The Three Grids

There is no national electricity grid. There are three major interconnections: the Eastern, the Western, and then good ol' Texas runs its own (ERCOT). Only a few links tie East to West. Together these grids hold more than 12,000 utility-scale power plants serving 164 million customers.

The Linemen

Electric utilities restore power fast. After Hurricane Helene in September 2024, Duke Energy had restored more than 1.1 million of about 2 million Carolinas customers in less than 48 hours. Less than two weeks later, Hurricane Milton darkened about a million Duke customers in Florida, and 95 percent were back in about 96 hours. Crews replaced 1,640 poles and 1,350 transformers to do it.

The linemen behind those numbers worked 18-hour shifts in flood and debris, often at night, on lines that can kill them. OSHA data count 122 electrical deaths among power line installers and repairers in the previous decade. Still, they heroically climb.

Restoration of power is where this system works. Spare inventory of transformers is where it can fail.

The Transformers

A large electrical transformer is a tank full of specialized electrical steel, copper coils and oil that weighs as much as a locomotive. If one is destroyed, the factory can deliver a replacement in … wait for it … three years. You can hope that your utility keeps a spare around. Hope is not a plan. After all, electric utilities are a regulated monopoly sector that has little in the way of market discipline. They are centrally planned and most of their customers are captive.

Getting power from the generator to your house takes many transformers

In sequence, from the generator to the house:

Generating station and step-up substation. The generator makes power at roughly 13 to 25 kV. A step-up transformer at the plant raises it to transmission voltage.

Transmission substations and switching stations. These are the nodes of the high-voltage grid, at roughly 115 to 765 kV.

Bulk-power or intertie step-down substations bring voltage to the subtransmission level.

Distribution substations are the ones near your town. A transformer steps subtransmission voltage down to primary distribution voltage, commonly around 12 kV. Several outgoing feeders radiate from each.

Distribution transformers are the gray cans on poles and the green pad-mount boxes. They step primary voltage down to 120/240 volts for the service line to your meter.