The grid is a complex web of infrastructure that moves electricity from where it’s generated to the places where it powers all the necessities of daily life. The grid, though, isn’t one homogenous thing: There are actually many grids across the United States (and the world) that rely on electricity generated by a variety of sources, mainly fossil fuels.
The U.S. power grid, called by some the largest machine in the world, is at the heart of the challenges related to a rapid shift to renewable energy. So what’s really going on among those hundreds of thousands of miles of high-voltage power lines and thousands of power plants? Let’s see what all those connections are about.
How does power travel through the grid?
In the United States, the grid is divided into three major regions: The Eastern Interconnection, which operates east of the Rocky Mountains; the Western Interconnection, which operates west from the Rocky Mountain states; and the Texas Interconnection. Within each of those systems are millions of miles of local electricity lines operated by a mix of private and public entities.
How does it all work? In the simplest terms, power generators, like a coal-fired plant or a field of wind turbines, generate electricity that’s sent through transmission lines linked to a swath of technologies that work to keep the lights on. These technologies include substations and transformers, which are responsible for taking the high-voltage current flowing through transmission lines and converting into the electricity that goes to customers.
Generation
There are many different kinds of electricity generators, but most rely on a behavior discovered by English scientist Michael Faraday in 1831. He found that moving a magnet inside of a coil of wires can induce an electric current flowing through those wires. What moves to generate that current can vary depending on the energy source going into the generator.
Most of the world and the U.S. get their power from turbine-driven generators, which center on blades mounted on a rotor. That rotor includes a series of insulated wire coils, and as the apparatus moves, the electric current flows through the generator. Those blades can be moved by the force of air (as in wind turbines) or steam (like in many fossil fuel–burning plants).
Solar relies on a different technology altogether. The photovoltaic cells on solar panels can convert sunlight directly into energy, which means they can be used to power small electronic devices like backyard lighting without the need for conversion. However, the amount of electricity that a single cell can provide is limited: For bigger purposes, like providing electricity to a home or the grid, photovoltaic cells need to connect to modules, or solar panels that include multiple cells.
There are also other types of generators, such as internal-combustion engines (like those that use diesel fuel), fuel cells, thermoelectric generators, and Stirling engines.
Transmission and conversion
Once the electricity is generated, it must either be stored or transmitted through power lines to customers. High-voltage electricity, typically above 1,000 volts in AC systems or 1,500 volts in DC systems, is the most efficient way to get electricity from the power plant to all across a region, and is carried by transmission lines.
Once electricity is generated and leaves the power plant, it travels along transmission lines to local substations with transformers that convert the energy to a lower, less dangerous voltage. Distribution lines then carry that electricity to houses and businesses, where additional transformers convert the electricity to even lower voltages, typically around 120V or 240V for residential use.
How does the grid handle changes in demand?
Costs for electricity tend to go up during times of peak demand—and also have a heftier carbon impact due to dependence on fossil fuel-powered peaker plants. You may have heard the phrase “beat the peak” without fully realizing exactly what the challenge means. The idea is to avoid using large amounts of electricity at the same time as your neighbors (such as the hottest, most AC-hungry hours of the summer), which in turn can help protect all of the various components of the grid, ensuring it doesn’t overload while also keeping prices down.
Fluctuating supply and demand on the grid is one of the biggest challenges for some renewable energy generators like solar and wind, which rely on the weather and therefore don’t produce electricity at the same steady rate. Solutions are in the works, however, as energy storage technologies continue to improve.
What can cause a grid to fail?
Ensuring the reliability of the grid is important not only to keep the lights on, but for people’s health and welfare. When any part of the grid system breaks down, it can lead to catastrophic failures for lifesaving equipment at hospitals and vital infrastructure. The worst-case scenarios can look like what happened in Texas in February 2021, when hundreds of people died in the aftermath of weather-driven power outages that left people without heat. Failures in America’s grids trace back to myriad issues, but most are linked to weather events, equipment failures, and demand.
