What is the grid? Explaining a modern engineering marvel

Our continent-wide electricity network delivers light, heat, and myriad creature comforts


It’s been called the “world’s largest machine.”

It’s an engineering feet of Herculean proportions, and it provides us with light, heat, and other modern creature comforts—24 hours a day, 365 days a year.

It’s known as “the grid,” and it’s a massive, complex network of transmission lines, generation facilities, and transformers across North America.

How does the electricity grid work? What makes it so reliable? How is its power generated?

Keep on scrolling to learn the answers!

Hoover Dam

Keeping us powered up

The electricity grid includes three distinct components, often hundreds or thousands of miles apart—generation, transmission and distribution.

  1. Electricity starts at a generation facility, which could be a natural gas- or coal-burning power plant, a wind farm, a solar facility, a hydroelectric dam, or a nuclear power plant.
  2. Transmission lines carry high-voltage electricity over long distances. Transmission substations convert power from generation plants to extremely high voltages using “step-up” transformers.
  3. Local distribution networks take it from there, moving power from transmission lines to homes and businesses. So-called “step-down” transformers convert electricity back to lower voltages—allowing electricity to enter your home, where it runs your dishwasher, cooks your meals, powers your stereo, washes and dries your clothes, and brings light to a darkened room.

You’ve probably heard of the “electricity rush hour.” Daily household activities create a variable usage, or “load,” on the electricity grid—and that’s what makes the management of the grid so critical.

Going with the flow

Across the continent, there are three major interconnections that link up local or regional electricity grids and move power back and forth.

The Eastern Interconnection covers the region east of the Rocky Mountains; the Western Interconnection ranges west from the Rockies to the Pacific Ocean; and the Electric Reliability Council of Texas (ERCOT) encompasses most of the Lone Star State.

This network structure, which includes 35 separate links between Canada and the U.S., is essential. It offers multiple avenues for the flow of electricity, and links up generators with faraway consumer demand (areas called “load centers”)—all of which prevents power outages.

North America at night
Transmission tower repair

A fine balancing act

For the grid to work, it needs to be stable. In other words, electricity supply must match electricity demand—everywhere, all the time.

That’s the responsibility of balancing authorities, usually local or regional electric utilities. These authorities are constantly appraising expected power demand at any given time, making sure that enough supply is available to cover that demand, and managing the transfer of power with their counterparts in other sections of the grid.

If supply and balance fall out of balance, localized or widespread blackouts can occur.

Supply, meet demand

Power generation for the grid comes from various sources—wind, solar, power plants, hydroelectricity, nuclear—and all of these sources have their own personalities, so to speak.

Nuclear power plants and coal-fired electricity plants generally run at a steady level, and their output can’t be easily adjusted in the short term.

Natural gas-fired power plants, on the other hand, can be dialled up or down on a moment’s notice. That’s why these generators are used to meet sudden consumer demand peaks—for massive air conditioner usage in a heat wave, for example, or cranking thermostats during a cold snap.

Wind and solar are variable technologies, since the wind doesn’t always blow and the sun doesn’t always shine. They provide electricity whenever they are available—which presents a challenge for the grid, which must always be balanced.

That’s why natural gas, for example, is so important to the integration of renewable energy on the grid, since it solves solar and wind’s intermittency issues.

New York City at night

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