What type of wire is used for solar panels?

Today we look at the best wire to use for solar panels. The difference will protect you, your panels and produce a better return.

Cables that have very thin insulation, usually a colored sheet to identify the wire’s voltage and wattage.

The monocrystalline solar cells have a “back” contact, made of metal with a lower resistance than aluminum. This type of contact allows for better electrical current flow from the back of the cell to the front, allowing for slightly higher efficiency when converting photons into electricity.

Below are some of the key points that I’ll cover, plus more you’ll need to know;

  • Can you use THNN wire for solar panels?
  • Do solar Panel wires have to be in conduit?
  • What wires should you use for solar panels

Read through the article to find out more about the proper wiring for your solar panel.

Wiring under solar panels

Can you use THNN wire for solar panels?

The answer is no. The THNN wire has a much larger insulating layer on the conductor, which isn’t needed for the lower voltage of a solar panel application.

That insulation would block too much electrical current flow for it to be helpful in a solar panel set.

The THHN wire has a small insulating layer on the conductor, and that insulation is fine for lower voltage solar panel setups.

This could cause some problems, though. The solar panel voltage is around 15 volts, but the power company’s grid has 120 or 240 volts of alternating current.

This means that there will be a significant difference in electrical potential between your home wiring and your solar panels, which would cause electricity to arc through the air from one wire to another if the insulation is not thick enough to prevent this.

(This arcing causes sparks, which can be disastrous if they ignite something flammable.)

Can I use ACSR wire for solar panels?

No. The ACSR wire has aluminum conductors, but those conductors are much thicker to make up for the lack of electrical current flow from an aluminum conductor compared to copper.

You can do calculations as you would for THHN wire to make sure your wires have enough wattage capacity for your application (in this case, a solar panel system).

The cables also have different insulation, usually a colored sheet to identify the wire’s voltage and wattage.

Do solar Panel wires have to be in conduit?

No. If you want to use THHN or THWN (or even ACSR) wire, they need to be in conduit because of the potential for arcing and sparking between wires that could ignite flammable objects nearby.

This is more critical than regular house wiring because solar panels are generally installed up high on top of your roof where there’s nothing but the air that could easily catch fire.

Suppose you’re using MC4 connectors, though. In that case, a conduit isn’t necessary because those connectors have a positive lock that allows them only to touch the negative part of the panel connector.

So no electricity will flow through them if they accidentally come into contact with each other else grounded like your roof or suspect roof.

What wires should you use for solar panels?

MC4 connectors are the most commonly used wires for solar panels because they don’t need to be in conduit, and you can use any old house wire for them.

(Although it’s probably best to stick with THHN or THWN wire, which is what most professionals would do, especially when wiring your home.)

Other MC4 cables are available, but they’re usually more expensive than standard insulated house wires like THHN, THWN, etc.

You can also use non-insulated MC4s if you want to install the wires by themselves without having anything else surrounding them except air, like on top of your roof where there would be nothing nearby that could catch fire even if the insulation were to get knocked off.

How much wattage do solar panel wires need?

This depends on the number of panels in your setup, their total wattage requirement, and the distance between them.

You can find these specs on the panels, usually right around the outside of one of the corners.

If you’re doing a small panel or two to power some lights or charge your electronics, then probably 15-20 amp rated THHN wire would be enough for that distance.

Still, if you have more than that or are planning to expand so eventually you’ll have more solar panels in the future, you may need something with a higher amperage capacity.

It’s best to get wires with more wattage capacity than what is required, though, because it will give you wiggle room when working with electrical calculations, figuring out how long your wires need to be between different parts of your setup, etc.

Can you use Romex wire for solar panels?

No. For several reasons, mainly because all conductors have some resistance, so if you’re wiring up your house with Romex (which has NM-B insulation), there will be too much electricity loss through heat generation, which could cause problems including fires if they get bad enough.

Plus, the thin NM-B insulation isn’t meant to withstand the heat of a solar panel system, so it’s likely to deteriorate over time.

