Here’s a listing of the standard copper service entrance wire sizes for residential 3-wire single-phase service. Wire sizes are AWG (American Wire Gauge), and adjustments may be necessary due to temperature rating or length of wire run. An often-used rule-of-thumb is to jump up one wire size for each 100 feet of a long run.

SERVICE SIZE     WIRE SIZE    

100 amp                    #4 and #3               

125 amp                    #2 or #1            

150 amp                    #1/0            

200 amp                    #2/0            

225 amp                    #3/0 or #4/0 

    The neutral wire is often one or two sizes smaller than the two hots. The correct sizing of the neutral depends on doing a calculation of the “unbalanced load,” which is an estimate of the amount of 120-volt current usage. 

    Wire size may be marked on the side of the cable, followed by the letters “AWG”. But not all cables are clearly marked and sometimes the lettering strip is just not visible. Electricians and experienced inspectors can tell at a glance if the service cable size is correct most of the time. 

    For sizes of aluminum service entrance cables, see our blog post What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?  

    These sizes for service conductors also apply to feeder conductors. Go to our articles What is a service conductor? and What is a feeder conductor? for the difference between the two.

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    Here’s links with answers to some Frequently Asked Questions (FAQ) about ELECTRICAL SERVICE:

• What is the minimum overhead electric service drop height/clearance to a house?

• Why is a leaning electrical service mast dangerous? 

• What is the fireman’s switch emergency disconnect requirement for residential electrical service?

• What are typical copper service entrance wire/cable sizes for the electrical service to a house? 

• What is the minimum clearance of overhead electric service drop wires above a house roof? 

• What is three phase electric service?

• What is a reliable way to tell if the electrical service is 3 phase or single phase? 

• What does it mean when I find buried yellow "CAUTION" tape when digging a hole in the yard?

• How can I find out the size of the electric service to a house?

• What is the difference between the electric service to a mobile home and a site built home? 

• What are the clearance requirements for an overhead electric service drop that is directly over or near a swimming pool?  

• What is the minimum size electric service to a mobile/manufactured home?

• Can anything else be attached to a service mast for overhead electric service besides the service cables? 

• What is the electrical "service point" of a house? 

• Why is there a 3-phase breaker in a single phase panel with only two bus bars? 

• What is the difference between single-phase and three-phase electric service? 

• What is the minimum clearance under an electrical service drip loop of a house? 

     Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.