What Size Wire Do I Need for a 100 Amp Service?

What Size Wire for a 100 Amp Service?

100 amp wires

A #2 AWG wire is needed for a 100 amp service. This wire is used when the run between the breaker panel and the electrical load (such as an air conditioner) is long, like in large commercial buildings. A #4 AWG wire can be used if the distance between the breaker panel and the electrical load is less than 50 feet.

Where is 100 amp service used?

Here are some of the places where 100 amp service is used:

  • Mid-size homes and apartments
  • Older homes with a limited number of appliances
  • Detached garages
  • Workshops
  • Agricultural facilities
  • Temporary power at construction sites
  • Subpanels and circuit breaker panels in residential, commercial, and industrial buildings

100 amp service is a very common type of electrical service, and you can find 100 amp subpanels everywhere.

Ground wire size for 100 amp service

The minimum size for a 100 amp ground wire is #8 copper or #6 aluminum.

Want to know the wire sizes of other amperages? Visit some of our other pages below.

Here are some of the best 100 Amp Rv wires and circuit breakers you can buy today

  • 2 Gauge 2 AWG 20 Feet Black + 20 Feet Red

  • 2 awg wire on amazon

    This 2AWG wire is perfect for transferring power from a battery bank to a electrical equipment. It is ideal for marine, RV and automotive applications. Copper cable is fully annealed per ASTM standards. Complies with SAE J1127. Has a tough, solvent resistant EPDM insulation jacket and is rated to handle up to 600 volts at 105 degrees Celsius. This 2AWG wire is highly flexible, making it easy to route your wiring in engine compartments and other tight spots which may not be possible with larger gauge cables.

  • EWCS 2 AWG UL Approved Marine Grade Tinned Copper Wire

  • 2 awg 600v wire

    Made in the USA. This marine grade wire is tinned for corrosion protection and will always be highly recommended for salt water areas, marine environments and other corrosive applications. It exceeds SAE and ABYC standards and is rated to handle up to 600 Volts. This type of wire easily resists Abrasion, Acid, Alkali and Gasoline.

  • Q2100 100-Amp Double Pole Type QP Circuit Breaker

  • 100 amp circuit breaker

    The Siemens double pole, 100-amp Q2100 circuit breaker is used for overload and short-circuit protection of your electrical system. This black breaker is rated for 10,000 amperes and features a thermal-magnetic tripping mechanism. The Q2100 circuit breaker requires only 1/2 In. per pole for wire bending space and has a maximum load of 240 VAC. It works in Siemens PL and ES series load centers. The size of the Q2100 circuit breaker makes it easy to install and easy to use in Siemens enclosures or panels. It provides easy plug-in connections in Siemens enclosures and the time saving Insta Wire feature enables the user to connect wires without turning off the main power (120V/240V). Circuit breakers should only be replaced with new tested and Safety Agency Listed circuit breakers, never use recycled breakers.

    The 80% NEC Requirement

    The wire size for a 100 amp breaker should meet the 80% NEC requirement, which means the wire should be able to handle a current of at least 80% of the breaker's capacity. The wire sizes that meets this requirement is as follows:

    • #4 AWG can handle up to 85 amps, which meets the 80% requirement for a 100 amp breaker.
    • #3 AWG can handle up to 100 amps, which meets the requirement exactly.
    • #2 AWG can handle up to 115 amps, which exceeds the requirement.
    • #1 AWG can handle up to 130 amps, which exceeds the requirement.

Is copper wire safer than aluminum wire?

copper wire vs aluminum wire

These two types of wires are similar in resistance and can be used interchangeably with no ill effects, though aluminum will cost less due to its lower material costs.

Copper Wire: Rated at 100 amps and can carry anywhere between 80-95 Amps of continuously loaded current. Copper wire is more expensive than aluminum wire, but looks nicer when strung together on poles. Aluminum wire: Rated at 100 amps and can carry between 94-105 Amps of continuously loaded current. Aluminum wire is less expensive than copper wire, but looks uglier when strung together on poles.

Is aluminum the better choice for overhead power line conductors?

No, copper is the better choice because it has more conductivity than any other metal. This means that it will allow for more efficient transmission of electricity which in turn makes more economical sense for utility companies to use. Aluminum wire may be used as a cheaper substitute for copper wire, but its inferior conductivity means that it must be replaced with far greater frequency; this adds yet another expense to an already expensive project.

On icing conditions - under heavy snow at cold temperatures (below 10 degrees F) both aluminum and copper lose around 10% of their resistance. This means that at a given voltage, the current will be more than if no snow was on the wire. In practice this does not happen because very few HV lines are operated at a fixed voltage - they have droppers which control the voltage from line to line and from line to ground until it reaches the required level for that load on that circuit. Copper has higher conductivity, therefore copper wires of a given size give a lower temperature rise in normal conditions compared to aluminum wires of similar sized.


To conclude this blog post, you have learned that #2 AWG is the perfect 100 amp wire size. Also, aluminum wiring is a viable option for houses where copper prices are high, but the superheat requirement of aluminum wire limits it's use in some cases.

Thank you so much for reading this article on Aluminum Wire Vs Copper Wire For 100 Amp Service, hopefully you found it helpful and informative.

15 Amps

All you need to know about using 15 amps. Click to find out.


About Author:

image of Kevin Pommells

Hi, I'm Kevin Pommells, a lover of camping and the great outdoors as everyone says nowadays. I'm also a passionate soccer fan and the proud owner of CamperRules.com, a website dedicated to helping campers and outdoor enthusiasts make the most of their adventures. With years of experience exploring the wilderness and a deep love for the sport of soccer, I'm always looking for new ways to combine my two passions and share my knowledge with others. Follow me for tips, tricks, and insights on all things camping and outdoor recreation.

Follow Me @ Twitter | Facebook

As an Amazon Associate I earn from qualifying purchases.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.