How electricity reaches your home

TL;DR

Utilities use high voltage because it carries the same power with less current and less heat loss.
A transformer near the homes lowers that voltage to the 120/240 volts used by most U.S. houses.
One street can have overhead service on one side and buried service on the other.
One transformer can serve several homes because the homes do not all use their full electrical capacity at once.
A large 120/240-volt service can divide into two 200-amp paths. Each path carries L1, L2, and neutral, so both panels can supply 120-volt and 240-volt circuits.
The Tesla design shown here uses one Gateway and one Powerwall 3 on each path. During an outage, they form two separate backed-up systems.

Start with four measurements

Electricity needs a complete circuit. There must be a path to a device and a path back. When the path is complete, electrical energy can heat an oven, turn a motor, or light a bulb.

A water-pipe comparison is useful as a starting point:

Voltage is the push

Volts measure the electrical difference between two points. Think of water pressure. Voltage can be present even when no current is moving.

Current is the flow

Amps measure how much electric charge passes a point each second. A device draws current when it runs.

Power is the rate

Watts measure how quickly a device uses energy. A 1,500-watt heater uses energy faster than a 10-watt bulb.

kWh

Energy adds up over time

Kilowatt-hours measure total energy use. A 1-kilowatt device running for 2 hours uses 2 kWh.

For a simple load, these measurements are related:

wattspower

voltspush

ampscurrent

This relationship explains why power lines use high voltage. For the same power, higher voltage allows lower current. Lower current produces less heat in the wires, so power can travel farther with less loss.

What actually moves through the wire?

The wires already contain mobile electrons. With alternating current, those electrons mostly move back and forth. Electrical energy moves through the connected circuit very quickly. It is not a batch of electrons traveling all the way from a power plant to a toaster.

From the grid to a neighborhood

The grid is a connected system. It includes generators, transformers, transmission lines, substations, distribution lines, switches, fuses, and meters.

Generation

Power plants and other sources put energy onto the grid.

Transmission

Very high voltage carries large amounts of power over long distances.

Substation

Transformers lower the voltage for local distribution.

Distribution

Local feeders still operate at thousands of volts.

Home service

A nearby transformer supplies 120/240-volt service to homes.

Large lines on steel towers are usually transmission lines. The highest electric wires on ordinary wooden poles are usually distribution lines. Both normally operate far above household voltage.

Why are there often three high wires?

Many utility feeders use three-phase power. The system has three alternating voltages whose cycles are offset in time. This moves power smoothly and lets the utility spread customers across phases A, B, and C.

Three high wires on a pole may be the three phases, but appearance alone cannot confirm what a wire does. A typical detached house does not receive all three phases. Its transformer usually supplies single-phase, split-phase power instead.

Two routes through a neighborhood

Overhead and underground systems do the same jobs. One street can use both. Older homes on one side can receive overhead service while a newer group of eight homes on the other side receives buried service.

Older side: overhead

Distribution wires run on poles.
A transformer on a pole lowers the voltage.
A service drop runs through the air to the house.
The service connects to the meter and main panel.

The wire entering the house is on the low-voltage side of the transformer. It is not the same high-voltage wire at the top of the pole.

Newer side: underground

A protected branch leaves a distribution feeder.
An insulated primary cable assembly runs underground.
A transformer in a green cabinet lowers the voltage.
Buried service cables continue to home meters.

A gray riser on a pole protects the cable between the overhead line and the ground. The pipe itself does not carry electricity.

Overhead equipment is easier to see and reach, but it is exposed to trees, wind, ice, and vehicles. Underground equipment is protected from many of those hazards, but digging can damage it and repairs may take longer to locate. A pad-mounted transformer stays above ground so crews can reach it.

Illustration of a utility pole showing three primary phase conductors, a primary neutral, protection hardware, a riser, a streetlight, and communications lines. — A simplified transition pole. The vertical position of a wire is a clue, not proof of its purpose or safety.

An 8-home underground example

A single-phase branch can leave the overhead feeder, run down the pole, go underground to a pad-mounted transformer, then continue through buried service cables to eight homes.

1. FeederThe main route may carry all three utility phases along the street.
2. Tap and riserProtection hardware connects one phase and the primary neutral to an underground cable assembly. The assembly enters protective conduit.
3. TransformerThe green cabinet changes distribution voltage to residential 120/240 volts.
4. Home servicesBuried secondary cables and junctions connect the transformer to eight meters.

Simplified diagram of one phase and a primary neutral running underground from a utility pole to a pad-mounted transformer, followed by 120/240-volt service routes to eight homes. — One phase and the primary neutral feed the pad transformer. The transformer lowers the voltage before service cables reach the homes.

How can one primary branch serve eight houses?

The underground primary cable assembly carries a phase conductor and a neutral return path to the transformer. Some cable designs place neutral wires around the insulated phase conductor. The exact construction varies. Because this branch operates at high voltage, it can carry the same power with less current.

Suppose the eight homes together use 100,000 watts at one moment. This simplified comparison ignores losses and AC power factor:

On the 240 V secondary side

100,000 W ÷ 240 V ≈ 417 A

On an example 7,200 V primary

100,000 W ÷ 7,200 V ≈ 14 A

The 7,200-volt value shows the ratio. If voltage rises by 30 times, current for the same power falls to about one-thirtieth. Actual distribution voltage varies.

