Every US home gets its power through one doorway: the service entrance. It is the wires and boxes that carry electricity from the utility pole or underground line into the main breaker panel. The meter base sits in the middle of that path and holds the meter that measures how much energy the home uses.
What Is a Service Entrance?
The service entrance is the whole path from the utility supply to the main panel. For an overhead supply it starts at the service drop, the wires from the utility pole to the house. For an underground supply it starts at the service lateral, the buried cable from a transformer to the house.
The meter belongs to the utility, but the meter base and panel usually belong to the homeowner.
The Parts of the System
The service drop and weatherhead. The overhead wires from the pole are the service drop. They connect at the weatherhead, a fitting that points downward so rain cannot enter the conduit, and each wire forms a drip loop so water drips off.
Service-entrance conductors. These wires run from the weatherhead or lateral to the meter base and then to the main disconnect. They are sized for the full service rating, for example 100, 200 or 400 amperes.
The meter base (meter socket). This metal box has spring-loaded jaws that grip the blades of the utility meter. Power flows in through the line terminals at the top and out through the load terminals at the bottom.
The main disconnect. This switch or main breaker shuts off all power to the home in one action. Under NEC 230.70 it must be readily accessible, outside the building or inside nearest the point where the conductors enter.
The grounding electrode system. At the service, the neutral is bonded to ground and connected to electrodes such as ground rods. This connection, covered by NEC Article 250, gives fault current a path back to the source so a breaker trips quickly.
Diagram: The service entrance path. Power flows from the pole through the service drop and weatherhead, down to the meter base, then through the main disconnect to the breaker panel.
How Power Flows Through the Service
Power starts at the utility transformer, which steps the distribution voltage down to 120/240 volts. The service drop brings two hot legs, L1 and L2, and a neutral to the weatherhead. Each hot leg measures 120 volts to the neutral and 240 volts to the other hot leg, the split-phase supply used in almost every US home. From the meter base the conductors continue to the main disconnect, which energises the panel bus bars. Opening the disconnect cuts power to the whole house at once.
Ratings and NEC 230 Rules
The service rating is set by the main disconnect and the conductors. For a one-family dwelling, NEC 230.79(C) requires a minimum of 100 amperes, and most new homes use a 200-ampere service. A larger home with electric heating, a heat pump, an EV charger and an electric range may need 320 or 400 amperes. Article 230 also requires clearance above roofs and driveways, and clear working space under NEC 110.26, at least 3 feet deep and 30 inches wide, in front of the equipment.
Diagram: Inside a meter base. The line terminals at the top receive power, the meter jaws hold the meter, the load terminals at the bottom feed the main disconnect, and the neutral is bonded to ground.
Key Takeaways
The service entrance carries power from the utility to the main panel, through the service drop or lateral, the weatherhead, the meter base and the main disconnect. The meter base holds the utility meter between its line and load terminals, and the main disconnect under NEC 230.70 is the single switch that can cut all power to the home. A dwelling service must be at least 100 amperes under NEC 230.79(C), with 200 amperes standard in new homes. Never work on the service entrance yourself: everything before the main disconnect stays live even when the panel breakers are off.
Objective Questions
1. What is the meter base in a US home electrical service?
a) The main breaker panel inside the house
b) A metal box with jaws that holds the utility meter between the line and load terminals
c) The transformer on the utility pole
d) The grounding rod driven into the earth
Answer: (b) A metal box with jaws that holds the utility meter between the line and load terminals
Explanation: The meter base is the socket that holds the utility meter, with power entering through the line terminals and leaving through the load terminals.
2. According to NEC 230.70, where must the service disconnect be located?
a) In the garage only
b) At a readily accessible location, outside the building or inside nearest the point of entrance
c) On the utility pole
d) In the bedroom closest to the panel
Answer: (b) At a readily accessible location, outside the building or inside nearest the point of entrance
Explanation: NEC 230.70 requires the service disconnect to be readily accessible, either outside or inside nearest the point where the service conductors enter the building.
3. What is the minimum service disconnect rating for a one-family dwelling under NEC 230.79(C)?
a) 60 amperes
b) 100 amperes
c) 150 amperes
d) 200 amperes
Answer: (b) 100 amperes
Explanation: NEC 230.79(C) requires a minimum service disconnect rating of 100 amperes for a one-family dwelling, although most new homes use 200 amperes.
4. What is the purpose of the drip loop at the weatherhead?
a) To increase the voltage of the service
b) To let rainwater drip off the wire instead of running into the conduit
c) To measure the current in the service drop
d) To ground the service conductors
Answer: (b) To let rainwater drip off the wire instead of running into the conduit
Explanation: Each service-drop wire forms a drip loop below the connection point so water drips off instead of following the wire inside.
5. Why is it dangerous to work on the meter base or service conductors yourself?
a) Because the wires are too thin to handle
b) Because everything before the main disconnect stays live even when the panel breakers are off
c) Because the meter will stop recording energy use
d) Because the utility will charge extra for the visit
Answer: (b) Because everything before the main disconnect stays live even when the panel breakers are off
Explanation: The service entrance is live before the main breaker, so it cannot be switched off from inside the home and must be handled by the utility or a licensed electrician.
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