Wire Size for a Home Electrical Service Panel

By Dave Rongey - Summary:

How to Size Wire for an Electrical Service Panel: What kind of wires do I need to get power to my home?

Wiring an Electrical Service Panel

Electrical Question: What kind of wires do I need to get power to my home?

Project #1: Underground Electrical Service to a New Home

  •  I am building my house in the county side where we have power supply from the main road but I would like to have the supply to the house under ground so it dose not spoil the look of the house.
  • We have to go about 50 meters from supply to house what cable will I need.

This Electrical Panel question came from: Bill, a Homeowner from Saratoga, California.

 Project #2: Electrical Service to a Mobile Home

  • I just got a mobile home and they came to set it up on my land.
  • I need to know what kind of wires I need to get that go from my breaker box outside the home to the mobile home so I can get power turned on at my house.
  • I know I need four kinds of wires, I am just not sure what four.

This electrical wiring question came from Madison , in Vidalia, Georgia.

Dave’s Reply:
Thanks for your electrical wiring questions Bill and Vidalia.

How to Size Wire for an Electrical Service Panel

main electric panel

Application: Installing a Main Electric Service Panel
Skill Level: Advanced – Best installed by a Licensed Electrical Contractor.
Tools Required: Electricians pouch of hand tools and the various power tools necessary for the specific method of electrical service installation.
Estimated Time: Depends on the type of panel, the location, and available access to the project area.
Precaution: This is an extensive project. Working in an electric panel has possible electric arc flash hazards and should be performed by a Licensed Electrical Contractor.
Notice: Installing an Electrical Service Panel should be done according to local and national electrical codes with a permit and be inspected.

Planning an Electrical Service for a Home

In the projects mentioned above there are factors that will determine the type and size of the electrical service to the home, first let’s start with the basics:

The Electrical Service

Terminology and Clarification

  • The Electrical Service refers to the main electrical circuit wires which supply electricity to the home.
  • The Electrical Service is typically provided from the local utility company to a point of connection, and it is from that point of connection that the homeowner or property owner must provide the additional Electrical Service to the main electrical panel of the home.

Overhead or Underground Service

  • The first determination will be if the electrical service will be Overhead, or Underground?
  • Each of these types of electrical service will have a different point of connection to the utility company, which will have an effect on the project overall.

Factors for Sizing the Electrical Service

  • The size of the wire for the electrical service will depend on the size of your main electrical service panel.
  • The size of the main electrical panel will  depend on the size of your home (square foot floor space), and additionally, identify the all of the types of electrical circuits that will be connected to the main panel. This information will also be required by most electrical utility companies so they may correctly size their electrical service to your home. The size of the all air conditioning equipment will affect the size of the service from the utility company, and therefore the size of the home electrical service as well.
  • Once the main panel size has been determined then the distance of the underground or overhead service may be factored in using a few calculations related to the ohms law formula and voltage drop calculations to determine the required wire size.
  • The wire size can only be determined once the above information is verified, and then more decisions can be made about the type of wire that will be used for the overhead or underground service.
  • As you can see, there are several factors that must be identified in order to correctly plan an electrical service project. The Electrical Load Calculator below will help assist you further with this process.

Residential Electrical Load Calculator

  • Electrical Load Calculator

    • The Electrical Load Calculator is a fully functional online and Interactive tool that will assist you with accurate panel load calculations.
    • The Residential Electrical Load Calculator is Pre-Loaded with electrical information for you to chose for typical electrical loads in the home.
    • General Electrical Load Requirements, Appliances and Motor Loads, Heating and Air Conditioning equipment.
    • Sizing Wire for a Panel: Voltage Drop Calculator

More about the Home Electrical Service Panel


  • House Wiring Circuits and Circuit Breakers

  • This article looks at common 120 volt and 240 volt house wiring circuits and the circuit breakers that are installed identifying the types and amperage sizes used in most homes.
  • Electrical Panel Circuit Listing

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» Click here to learn more about Home Electrical Wiring «
  repair electrical wiring  

Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all projects.


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FAQs Frequently Asked Questions and Comments

2 Responses to “Wire Size for a Home Electrical Service Panel”
  1. Dave Rongey says:

    Hi Rich,
    Water corrosion inside a panel can cause extensive damage to the electrical components, so it was good to have the leak repaired and the circuit breakers replaced.
    The ground system of the main service panel is extremely important and must not be compromised. Therefore, if the ground bus has been corroded then it should be cleaned and repaired, or replaced.
    VERY IMPORTANT: The ground system of a panel should never be serviced or disconnected while the main electric service power is on. All methods and components of the ground system must conform to applicable electrical codes and compatible with the electric service panel. This work is best performed by a qualified electrician or licensed electrical contractor.
    Be Safe,

  2. rich says:

    I recently had to go into my 200 amp service panel and noticed that water was coming in through the main service cable. I had that leak fixed, but I noticed that the ground bus and two breakers were corroded. I replaced the breakers. Must I also replace the ground bus? There were no service interruptions and all seems to be doing fine.


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