THHN Vs THWN Wire – Are They The Same?

Choosing which wire is suitable for your project can be quite confusing in the world of electrical wires.

Among them, some wires carry acronyms for their names which may present them as different wires, but in reality, they are used for the same purposes. THHN vs THWN both fall under that category.

THHN and THWN wires are single-conductor wires used in industrial buildings and residences to deliver electricity.

THHN stands for Thermoplastic High Heat-resistant Nylon-coated wire, whereas THWN stands for Thermoplastic Heat and Water-resistant Nylon-coated wire. So, the key difference between these wires is that THWN is water resistant, and THHN is not.

However, this is not enough to decide which wire to choose for certain projects. Stick with me until the end to know which wire you should pick for your task.

7 Comparison Factors Between THHN And THWN Wire

Voltage Rating600 Volts600 VoltsBoth
Heat-Resistance90° Degrees on dry condition
75° Degrees on moist condition
90° Degrees on dry condition
75° Degrees on moist condition
ApplicationResidential and Commercial wiringResidential and Commercial wiringBoth
InsulationNylon-coated PVCNylon-coated PVCBoth
TypeHot, Neutral, GroundHot, Neutral, GroundBoth

Now let’s dive into the details to know both these wires better.

Comparison Factor 1: Voltage Rating

Voltage rating indicates the maximum capacity of a wire to carry voltages in a wiring system.

THHN and THWN have a voltage rating of 600 Volts, which means you can apply up to 600 Volts on both wires in cable construction.


THHN and THWN cables have copper conductors that can carry up to 600 Volts without any issue.

Comparison Factor 2: Heat-Resistance

THHN and THWN wires have a nylon coating over Thermoplastic insulation, making them highly resistant to heat.

THHN wires can function at 90° Celcius under dry conditions and 75° Celcius under moist conditions. However, using THHN wires in wet environments is not recommended as they are not waterproof.

THWN wires also have a temperature rating of 90° Celcius in dry environments and 75° Celcius in moist ones. But this wire has a successor, THWN 2, rated up to 90° Celcius for both dry and wet environments.


As you can see in the name, THHN is made for resisting high heat. So, it can be considered a little better than THWN in this criteria.

But both of them serve their purpose equally under dry conditions.

Comparison Factor 3: Water-Resistance

Per our earlier discussion, we already know that THHN is highly heat-resistant but not recommended for wet locations.

You have to run it through a conduit to install them in a moist environment. Thus, THHN is not waterproof.

On the other hand, THWN wires are jacketed with thermoplastic and a nylon coating, making them highly water-resistant and perfect for use in moist and wet locations.


Undoubtedly, the winner in this segment is THWN wire, as they are built to resist water.

Comparison Factor 4: Conductor

Wires can have multiple conductors inside their jackets. But THHN and THWN both wires are single-conductor wires which are either made of copper or aluminum.

The conductor can be solid or stranded, depending on the wire’s size.


Both wires have one single conductor, so their performance rating will also be the same.

Comparison Factor 5: Application

THHN and THWN wires are used in building constructions for carrying power between buildings.

However, if the THHN wire doesn’t have a dual rating, it shouldn’t be used outdoors. At the same time, you can use THWN wire both indoors and outdoors without worrying a bit.

Also, THHN wires aren’t recommended to be used in moist locations or any unfinished part of the building where leakage is a possibility.

THWN has no issues like that and can be used in wet locations.


Judging by the ability to work under any condition, I would give this round to THWN wire for having versatile applications.

Comparison Factor 6: Insulation

THHN and THWN, both wires, have nylon-coated PVC insulation.

This means both of these wires are grease, chemical, and oil-resistant. They also have passed the FT1 flame test, which makes them resistant to high heat.


THHN and THWN wires have the same type of insulation, so they are effective against environmental residues.

Comparison Factor 7: Type

Both THHN and THWN wires have 3 types of wires with different color sheathings – Hot wires, Neutral wires, and Ground wires.

Hot wires are colored black, red, and orange. Neutral wires are colored white and brown, and Ground wires are colored green and yellow-green.

The colors indicate which functions each wire performs in a circuit.


Ideally, there are zero differences in cable types for THHN and THWN wires.

You can use them separately if you are using them for indoor projects or combine them together for outdoor projects.

THHN Vs THWN: Which One To Choose?

When picking wires for your cable construction, it all comes down to the temperature and humidity level of the surroundings.

Now that you know the specific differences between the THHN and THWN wires, let’s see which wire suits different situations.

High Heat Conditions (Above 75° Celcius)

If the surrounding of your cable construction is below 75° celsius, you can go for any of these wires.

On the other hand, if the temperature is higher than this, always pick THHN or THWN 2 wires for their high heat-resistance capacity.

Both of these wires can tolerate up to 90° Celcius temperature.

High Humidity Conditions

If you are working in a wet environment, you should pick THWN or THWN 2 wires as they are fully water resistant.

Also, you can go with THWN wire as it is less expensive than THWN 2 wire.

High Heat And Humidity Conditions

What should you do if the construction site is wet and under high temperatures?

This is certainly the most extreme situation, and whenever this happens, you can use THWN wire if the heat is not too severe.

But if the temperature exceeds more than 75° Celcius, without any doubt, use THWN 2 wire. Because only THWN wires can function under both wet and dry conditions, and only THWN can tolerate temperatures higher than 75° Celcius in wet conditions.

Final Verdict

Whenever you are in a doubt between THHN and THWN wire, you should go for THWN.

Because THWN has both heat and water resistance which THHN doesn’t, however, if you are short on budget and the working site is not wet, you can pick THHN wires.

That’s everything you need to know about the THHN vs THWN wire battle. I hope this article has made your decision process easier.


Is Thhn and THWN wire the same?

THWN and THHN are frequently used interchangeably since they are nearly identical. THWN is a single conductor wire with a nylon jacket and Thermoplastic insulation.

Does THWN require conduit?

THHN must be safely installed into a conduit before being placed underground for outdoor applications. The wire’s nylon coating shields it from harm while it is carried through the conduit.

Can THWN wire be used outdoors?

Wires from THWN can withstand oil. It can therefore be used in both indoor and outdoor settings. On the other hand, THHN wire is best for carrying high amounts of electrical current, up to 600 volts, in commercial and industrial environments.