Also, not all types of NM-B have the same fire resistance rating. For example, Romex is only rated for about 3 minutes when exposed to flames.

This means that if you use Romex in a solar panel wiring setup, then your wires will probably melt and catch on fire after being exposed to sunlight for just a few minutes.

How do you hide solar panel wires?

There are a few options to consider, but most people just let them hang down their roof where you can see them or attach them to the house with some mounting brackets.

You could also run the wires through PVC pipe if you want them concealed underneath your shingles…but this is probably best suited for larger jobs because it might be hard to make all the connections with long runs of wire inside PVC pipe.

Keeping your links short will help reduce resistance and increase efficiency, which is essential with solar panels since they’re relatively expensive pieces of equipment that need to produce as much wattage as possible.

Also, using Romex (NM-B) wire isn’t recommended for this kind of wiring job because it’s more likely to catch on fire compared to other types of wiring insulations.

Can you run solar panels inside your house?

Yes, but only if you use an inverter. Standard solar panels don’t produce AC power like household outlets, so you can’t use them directly without one.

An inverter turns DC power from the solar panels into usable electricity that can run any appliance you could otherwise plugin at home: TVs, lights, computers, toasters, space heaters, etc.

Can I use 14 gauge wires for solar panels?

It depends. It’ll depend on the total wattage required by your solar panels, how far apart they are from each other, how long the wires need to be between them and the solar controller/inverter unit, etc.

If you’re doing a few panels, then 14-gauge should be good enough for that distance (or even 12-gauge if you want to save money), but it depends on your setup.

When you lay out all of these different factors, it ends up being an electrical wiring calculation problem; so, hire an electrician or do some research online about using Ohm’s Law to help figure things out (you can find examples in various places).

How do you protect solar panel wires?

If you’re wiring together your solar panel system, then it’s best to use junction boxes (weatherproof or not, depending on where you live) for all of the connections that need to be made.

You’ll probably want to use some conduit if you plan on running wires inside the walls/attic of your house, etc. Conduit is just tubing with openings at each end so you can feed wires through it and seal up both ends with plastic/metal caps.

The gap between these two cap ends is where you can slide in another piece of conduit filled with more wires, which creates a network for carrying electricity throughout your entire system.

It might also be advisable to use thermal insulation to wrap around the actual solar panels themselves if you live in a really hot climate.

Do I have to install a solar charge controller?

Yes, you do. And this component is essential if you want your batteries to survive many years with multiple charge/discharge cycles.

Not all solar panels come with built-in charge controllers, which means that you’ll need an external one to regulate the flow of electricity into your batteries (keeping them from overcharging and causing damage).

Using an inverter instead of directly connecting your solar panel system to household appliances is also better for the battery bank because it reduces how much current gets drawn at any given time.

If your inverter were constantly drawing 120 volts @ 100 amps, 24 hours per day, then things would eventually degrade even further than if you just hooked it up directly to the battery bank.

Can I use regular cables for Solar panels?

Don’t use standard cables. They won’t handle the high currents associated with solar panel systems because they’re not rated for outdoor installation and direct sunlight exposure.

Use cables that are specifically made for outdoor installation, such as MC4 connectors or copper grounding lugs, so you can guarantee they will last a long time.

If you have access to a welder, then you might also want to consider sealing all of your connections together with some metal-to-metal adhesive because it’ll prevent corrosion from forming over time (even if just marginally).

That being said, many people don’t bother to seal their wires together, and sometimes it doesn’t matter as much as you would expect because stainless steel wire is already corrosion-resistant.

What gauge wire should I use for solar panels?

It depends on the total wattage required by your solar panels, how far apart they are from each other, how long the wires need to be between them and the solar controller/inverter unit, etc.

If you’re doing a few panels, then 14-gauge should be good enough for that distance (or even 12-gauge if you want to save money), but it depends on your setup.

When you lay out all of these different factors, it ends up being an electrical wiring calculation problem; so, hire an electrician or do some research online about using Ohm’s Law to help figure things out (you can find examples in various places).

Solar Panel Setup FAQ

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