Don’t Use Romex for Solar Panels! (Use These!)

Is Romex wiring good for installing solar panels? While the conversation regarding which wiring type is best for installing solar panels is ongoing, Romex wire remains at the center of this debate. Romex is mainly used in:

  • Residential property
  • Commercial property

Did you know that despite being common in some residential and commercial solar installations, Romex is not suitable wiring for outdoor applications?

In this article, you will be surprised just how potentially dangerous it is to use Romex wire when installing solar panels.

Romex cable wire

An Overview of Romex Wiring

Romex wire is one of the most popular types of wiring that is common in most households. The wire is technically a non-metallic sheathed cable that is part of the electrical system used by many house owners and businesses. 

The cable contains more than one conductor that is housed in a flexible plastic sheathed. The good thing about Romex wire is that it can be run through walls, attics, under floors, and many other areas during construction. 

One of the most important things to know about Romex wiring is that it is largely designed to be used indoors.

This means that you have to exercise caution when using this kind of wiring in conditions that might expose it to adverse weather conditions such as use in solar panels. 

So many people keep asking whether Romex wire is ideal for use when one is installing solar panels in their commercial or residential properties.

Romex wiring is not rated for wet conditions which makes it unsuitable for the installation of solar panels

When used with solar panels, you risk causing hazards such as fires which is why the monetary benefits you might be seeking when using Romex wiring when installing solar panels might not be worth it.

What is Romex Wire Good For?

Romex wires are very common in construction but what are they? Romex wiring is very common in the construction industry for both commercial and residential properties. 

Romex wires are found in a number of gauges with the most common being the 14-gauge and 12-gauge – they range from 3 to 14 gauge with an amp range from 15 to 200. 

The wire is made using copper or aluminum depending on the series. Romex wires have a casing that protects the wire from arks, loss of current, and the typical safety standards. 

A standard Romex wire is either copper or aluminum-made and comes with a PVC coating that enhances the wire’s corrosion resistance. 

While the insulation on the wire is adaptable to wet and damp conditions, the wire itself should not be exposed to water hence its unsuitability for the outdoor environment.

See also: How to install solar panels (Detailed Step-By-Step Guide)

What are Some of the Uses of Romex Wire?

There are different kinds of wiring but Romex wire is majorly for residential or commercial indoor wiring. It also happens to be the wire of choice for people constructing temporary structures that will require them to move after a short period of time. 

The main reason why construction managers and owners are discouraged from using Romex wire is that the wire is not rated for outdoor use.

If you are setting up an outdoor solar installation on your building after construction, then you should never use Romex wire.

Why Romex Wire is Unsuitable for Solar Panels Installation?

Despite having a PVC insulator, Romex wire is unsuitable for use in solar panel applications. Despite having a PVC insulator, this insulator is likely to deteriorate with time exposing the wire (made from steel) inside to wet and damp conditions. 

Once this happens, the steel wire will corrode or rust, increasing the likelihood of the wire sparking electrical shorts in wet conditions.

Potential hazards from using Romex wire in an outdoor environment include:

  • Electrical shock
  • Heat buildup
  • Fire
  • Short-circuiting
  • Overloads

Although it has a protective coating, Romex is not designed for outdoor use. 

Using a Conduit in Romex Wiring

During the installation of solar panels on residential and commercial buildings, there is always the temptation of using Romex wire because it is economical. 

Most people will be tempted to still use Romex wire but use a conduit as a way to avoid potential hazards attributed to using the wire outdoors.

However, using a conduit is a short-term solution since the wire is also not designed to be buried inside a conduit. 

Instead of trying to repurpose the wire to suit the outdoor environment for the installation of solar panels, use a wire that has an outdoor rating and can survive wet conditions without causing any potential risk.

Which wiring Type is Suitable for Solar Panels Installation?

When wiring a solar panel, the best wire used is either a copper or an aluminum wire. 

While aluminum is ideal for all weather conditions in solar panel applications, copper wires are best suited when used in a conduit as their gauge as metals happen to be higher than that of aluminum. 

When used for residential purposes, MC cables are the preferred choice since they are rated for use in outdoor conditions and also come with conductors made from copper or aluminum and rubber insulation. 

For solar installations, it is advisable to use a wire that has been tested to ascertain whether it meets the standard requirements for electrical wires or not. 

Higher-end residential solar installations tend to use copper wire based on the fact that copper is a better conductor than aluminum

This is the reason why you are likely to find most solar installations in residential buildings using Photovoltaic (PV) wire. This is the kind of wiring that is mainly designed for solar installations.

Photovoltaic Wire in Solar Installations

Photovoltaic (PV) wire is the preferred wiring type for both commercial and residential installation of solar power. 

The reason for this is because the wire is made from copper but also has a steel or aluminum core. It also comes with water-resistant insulation that can withstand damp and wet conditions. 

An important feature of PV wire is that the outer layer of the wire has a ribbing that protects the wire from abrasion. However, PVC wire is not ideal for long distances or high voltage currents. 

PV wire also has its downside where the water-resistant coating eventually deteriorates exposing the copper wire inside-something that may lead to electrical shorts when the wire comes into contact with water.

Solar Panel Wire

If you are wondering whether Romex wire is ideal for solar power applications, its suitability will largely depend on where it is being used in the solar installation setup. 

Just know that it is not advisable to use Romex wire outdoors but can be used indoors during the installation of solar panels. 

At the very least, always try to use the kind of wiring that is recommended for outdoor conditions when it comes to solar power.

At the very least, always try to use a type of wiring that is rated for outdoor use when it comes to solar panel installations. And one that is going to last the 25-year lifespan.

Here are some images of solar panel wire from Amazon – click to view more.

TEMCo 100' Red + 100' Black 10 AWG/Gauge Solar Panel Extension Cable with M/F Solar Connector Ends (Variety of Lengths Available)

TEMCo 100' Red + 100' Black 10 AWG/Gauge Solar Panel Extension Cable with M/F Solar Connector Ends (Variety of Lengths Available)

TEMCo 100' Red + 100' Black 10 AWG/Gauge Solar Panel Extension Cable with M/F Solar Connector Ends (Variety of Lengths Available)


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Elliot has 20+ years of experience in renewable technology, from conservation to efficient living. His passion is to help others achieve independent off-grid living.

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