The wire gauge is probably the most important aspect of your electrical system. You could burn your house down simply because you chose the wrong wire size. Some people ignore the wire gauge where lights are concerned, but that is a mistake. Thin wires in an extensive lighting system are dangerous because they can overheat if you overwhelm. But what is the correct wire size? How do you select the gauge of a 12V light? This guide will answer those questions.
What Gauge Wire For 12V lights?
- 60W 5A light requires 16 AWG to run for 15 ft, 14 AWG for 20-25 ft, 12 AWG for 30-40 ft, 10 AWG for 50-70 ft, 8 AWG for 80-90 ft
- 120W 10A requires 12 AWG to run for 15-20ft, 10 AWG for 25-30 ft, 8 AWG for 40-50 ft, 6 AWG for 60-80ft, 4 AWG for 90 ft
- 180W 15A requires 10 AWG to run for 15-20ft, 8 AWG for 25-30 ft, 6 AWG for 40-60 ft, and 4 AWG for 70-90ft.
- 240W 20A requires 10 AWG to run for 15 ft, 8 AWG for 20-25ft, 6 AWG for 30-40ft, 4 AWG for 50-60 ft, 2 AWG for 70-90 ft
- 300W 25A requires 8 AWG to run for 15-20ft, 6 AWG for 25-30 ft, 4 AWG for 40-50ft, 2 AWG for 60-80 ft, 1 AWG for 90 ft
- 360W 30A requires 8 AWG to run for 15ft, 6 AWG for 20-25 ft, 4 AWG for 25-30 ft, 2 AWG for 40-50 ft, 1 AWG for 60 ft, 1/0 for 70-80 ft, 2/0 AWG for 90 ft.
- 600 W 50 A requires 6 AWG to run for 15 ft, 4 AWG for 20-25 ft, 2 AWG for 30-40 ft, 1 AWG for 50 ft, 1/0 AWG for 60 ft, 2/0 for 70-80 ft, 3/0 AWG for 90 ft.
- 720 W 60A requires 4 AWG to run for 15-20 ft, 2 AWG for 25-30 ft, 1 AWG for 40 ft, 1/0 AWG for 50 ft, 2/0 for 60-70 ft, 3/0 for 80-90 ft
The wire gauge you select depends primarily on the amount of power a light uses, not the type of light. Therefore, if you want to identify the appropriate gauge for your home’s lighting system, you have to keep the following in mind:
1). Light Type
The light’s power rating is more important than the type of light. However, the lighting type still matters because it affects the overall energy consumption.
For instance, if you have a conventional fluorescent bulb, you should take note of the bulb’s watt rating. However, if you have a strip of LED lights, you must consider the length. The average strip consumes a certain amount of power per foot. Therefore, to get the total wattage, you should multiply the watts per foot by the length of the light strip.
If you have multiple fluorescent bulbs, the same concept applies. Get the total wattage of all the bulbs.
2). Amp Rating
The total wattage won’t tell you anything. You have to identify the amp rating. This means dividing the total wattage by the voltage (12V) to get the amperage.
3). Chart
Once you have the amp rating, you can use the table published below to find the wire gauge. If you can find the amp rating you calculated in the table, it won’t take you long to locate the corresponding wire gauge.
| Length | 5 Amp 60W | 10 Amp 120W | 15 Amp 180W | 20 Amp 240W | 25 Amp 300W | 30 Amp 360W | 40 Amp 480W | 50 Amp 600W | 60 Amp 720W |
| 15 Ft | 16 AWG | 12 AWG | 10 AWG | 10 AWG | 8 AWG | 8 AWG | 6 AWG | 6 AWG | 4 AWG |
| 20 Ft | 14 AWG | 12 AWG | 10 AWG | 8 AWG | 8 AWG | 6 AWG | 6 AWG | 4 AWG | 4 AWG |
| 25 Ft | 14 AWG | 10 AWG | 8 AWG | 8 AWG | 6 AWG | 6 AWG | 4 AWG | 4 AWG | 2 AWG |
| 30 Ft | 12 AWG | 10 AWG | 8 AWG | 6 AWG | 6 AWG | 4 AWG | 4 AWG | 2 AWG | 2 AWG |
| 40 Ft | 12 AWG | 8 AWG | 6 AWG | 6 AWG | 4 AWG | 4 AWG | 2 AWG | 2 AWG | 1 AWG |
| 50 Ft | 10 AWG | 8 AWG | 6 AWG | 4 AWG | 4 AWG | 2 AWG | 2 AWG | 1 AWG | 1/0 AWG |
| 60 Ft | 10 AWG | 6 AWG | 6 AWG | 4 AWG | 2 AWG | 2 AWG | 1 AWG | 1/0 AWG | 2/0 AWG |
| 70 Ft | 10 AWG | 6 AWG | 4 AWG | 2 AWG | 2 AWG | 2 AWG | 1/0 AWG | 2/0 AWG | 2/0 AWG |
| 80 Ft | 8 AWG | 6 AWG | 4 AWG | 2 AWG | 2 AWG | 1 AWG | 1/0 AWG | 2/0 AWG | 3/0 AWG |
| 90 Ft | 8 AWG | 4 AWG | 4 AWG | 2 AWG | 1 AWG | 1/0 AWG | 2/0 AWG | 3/0 AWG | 3/0 AWG |
For instance, a 5A lighting system requires 16AWG at 15 feet. But that figure jumps to 14AWG for 20 feet.
