What We Cover in this Article:

  • Why Higher Voltage Can Use a Smaller Wire
  • Why Do We Want a Smaller Wire Size?
  • Why Does Wire Size Matter for Current?
  • Why Lower Voltage is Safer to Work On for Humans 🙂
  • Why Use 240V for Ovens But Everything Else is 120V?

Why Higher Voltage Can Use a Smaller Wire:

The short answer is the higher the voltage, the smaller the current, which means the smaller the wire size can be.

Buying electrical wires can be expensive when you have to jump to the next conductor size, but it’s not always just about wire size, depending the use-case!

We electricians use TRANSFORMERS to manipulate voltage and current inversely.. it’s actually amazing technology!

Electrical Transformer High Voltage Flex Connection
Here is a picture of a transformer from a jobsite. A transformer can be used to reduce or increase voltage.

In other words, if you have too many amps, you can use a transformer to crank up the voltage, which reduces the amps. Since amps make a wire hot, this is a way to keep wires small! Also due to the increased voltage after a transformer, it allows electricity to travel to its destination with minimal loses on electrical lines, like traveling along VERY LONG electrical distribution lines!

One additional trick electricians use to reduce wire size is something called phase. Most homes are “single-phase”, and only have two hots (A and B phase). Commercial buildings, and most power lines, are “three-phase” allowing for an additional reduction in wire size, in addition to this “transformer” technology.


Why Do We Want a Smaller Wire Size?

A smaller wire size allows the purchase cost to be less, and it’s much easier to install and maintain!

Sometimes when electricians work on a building, the odd time you are dealt with a big task of working with some big wires. At these times, you just have to prepare for it and plan your attack. Usually these bigger wires are installed into the MAIN DISTRIBUTION.

Electrical Main Wire Feeds in Underground Pipes from Transformer Outside to Power the Building
These were the main wire feeds to the building. The wire size can also be reduced by using “parallel feeds”, meaning you can pull multiple sets of wires of the same phase to reduce the wire size, compared to just a single set of wires (a set of wires is how many phases are required.. A, B, C in a three-phase electrical system).

But, if this wire is outside, like on power lines, using these HUGE wires can be dangerous, and would require A LOT of money and strength to hold up.

Think about your power lines. What happens if a BIG storm came? If we used HUGE wires, the power line supports would have to be MASSIVE in strength! (And probably more supports would be needed to prevent wire sag!)

Transformer mounted on top of power pole to provide power to residencies
Here’s an example of powerlines with a transformer mounted near the top. (This allows the wire size on power lines to be smaller, but then power a small number of homes with safer voltage).

So that’s why transformers are used to CRANK up voltage.. sometimes upwards to 50,000 or even 100,000 Volts, which can reduce current, and give us a MUCH smaller wire size!!

Imagine trying to distribute power on only 120V? The cost of infrastructure, and the wire size cost alone would probably put most municipalities out of business lol!


Why Does Wire Size Matter for Current?

When electricians go to school, they are taught what is the MINIMUM wire size that can be pulled to a device (a plug, light, or maybe a heavy duty heater that requires A LOT of power).

You see, CURRENT (amps) makes a wire HOT. A wire is only rated for a certain amount of amps until you MUST go to the next wire size by electrical code.

For example.. if #14 AWG Copper is rated for 15 Amps, but you need 40 Amps to power your oven, you’re going to risk a fire if you put #14 under a bigger circuit breaker. (Don’t do that!)

Electricians have code books which have charts telling them what wire size is capable of how much current (amps) it can handle.. and there is a difference between SOLID and STRANDED conductors when it comes to how many amps they can handle.. so keep that in mind!

So the whole goal here is to always protect the wire… we do that by making sure we have properly sized our electrical conductors (wires) for the rated load (if your electrical device needs 30 Amps, make sure your wire can handle 30 Amps, minimum.. making sure there aren’t additional code rules telling you to upsize your wire!)


Why Lower Voltage is Safer to Work On for Humans:

As mentioned, if power is being distributed to cities at let’s say 50,000 Volts.. there’s no way anyone would want to work on that kind of electrical potential (voltage).

There’s WAY too much risk for arcing, electrocution and death. But.. some people do work on power lines LIVE at these high voltages, because power cannot shut off for some of these cities.. don’t believe me? Watch this!!!:

Obviously only someone who truly knows what they’re doing would even consider this!!!! Thank-you for your amazing work for the people! .. oh sorry, he mentioned, 500,000 Volts (Half a million volts, yes!)

Alright, yeah intense! But, now I’ll break down how electricity gets brought down to a safer voltage for electricians and normal citizens, and how we use electricity, and work on electricity, on a daily basis.

Voltage gets CRANKED up to very high voltages to reduce current on these power distribution lines, which REDUCES the wire size. But once the voltage gets closer to town (around more people, vehicles, etc.), they will then send these wires into an electrical substation (electrical transformer station).

Electrical Substation to Reduce Voltage and Power the Neighborhood
This is an example of an electrical substation where very dangerous amounts of voltage are. Since these electrical transformer substations are very important to a city’s power, they are quite big, and have warning signs and fences to keep out!

This transformer station will take that let’s say 50,000 Volts, and may be reduced it to 13,000~ Volts due to safety.

