What Size Wire For 15 Amps? Your Complete Guide

Do you need to know what size wire for 15 amps? Maybe the time has come to replace the wire and you aren’t sure what size you need?

Or is this your first time using wires and aren’t sure where to start?

No matter the reason that brought you here, we have the answers for you!

Finding out what size wire for 15 amps can be tricky, especially if you have never done it before.

You head online for some guidance but are met with pages and pages of conflicting and contradicting information.

Frustrated and confused, you are left unsure where to turn or who to trust. And your 15 amp remains wireless, what are you supposed to do?

What Size Wire For 15 Amps Your CompleteGuide

Well, you can turn to us! Today, we are here with all the answers that you need!

Keep reading to find out what size wire for 15 amps and everything else you need to know about them!

What Is An Amp?

Before we dive into today’s article, let’s have a brief recap for those that need it.

An amp is the rate of flow of electricity through a conductor when the difference between its ends is one volt.

An amp measures how much electric charge flows past a point in an electric circuit each second.

You will see the unit of measurement mentioned throughout the article today and in relation to all things circuits!

What Size Wire Do I Need For 15 Amps?

Let’s dive straight into knowing what size wire for 15 amps! To use a current of 15 amps, you need a wire with a 14 gauge.

You can also use a 12 gauge wire, which can sometimes be the safer choice. However, a 14-gauge wire works just as well!

There are several types of wires, making it tricky to know which one should be used.

We recommend checking your breaker box to see what size wires run from your house’s main panel or the service panel.

If these wires are 12 gauge, you can go with an extension cord for 15 amps. If not, you will need to find out how many amps the circuit uses.

You might also need to purchase a larger wire to use with your circuits.

Sometimes, a 15 amp will be used with a 20 amp circuit. When this happens, the 20 amp circuit will carry the 15 amps safely.

The remaining 5 amps are not safely carried. You need to consider the extra power dissipation in the line before installing the wire. Will there be any safety risks?

The last thing you want to do is cause a power cut or pose a safety risk to your home!

15 Amp Vs. 20 Amp

Let’s take a closer look at 15 amps and 20 amps now. Most circuits in residential homes use 15 amps, running on 15 amp breakers.

As we mentioned earlier, you can run a 20 amp (see also: What Can You Run On 30 Amps In An RV?)circuit if you have the correct wire size.

20 amps generate double the heat of a 15 amp circuit and tend to have thicker cables for longer runs.

This means it is not often safe to use 20 amps unless the cable is three times the size of one typically used for a 15 amp circuit. This translates to 3/0 AWG (more on AWG below).

Larger wires tend to have a bigger price tag, so be sure to consider whether it is worth spending the extra money.

Sure it will save some time when you install them, but is that worth spending more, especially if you are on a tight budget?

As we mentioned earlier, 15 amp circuits need a 14 AWG wire and 20 amp circuits need a 12 AWG wire.

If you are ever unsure, you can check with your local building code to see what the minimum gauge wire you can use is.

Be sure to remember that a 20 amp breaker on a 14 AWG cable or smaller can cause problems, with the possibility of an electrical fire!

What Is AWG (Gauge)?

What Size Wire For 15 Amps

We have mentioned gauge and AWG throughout the article, but what does it mean? It refers to the thickness of an electrical cable.

The larger the gauge number is, the thinner the wire is. The thinness of the wire makes it lighter and more flexible.

The downside is that it can limit how much power can pass through at any time. Smaller cables will have thinner wires internally that handle less amperage than thicker wires.

Wires with larger numbers will be thinner than wires with lower numbers.

For example, a 10 AWG wire is larger than a 12 AWG wire. Want to know more about the range for gauges?

Check out our brief list below.

  • 20 – 16 – used in cars and similar machines where fuses or battery cables carry a lot of content.
  • 14 – 12 – typically used in household wirings like AC outlets, light fixtures, switches, and extension cords. This is the most common size used in household wires today.
  • 11 – 8 – used in light-duty appliances like dishwashers, computers, and small electric equipment.
  • 6 – 4 – medium duty appliances like washers, low-voltages, stoves, freezers, and water heaters.

12 Gauge Vs. 14 Gauge Wire

What is the difference between 12 and 14-gauge wires? Well, it is the thickness of each wire.

Generally, 14 gauge wires are thinner than 12 gauge wires and are used for carrying less current. 14 gauge wires can handle less electrical power (amperage).

If you had two appliances like a washer and dryer, both might use 15 amps, but you don’t want to run them on the same circuit, as the total load would exceed 25 amps.

A workaround here would be to have 12 AWG wires.

Why? Well, 2.5 meters of 14 AWG carries 13 amps, whereas a few more feet of wire will make a difference, providing more space for the current to flow freely.