Keep the temperature rating in mind. You need higher temperature ratings for conductors that have to pass through unventilated settings that permit the heat to accumulate.
It is also worth noting that light fixtures typically require thinner wires than other devices in a home because their electrical draw is relatively low. However, if you expect other devices to run on that same circuit, it makes more sense to use thicker wires that can carry the combined load of the lighting system and every other device you choose to connect to that circuit.
This is why I suggest you use anywhere between 10 and 22-gauge cables for lights. This range is quite broad because you also have to account for homeowners that prefer to place the lights and outlets on the same circuit.
A wire size that can comfortably accommodate the lights in your home may overheat because of the heavy-duty appliances you’ve plugged into the outlets.
Things To Consider Before Buying Wire For 12V Lights
The best thing to do is to consult an expert. Let your local electrician select the wire size after inspecting your lighting system. If you don’t have the option of consulting an expert, keep the following factors in mind before you make a decision:
1). Does Amp Matter?
The ampacity is vital. Every cable you see in a store is designed to carry a certain amount of electricity. If you force a wire to carry excess current, it will overheat and melt.
If you’re lucky, you will destroy the wire and nothing else. However, it is pretty common for overheating wires to ignite the objects in the vicinity, starting a fire. The wire may not reveal the ampacity, but you will see the gauge on the cable’s jacket.
You can use that gauge and a chart to find the cable’s amp rating. Once you know the amp rating, you can compare it to the wattage of the lights to determine whether or not the wire is appropriate.
The wire’s rating should exceed the wattage of the lights. Again, you have to convert watts to amps before proceeding.
2). Does Distance Matter?
Pay close attention to the wire length because it affects the resistance. You need a long cable to cover a large distance.
However, before buying that long cable, you must realize that higher resistance in a long line can lead to overheating. This is why electrical professionals respond to long distances by increasing the gauge.
They know that you can increase the length of a thick cable without raising the resistance to dangerous levels. Long distances are not a problem if the gauge is high enough.
3). Does Material Matter?
The material matters because it affects the gauge. Copper has superior conductivity to aluminum. Unfortunately, copper is also more expensive, which is why so many people flock to aluminum.
But if you want to use aluminum, you must increase the gauge because it is less conductive. However, thicker wires are problematic. Even if you switch to aluminum, which is cheaper, thicker cables are not as flexible. This can present a challenge for homeowners that want to pull their wires through a conduit.
4). Do The Conditions Matter?
Thick, heavily insulated wires are the best choice for outdoor lighting because they have to withstand extreme conditions like direct sunlight and snow.
On the other hand, you can afford to install thin wires indoors because the conditions are relatively friendly.
5). Does The Temperature Matter?
There’s a reason why NEC tables mention temperature ratings in relation to the wire gauge and ampacity. They know that wires with higher temperature ratings can carry more electricity than conductors with a lower temperature rating.
6). Does The Ventilation Matter?
Wires that have to lie behind walls or underground are more likely to overheat because they don’t have proper ventilation. The heat is more likely to accumulate. This gives you two options:
- Less Current
You can choose to reduce the amount of electricity the wire will carry. This will prevent overheating because the volume of current passing through a conductor directly affects the amount of heat it produces. In other words, more electricity means more heat.
- Higher Rating
You can buy a thicker wire with a higher temperature rating. Conductors with higher temperature ratings can operate at higher temperatures without overheating.
7). Does The Wire Type Matter?
The wire type doesn’t have a significant impact. You have to choose between solid and stranded wires. Solid wires have one solid conductor, whereas their stranded counterparts consist of bundles of wires.
Stranded conductors have better flexibility, but that can make them more challenging to install.
What Does NEC Say About It?
Once you identify the total wattage of all the lights in your home, convert the figure into amps. You can use the NEC’s table to find the appropriate wire size for your home’s lighting circuit. 14-2 Romex is the perfect gauge for lighting circuits.
Does 12V LED, RV, Landscape Light Make A Difference in Wire Size?
The most important factor is the amp rating. If the 12V LED lights in your home and the fluorescent lamps in your RV have similar amp ratings, you can install the same wire size. The gauge is determined by the light’s power rating, not the type of light.
Can I Use Speaker Wire For 12V Lights?
You can use speaker wire for 12V lights. Speaker lines are thin, but many lights are low-duty devices, especially LEDs. They don’t use enough electricity to overwhelm speaker wires.
But the gauge is the deciding factor. Have you looked at your light’s watt rating? How much power does it use? What about the wire’s gauge? Have you checked the NEC’s charts? How much electricity can the speaker’s wire carry?
Make sure the speaker’s wire is thick enough to accommodate the lights. Some LEDs don’t use enough current to cause overheating in thin cables. However, the wire gauge can affect the brightness.
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