Virtually all residences have single-phase electrical service. Less than 1%—actually way less than 1%—have three-phase. It is expensive to install and would only be useful if the homeowner had a workshop with large electric motors or the house was a sprawling mega-mansion. Three phase provides higher voltage and its configuration is more efficient for running electric motors.

    But there was a time in the mid-20th century when three-phase service was necessary so wealthier homeowners could run one of those new-fangled central air conditioners. A variant of three-phase called “High-Leg Delta” was required. It is a long-gone bit of electrical history now, and banned by the electrical code for new installations. To read about it, go to our article Why is there a 3-phase breaker in a single phase electric panel with only two bus bars?

     To learn more, go to What is three phase electric service? and What is a reliable way to tell if the electrical service is 3 phase or single phase? and What is the difference between single-phase and three-phase electric service?  

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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 are typical aluminum 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 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 an electrical service drop? 

• 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? 

• What is a service conductor? 

• 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.