Electrical Voltage Explained - What Is It and How Does It Work ?

August 24, 2016 3 Comments

voltage and current

For electrical beginners, understanding the differences between voltages is a common issue, and sometimes can be a very confusing task that can lead to endless debates.

Which one is better? 24-volt or 12-volt? Which one is safer between 120-volt and 240-volt? What do all those numbers even mean ?

In this article, we will discuss the differences between all the common voltages used in both DC and AC applications, and the advantages as well as disadvantages of each.

Before we begin, let's first understand the basics of electrical voltage.

Basics of Voltage


To understand the fundamentals of electrical voltage better, let's imagine that our wire is a water pipe, and the electrical current is the water current.

What then, is the electrical voltage in this water pipe assumptions? It is the water pressure inside the pipe. In fact, voltage is also often called electrical pressure or electrical tension. Check out this history of the term 'voltage' by Think For Yourself.

If we remember our junior high physics, pressure affects the speed of the water current entering the pipe. The harder the pressure, the slower the water speed, and the less water entering per any given time.

Understanding that basic principle, the higher the voltage, the less current will be entering the wire per any given time to achieve a certain power.

Thus, we came into the famous equation:

    P=V times I

Where P is power, measured in Watts, kiloWatts, or megaWatts, I is the electric current measured in ampere, and V is voltage.

So, resuming our analogy of water, what changes as the voltage change?

In water, the higher the pressure, the more harmful it is to the human body. Is that the case with voltage? Apparently, yes, the higher the voltage, the more dangerous it will become when electrocution occurs.

In DC voltage applications, 12-volt and 24-volt are the one commonly used. 48-volt is a bit less common but is still widely applied in today's DC voltage applications.

On the other hand, in AC applications (the electricity supplied by the power company), 120-volt is the standard in U.S. and North America, while 240-volt is the standard for almost the rest of the world.

So, is the U.S. electricity safer than the rest of the world? And is 12-volt safer than 24-volt? The answer is a bit more complicated than that, so let's dig deeper.

Effects of Voltage Differences

We have discussed how generally lower voltage is safer during electrocution (safer doesn't mean entirely safe, reader's discretion is advised.) What other effects will a higher, or lower voltage bring to our electrical system as a whole?

Here are some notable ones:

  • Wire Size: As discussed, the lower the voltage, the more currents will be needed to power up an appliance or a light bulb. As electrical current generates heat, this will mean that you will need a thicker wire that can withstand that heat. In short, the cost for your wirings will be significantly higher.
  • Efficiency: Conductors (the metal inside your wires that conducts electricity) generally is more efficient when operating at higher voltage. Higher voltage= save more money in the long run.

So, in general, a higher voltage is more economical, while lower voltage is safer. However, these differences can extend differently within DC and AC applications, so let's divide the discussion into each of them. Let's start with DC first.

DC Voltage: 12-Volt VS 24-Volt

Although in DC applications more voltage rating are available, such as 48-volt, the principles should apply in a similar way. Thus, we will use 12-Volt and 24-Volt as the focus of the discussion.

The differences we will find between the two are:

  • Safety: Although in theory 12-volt will be safer, the differences will be minuscule since both are of relatively low voltage rating. Safety won't be an issue for these DC systems.
  • Voltage Drop/Efficiency: As mentioned, the lower voltage will cause more losses, so in general you will find more voltage drops in a 12-volt system.
  • Wire Gauge: As discussed, a 12-volt system will require thicker cables, which will be a more expensive investment.
  • Appliance/Lighting Product: Generally a higher voltage DC appliances will cost more. As a comparison, you can take a look at our 12V and 24V LED lighting catalog here. However, as you can see, nowadays lighting and appliances available for both 12V and 24V are common, so it won't be much of an issue.

In conclusion, a 24-Volt system will generally need more initial investment upfront, but will save more money in the long run.

Check out this video by DIY one for allfor a more thorough discussion about these two systems.

Moving on to the AC applications, what is it that made the U.S. use a different voltage than the rest of the world?

AC Voltage: 120-Volt VS 240-Volt


Can we take the same conclusion that 240-volt will be cheaper in the long run while 120-volt is safer? Well, yes and no. Let's delve further into that question.

North America's 120-Volt is actually a 240-Volt voltage divided into two. How did that happen? In our previous article about the history of the light bulbs, we have discussed that Thomas Alfa Edison was responsible for electrical distribution in the U.S., and he is certainly responsible for the 120-Volt choice.

Some claims that it might be that Edison's early light bulbs only work with 120-Volt voltage, but most Americans will say that the 120-Volt choice is because of the reason of safety. Check out this article fromWorld's Standards for further history lesson.

So, the basic principles we found on our previous discussion are still intact:

  • 120-Volt electricity is generally safer during an electrocution.
  • Thicker wire gauge is needed for the 120-volt system, this is why we have American Wire Gauge (AWG).
  • Efficiency is generally better in the 240-volt system. But, because as mentioned, the 120-Volt system is actually a 240-Volt system divided into two, the effect and voltage drop won't be as significant as 24-Volt vs 12-Volt.
  • For lighting and appliance issue, it has more or less equalized

However, 120-Volt and 240-Volt is not a matter of choice, but rather the matter of where you live in. Problems may arise, however, when you are traveling to a country with different voltage rating than yours. What should you do with your devices and appliances then?

Using Different Voltages

There are a few considerations you should make when you are traveling to different country, or when using a DC application with AC voltage:

  • Always check the voltage rating of your device/appliance/light bulb. Most modern appliances are manufactured to be able to operate with 100V-240 V of voltage. However, some still require an exact voltage rating.
  • Under-voltage, the case when a device is operating below its voltage rating, can cause the appliance to be not working at all, or working below its optimal level. For example, when you charge a cellphone with a voltage below its standard, it will charge very slowly.
  • Over-voltage, on the other hand, is more dangerous and can damage your appliances permanently.
  •  For a device that requires an exact voltage level, for example, a 12V LED strip, u will need to use an adapter. Usually, the adapter is included with the appliance. However, this can also be a complication when you have a 120V to 12V adapter and you are traveling to a 240V country. You will need a new adapter then.


Now that we understand voltage differences and associated effects, we can be more careful when traveling to another country, or deciding which voltage to use in our DC off grid system.

Nowadays, many appliances and lighting are manufactured to be able to operate in different voltages, certainly made life easier for us. However, make sure to check each of your device's voltage rating especially when traveling to other countries.

3 Responses

Software Criticizer
Software Criticizer

June 29, 2022

Absolutely unreal the ignorance of 90% of the world’s population. People making-up random reasons why 240v AC common distribution in a household is “safer” than 120v AC common distribution (not talking about A/C units). By their logic we should all be using 480v distribution in homes. WOW. Yes 120v AC is generally 10 times safer logarithmically than 240v AC and 60v AC consumer distribution would be 10 times safer than 120v AC. On the other hand, 480v AC distribution in homes would be 100 times more dangerous than 120v AC. It is an UNEDUCATED dumb population out there.

Deepak Narain
Deepak Narain

January 18, 2022

my question is an applince where input is 240 volts and output is 12 volts (bulb) works fine
will it work fine in US where input is 120 V but output is 12 V ?
Please advice

Jesse Anderson
Jesse Anderson

January 18, 2022

thank you !!

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