Recommended Wire Sizes For 200 Amp Electrical Service

What Is A Voltage Drop?

A voltage drop is a difference between the voltage measured at the line and the voltage measured at the device. Voltage drop is usually caused by a mismatch of cable gauge and current flow.

The thicker your wire is, the less electric current can flow through it.

A thick wire with current passing through won’t carry as much power as a thin wire.

Voltage drops occur when there is too much resistance in your circuit thanks to the larger gauge wires needed for your application.

The same amount of electricity moves along slowly if the resistance is higher, this effect relates to length and the area or diameter.

Resistance also increases when the temperature rises and the length of the run.

Extra voltage drops are created in longer wires thanks to internal resistance, and power can be lost here because of this.

To measure your voltage, you can use a multimeter. This can help you to see if you have any voltage drops and identify the possible cause of this.

What Is More Important Than Voltage Drop In Electric Circuits?

Voltage drops aren’t the only thing you need to keep an eye on!

You also need to look at current losses in your electric circuit. A voltage drop affects the power factor and does not cause a huge amount of energy loss in your systems.

When it comes to your circuits, most people focus on getting as much out of them as possible, rather than making them efficient.

Most electricity handouts will tell you you should use large wires for high-current applications and pair them with larger gauge wires, due to the voltage drop.

While this is true, it isn’t the only way to consider our energy and we can also look at the energy moving in and out of the wire.

If your system has a low-voltage DC (like a 12V) system that has a voltage drop, you should opt for larger wires.

These will avoid voltage drop and keep maximum power going into and coming out of the circuit.

While you will lose some power from resistance, if you increase your wire size to ½ inches, you will lose 0.1% of the power going in and 0.5% of the power coming out compared to smaller wires.

The voltage drop is proportional to resistance here, which is why you see less power being lost! Again, you can use a multimeter to measure the voltage drop in your circuits.

What Size Wire For 20 Amp Wire Size

15 Amp Breaker Wire Size

15 amp breakers will need a 12 gauge wire. If you have a 10 amp circuit, you will need a 145 gauge wire.

The wiring in your home has little resistance built into it, especially if your wires are 20 years old or older.

The breaker will only be able to use 2 amps, so you don’t need to worry a lot about voltage drops from resistance here!

What Is An Electrical Box?

Now, we bet you are wondering what an electrical box is. Well, there is a box that acts as a structure for the circuit breaker.

It is also an enclosure that will protect your circuit breaker. If you are working with metal boxes too, electrical boxes will act as a grounding point.

Should I Use An Enclosure?

Do you need to use an enclosure? The answer varies, but often, it is yes! Your enclosure protects the circuit breaker, increasing its longevity.

If you have an electrical box that isn’t designed to be used as an enclosure, there are some ways you can effectively use one! Check out our tips below.

Use The Box As An Enclosure

You can use your metal box as an enclosure. These will usually have tabs on the back side, allowing you to mount them directly to another surface.

You can mount them to wood studs or drywall with ease. If you have not mounted metal boxes before, you can enlist the help of a professional to do so.

Mounting Brackets

Another option is to use mounting brackets.

This avoids the need for you to mount the box directly to your wall, and can be an easier option, especially if you are scared about taking the drill to your wall!

Mounting brackets can be purchased from most hardware stores, or online for an affordable price.

Mounting brackets tend to be easier to install, but you can also enlist the help of a professional if you have never used them before. Why should you use mounting brackets?

Well, if you are doing wiring outside, metal boxes should be used.

These will provide better cover and durability for your wires, protecting them from adverse weather, like harsh winds and rain.

You should opt for metal, over plastic covers. Plastic, or PVC covers can deteriorate quickly and could even cause a fire hazard!

If your wires get wet, you run the risk of water damage or an electrical fire. It is not worth the risk, so be sure to use a metal enclosure.

For any wiring that is done outside, you need an enclosure to protect your wires!

Final Thoughts

And there you have the answer to what size wire for 15 amps! For 15 amps you can use a 14-gauge or a 12-gauge wire.

Be sure to check what size wire your breaker needs before making your choice to ensure that you are making the right choice.

Be sure to check out our tips and tricks (see also: How To Winterize Your RV: Checklist, Tips & Tricks)when it comes to protecting these wires and getting the most out of them to ensure that your wires are working smoothly and there are no dips in voltage or current!

Eddie Meyers
author avatar
Eddie Meyers
My name is Eddie, and I am an RV enthusiast! I have enjoyed traveling all my life, and want to give my family the same opportunities to see as much of the world as possible. As I’ve gotten older, I’ve discovered how great RVs can be for vacations with a young family. Here at RV Lifestyle Experts, I want to share my experiences, the tips I’ve picked up along the way. I hope that our guides can encourage you to try the RV lifestyle. I promise you that you won’t regret it!
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