and positive to negative. The main power supply that comes to your house is the best example of AC power.


If you understand AC and DC power clearly, there is nothing to understand about the VDC and VAC.

Here is a simple explanation.

VDC represents the DC volts value, and VAC represents the AC volts value. If you take a digital multimeter and closely inspect it, you can see both of these markings. However, if you want to use these settings in a multimeter, you should know which circuits deal with VDC and which deal with VAC.

Where Can I Find VAC?

Most parts of North America use 110 or 120 VAC for common households. You can locate this marking on alternating current devices. However, when it comes to Europe, they use 220 VAC or 240 VAC. 

Quick Tip: 120 VAC power alternates from 170V to zero. Then, again it rises to 170V. For instance, alternating current cycles 60 times in one second. That is why most AC power has a frequency of 60Hz.

RMS Voltage of 120 VAC

In truth, 120 VAC alternates up to 170V and goes down to zero. This sine wave is equal to 120 DC volts and is known as the RMS value.

How to Calculate RMS Value?

Here’s the formula for calculating the RMS value.


The peak voltage is 170V.


VRMS = 170*1/√2

VRMS = 120.21V

Why Do We Use VAC?

You’ll lose some part of energy whenever you try to change energy from one form to another. Hence, to minimize this energy loss, generators produce electricity at high voltage and transmit it in AC form.

However, common households don’t need electricity with high voltage. Because of that, this AC electricity goes through a step-down transformer and gives lower voltage for home use.

Important: Most electronic devices don’t operate with AC power. Instead, they use low-voltage DC power. Therefore, lower-voltage AC power is converted into low-voltage DC power with the help of a bridge rectifier.

Take a look at some of our related articles below.

Video References

Kuya JTechnology

Ron Nelson’s Place

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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