Electrical wires vary in thickness depending on their use. While thicker cords are common in power distribution and utility systems, the 18 gauge wire is commonly found in small devices and cars.
We can safely use this wire size if we know how many amps can 18 gauge wire handle. At 90 degrees Celsius, the ampacity of 18 gauge wire made of copper can reach up to 14 amps in a raceway and 18 amps in free air.
Table of Contents
18 AWG Current Rating
The current rating of an 18 gauge copper wire is limited by its thickness. Generally, the larger the cross-sectional area of the wire, the more current it can allow to pass through. However, the more current that passes through a wire, the hotter it gets – a fact that impacts the amp rating 18 gauge wire carry.
Since the size of 18 gauge wire is only around 0.0403 inches in diameter, the US National Electric Code or NEC only rated it up to 14 amps in a raceway or 18 amps in free air at 90 degrees Celsius; these levels of power should prevent the cable from getting too hot.
If the wire gets too hot, it may damage the insulation and create a fire hazard.
To know how many watts 18 gauge wires carry, we need to look at the voltage they operate under. Remember that electrical power is:
Power (watts)= Voltage (volts) × Current (amperes)
So, what is 18 gauge wire good for? You can use it for up to 1680 watts at 120 volts and 3080 watts at 220 volts. However, this cable size is more commonly used in low voltage applications, and if you need a cord that will handle more power, you can switch to a 16 gauge wire.
Factors Affecting 18 Gauge Wire Amps
Two factors may be looked at when we consider the current flowing in an 18 gauge wire – the type of insulation and the length. The maximum current is established to prevent melting insulators, while the actual current flowing through the wire is affected by the voltage drop caused by wire length.
1. Different types of 18 gauge wire
18 gauge wires may come with different types of insulating materials. The NEC lists the following insulators based on the current rating of the wire, but we’ll focus on the two common materials used – thermoplastic PVC and cross linked polyethylene (XLPE).
|Temperature (⁰C/⁰F)||90 ⁰C (194⁰F)|
|Insulating material (wire type)||ZW-2, XHWN-2, XHWN, XHHW-2, XHHW, XHHN, Z, XHH, USE-2, THWN-2, THW-2, THHW, THHN, TBS, SIS, SA, RHW-2, RHH, PFA, MI, FEPB, FEP|
|18 AWG ampacity||14 (in a raceway or buried underground)|
The thermoplastic PVC family includes THWN-2, THW-2, THHW, and THHN. These have insulations made with PVC that is cheap yet flexible and strong. Sometimes, this type is coated with nylon (the “N” part in the label) for added abrasion resistance.
The thermoset cross linked polyethylene (XLPE) family includes XHWN-2, XHWN, XHHW-2, XHHW, and XHHN. They are thicker but more flexible and resistant to external elements than the thermoplastic PVC type.
In fact, thermoset wires handle excess temperatures better than thermoplastic ones. As a result, they can tolerate higher fault currents. For instance, XHHW-2 wires may withstand up to 250℃ while their THWN counterparts max out at 150 degrees.
2. Length of wire at different amps
Another factor to look at will be the length of the wire. While it does not change the amp rating of the wire, it can cause a large voltage drop if the run is extensive. This leads to a lower performance of the appliance.
Since 18 gauge copper wires are common for low voltage use, here is an estimate of how long an 18 gauge automotive wire would span at 12 volts. We listed up to 14 amps, since it’s the wire gauge max amp rating in the NEC. We also limited the runs to a 3% voltage drop:
|Current (amps)||Length (ft) at 12v|
Here are the estimates for 24 volts, especially common for trucks. RVs, and trolling motors for boats:
|Current (amps)||Length (ft) at 24v|
3. Uses of 18 gauge wire
18 gauge wires have a lot of uses. You may not find them within walls, since thicker gauges are used for applications like outlets for 15 amp and 20 amp circuits. However, 18 gauge wires can be found in different appliances, such as cords for 10 amp lights.
They also appear in low-voltage setups like speaker wires, especially for home theaters and car radios, and are also common in toys like model trains and robotics. Interestingly, they can be found in alarm systems and motion sensors too.
Frequently Asked Questions
What is 18 gauge wire? What is it used for?
18 gauge is around 0.0403 inches thick, and is thicker than 20 gauge or 22 gauge. It is used in low voltage applications like remotes and door bells, aside from the uses we mentioned above.
What are the benefits of understanding amps for 18 gauge wire?
Generally, knowing when to use 18 gauge wires and other wire gauges will help prevent fire hazards. The reason is the right cable size will handle your appliance loads without fraying or overheating.
Even though 18 gauge wires may not be found within the walls of a home or a commercial building, they are useful for common household items with their 14 amps capacity.
With the right length and insulation, the proper use of this wire type can prevent fires and other hazards. You only need to know how many amps can 18 gauge wire handle.
I am Edwin Jones, in charge of designing content for Galvinpower. I aspire to use my experiences in marketing to create reliable and necessary information to help our readers. It has been fun to work with Andrew and apply his incredible knowledge to our content.