Utilities also account for load diversity. Eight homes do not use their full service capacity at the same time. A main breaker rating is a limit, not a measure of normal use. The utility sizes cables and transformers for expected simultaneous demand, engineering limits, and future growth.

What arrives inside a home

A typical U.S. home receives 120/240-volt, single-phase, three-wire service from a center-tapped transformer. The three wires are hot L1, neutral, and hot L2.

Swipe to follow the wires →

A center-tapped transformer supplies L1, neutral, and L2 through one meter to two 200-amp service disconnects. A feeder runs from each disconnect to a panel. Both panels can supply 120-volt and 240-volt circuits.

Hot L1 to neutral = 120 volts. Most lights and ordinary outlets use this.
Hot L2 to neutral = 120 volts. Other 120-volt circuits use this leg so the load can be balanced.
Hot L1 to hot L2 = 240 volts. An electric range, dryer, HVAC system, or EV charger may use both legs.
The equipment grounding conductor is a separate safety path inside the building. It normally carries no current.

What do two panels with 200-amp mains mean?

The service divides into two 200-amp paths, each ending at a panel protected by a 200-amp main breaker. Both paths carry L1, L2, and neutral, so each panel can supply 120-volt and 240-volt circuits.

People often call this a 400-amp service. A common version uses Class 320 metering, which is rated for 320 amps of continuous load, with two 200-amp main paths. It is not one 400-amp wire and not one path for each hot leg. Equipment labels give the exact ratings.

The names change at the first service disconnect. Conductors from the utility through the meter to that disconnect are service conductors. Conductors after the disconnect that supply a panel are feeders. A disconnect and panel can also be combined in one enclosure.

The homes in this 8-home example use this two-panel layout.

Normal utility power and Tesla backup

Without solar or batteries

Utility transformer Utility meter Service conductors divide into two 200 A paths

200 A service disconnect A Feeder A Panel A, 200 A main

200 A service disconnect B Feeder B Panel B, 200 A main

Service conductors run through the meter to two 200-amp service disconnects. After each disconnect, a feeder supplies its panel. Panel A and Panel B each receive L1, L2, and neutral. Some homes combine a disconnect and panel in one enclosure.

With solar, Powerwalls, and Gateways

The design adds one Tesla backup system to each 200-amp path:

One utility meter splits into two service paths. Each path has a Tesla Gateway 3 as its 200-amp service disconnect, followed by a feeder to a panel with a 200-amp main breaker. Each path also has a Powerwall 3 and solar strings. One path has a Powerwall expansion battery. — This design gives each panel its own backup path. The paths share the utility connection upstream, but each Gateway creates a separate backed-up system during an outage.

Each Gateway 3 is the 200-amp service disconnect for one path. A feeder runs from that Gateway to its panel. Each Powerwall 3 connects on the backed-up side of its Gateway and accepts DC power from its assigned solar strings. The design has two Powerwall 3 units plus one 13.5 kWh Expansion, for 40.5 kWh of nominal storage.

When the grid is working, utility power, solar power, and battery power can serve the panel on that path. Extra solar can charge its battery or flow to the grid when allowed.

When the grid fails, each Gateway opens its connection to the utility. Gateway A forms one backed-up island for Panel A. Gateway B forms another for Panel B. With enough sunlight and battery capacity, solar can power loads and recharge the battery on its own path.

The two backed-up sides do not combine. Powerwall A does not automatically power Panel B, and Powerwall B does not automatically power Panel A. This design keeps the two sides isolated, so it uses two Gateways and two Powerwall and solar paths.

Basic safety rules

Observe from a safe distance

Treat every overhead conductor, buried cable, transformer, pedestal, meter, and panel as energized unless the utility or a qualified electrician has made it safe. A wire's size, height, covering, or position cannot prove that it is harmless.

Stay at least 10 feet from overhead power lines. Higher-voltage lines can require more distance.
Never open, climb, sit on, or block a pad-mounted transformer.
In the United States, contact 811 before digging and follow your state’s waiting and marking rules. Public utility marking may not include privately owned lines after a meter.
Stay away from a fallen wire and anything it touches. Call 911 and the local electric utility.
Do not open electrical equipment to learn how it works. Ask a licensed electrician to verify a home’s service.

Check your understanding

1. Which measurement is most like pressure in the water comparison? Amps Voltage Kilowatt-hours

2. Why does the utility use high voltage before a neighborhood transformer? It creates extra energy It carries the same power with less current It makes electricity move more slowly

3. What is the main job of a green pad-mounted transformer? Store electricity like a battery Distribute internet service Change distribution voltage to home voltage

4. Can one street use both overhead and underground service? No, every home on a street must use the same route Yes, different groups of homes can use different routes Only if the homes use different household voltages

5. How does a typical home get 240 volts? From neutral alone Between hot L1 and hot L2 By receiving all three utility phases

6. What can each 200-amp path supply? Only one 120-volt hot leg Both 120-volt and 240-volt circuits A constant 200 amps

7. What happens to the two Tesla paths during a grid outage? They combine into one 400-amp backup system Each Gateway forms a separate backed-up island Both solar systems must remain off

8. What should you do before digging near underground service? Dig slowly and look for a cable Contact 811 and follow the local marking process Open the transformer and trace the cable

Sources

Equipment varies. Use utility records, equipment labels, and a licensed electrician to confirm a specific installation.