Weather events
In recent decades, about 83% of the nation’s major power outages were blamed on weather-related events, according to Climate Central.1 Everything from hurricane-force winds to sunny-day flooding can pose threats to any part of a power grid’s infrastructure. Even solar storms can mess with the electromagnetic properties of some equipment. Events that can impact the grid include drought or water shortages, earthquakes, storm surge, ice storms, tornadoes, tsunamis, volcanic events, and wildfires.
Equipment malfunctions
While the easiest visual to imagine when you think of grid failure is downed power lines, any piece of the puzzle can cause an outage. While many equipment failures can be linked to extreme weather events (think flooding, strong winds, earthquakes, and even strong solar storms), in some cases the causes of faulty equipment trace back to aging infrastructure or even user error.
Cyber attacks
Cyber attacks—and even physical ones—on the grid are a real, if rare, threat. We still don’t know exactly how often these attacks occur, but cyber attacks can include the installation of malware that messes with electrical grid systems. Two such instances include a 2019 attack on an undisclosed utility in the Western US and a ransomware attack on the massive Colonial Pipeline in 2021. The response depends on the type of attack and what potential problems may arise with the system.
Human error
Accidents can also include errors in judgment. A downed tree, for example, could cause a small outage that can be exacerbated by operators’ decisions down the line, as was the case with the 2003 Northeast blackout that left an estimated 50 million people from New Jersey to Ontario without power.
What about microgrids?
“Microgrids” are just as they sound: Smaller versions of the more complex, centralized grid that can be used as back-up options or to provide power to a specific neighborhood or business complex. Microgrids can be used as standalone sources of power, or they can link back to the regular grid.
“I think [microgrids are] becoming a response to a fairly inflexible electric utility provision and regulations that are based on rules from 100 years ago that really don’t account for these kind of rapidly improving, small-scale, clean technologies like wind, and solar,” says Gregory Nemet, a professor of public affairs at the University of Wisconsin Madison, of American microgrid development. “I think microgrids could become a way for certain entities to kind of defect from the grid and have their own power system on a smaller scale.”
As of the start of 2023, there are 692 microgrids installed across the U.S. The DOE notes the expansion of microgrids can provide more resiliency for users because there can essentially be on and off switches between those localized sources of power and the grid at large.2 However, microgrids can come with high upfront price tags. A study by the agency’s National Renewable Energy Laboratory found that microgrids in the continental U.S. cost an average of $2 million to $5 million to get up and running.3 The Biden administration has offered some federal funding opportunities to offset those costs specifically for underserved and Indigenous communities.
Some interesting examples of microgrids are the Brooklyn Microgrid, the Stone Edge Farm Microgrid that powers a vineyard, spa, and guest homes, and the Santa Rita Jail Microgrid.
Are there other types of grids?
The well-established American grid is only one option available. The idea of autonomous grid models or relying on more high-voltage DC lines are in the works—but these often rely on technologies that still may be decades or more away from deployment.
Within America’s three main power grid regions are interconnected local electricity grids, much like the one that may be overseen by your local municipality or energy provider. That interconnection makes it a “centralized” grid, and in the U.S. there’s also a centralized market for electricity purchases that eventually trickles down to the consumer.
The National Renewable Energy Laboratory says it’s investing in the idea of a less centralized grid for the future. Decentralized grids can be attractive as localized solutions for electricity needs, as well as help manage intelligent energy devices and renewable energy sources. The futuristic vision is essentially of a self-driving power system that can detect problems and inefficiencies while balancing supply and demand back and forth between the source and users as needed (unlike our one-way power systems as we know them).
- Surging Weather-related Power Outages, Climate Central, Sep. 2022 ↩︎
- Microgrid Overview, U.S. Department of Energy, Jan. 2024 ↩︎
- Ibid ↩︎