The voltage still must be quite high to reduce wire size, as a lot of homes and business need power still.

Then FINALLY, before it enters your home, or commercial building, there is usually one final transformer usually right outside of certain homes on a street block, or beside a commercial building.

This final transformer may power many homes, or many businesses! Transformers are super versatile, seriously!

Typical Transformer for Underground Pipes on a Residential Street Block
This is a typical transformer you’d see on a residential street block. This transformer would only power a couple homes, before another transformer is needed to reduce voltage for other homes. A transformer can only handle so much current (heat), and homes may get too far from the transformer, too.

Anyways, this final transformer before entering your home would reduce the voltage to something like 120V or 240V in North America. The wire size to your home may even be bigger than the wires FEEDING the the Transformer!!!

This is all because transformers are an absolutely amazing invention….

Remember, when talking about wire size, we are focused on AMPS, not volts! AMPS is what produces heat, and it’s important your wire size can handle the amount of amperage that you’re electrical load requires!


Why Use 240V for Ovens But Everything Else is 120V?

To summarize, in North America, we use 120V with a neutral for our electrical devices (one hot and a neutral [white wire]).

This is fine for basic devices like lights, a computer, and TV’s as they usually draw less than 2-3 Amps, which allows you to connect many devices to one 15 Amp circuit at once!

However, some equipment, like an oven or stove, still requires A LOT of power in your home.

You see, 120V only has 1 hot wire (and a white neutral).

240V actually has two hot wires (and there is often a white neutral wire included because an oven also has lights and electronics that require 120V, still…)

So if you read closely, you’ll remember if we increase voltage, we can REDUCE current (amps), making the wire size smaller.

I’ll give you a real-world example here:

These electric cook top ovens (if not using a gas range) can consume A LOT of power. For example, we electricians by code (make sure to check your local codes!) have to pull a #8/3 AWG copper wire to an oven in your home. It uses 2 Hot wires (Red + Black), and also has a Neutral (for electronics and the light inside the stove).. and of course it has your bond wire for safety!

(Wires that are insulated are counted as conductors when buying wire.. such as 14/2.. it has a black, a white, and a BARE bond wire).

Imagine you’re cooking a big meal, and end up using all cook top burners AND the oven at the same time.

After a quick search on Home Depot, let’s say the average oven is around 8,500W (BASIC OVEN)..

Let’s try 120V first 🙂.. (Because an oven is 240 Volts.. they’re still using that same higher voltage means smaller wire trick!!!)

8500W / 120V = 70.83 Amps!

So now let’s treat it as if in a normal residential home in North America.. (if in commercial, make sure to follow your electrical spec sheet)

Electric ovens are 240V, let’s try that again…

8500W / 240V = 35.42 Amps!!!!!

Yeah, that’s crazy, isn’t it?

If you were to look at the cost and size of wire for 70 Amps, versus the cost and wire size for 35 Amps.. you’d be shocked.. and not to mention the wire size holes you’d have to drill!

The people who invented this stuff truly were smart people. I’m just repeating what I’ve learned over the years…

The idea of using 240V in these situations is very smart and cost effective. Plus, the plug is behind the oven where no one could reach unless you pull out the oven to do maintenance or clean makes it quite safe, whereas normal plugs are just 120V.


Wrapping Up About Why We Use Higher Voltages in Electricity:

In short, we use transformers to switch between high and low voltage to allow for smaller wire sizes. Within transformers, if we increase voltage, it decreases current (inversely proportional).

The one thing that doesn’t change is the VA on a transformer (kind of like watts).

Sometimes equipment requires odd voltage numbers like 480V, or 277V, so transformers can also be used in those situations, too. But most often, transformers are used to keep the amps low on a wire, to reduce wire size.

If you can imagine how much power a city can use (maybe 50,000 Amps), how big of a wire do you think you’d need to power that?

Three phase power lines with a transformer in residential area
You can see the many power lines and poles required to support a system like this. It’s important wire size is not too big to preserve the life of the power poles, and keep things relatively safe. (Ideally, underground installation is more suitable, but power poles were older technology, and must be maintained to provide power to the many homes).

If we then tremendously increase voltage to 100,000 Volts, it quickly drops the number of amps that a much smaller wire can handle. This makes it more affordable to manufacture, install, as well as maintain.

Now once the power hits a normal residential or commercial building, we operate at much safer voltages for electricians and non-electrical people to use power by plugging in their devices.

It reduces the risk of extreme dangers of electricity (which you can still get very hurt at 120V), but imagine having to work on a 10,000 Volt plug 😎.. (you’d probably need sunglasses! lol)

So with that perspective, 120V is definitely safer, but there’s always a chance of severe injury with electricity. That is why you should never work on live power, as accidents happen quick.. even when you know what you’re doing.

Does that make sense?

It’s all about protecting the wire from overheating. But in this case, it’s also about using a smaller wire size to power the world, and make it easier to install and manufacture..

So there you go.. that’s why there’s high voltage and low voltage.

Also a fun fact.. In Canada high voltage is over 750V! Which means in our homes we work with “low-voltage”.. And communication stuff like ethernet and coaxial cable is “extra-low-voltage”.