Rewiring the US—and the World

New Electricity Transmission Superhighway ‘Backbones’ Are Coming

By Jean Thilmany*

These three-abreast electrical transmission pylons in Webster, Texas, were built to transmit high-voltage alternating current, which has far more “line loss” over long distances than does high-voltage direct current. Jim Evans/Wikipedia

When you turn on your air conditioning on a hot summer day, it’s easy to forget the vast system of wires, turbines, transformers, substations, and control centers that deliver electricity capable of bringing cool air to you almost instantly. Because the process feels so effortless, it’s also easy to assume the power grid—the sprawling network that generates and delivers electricity—will always be there, largely unchanged.

But the way electricity is delivered across the United States needs major updating. For more than 100 years, generated electricity has flowed in one direction only: from power plant to consumer, with no lag in between. But today, with renewable energy sources contributing 22% of US electricity generation and the nationwide addition of rooftop solar and battery storage, electricity has to flow bidirectionally and intermittently. In many ways, that transformation has already begun, although it is still in its infancy.

Some experts describe the emerging system as a new kind of energy highway: a network of powerful high-voltage transmission lines capable of moving enormous amounts of electricity far more quickly and efficiently than ever before across vast distances.

In this diagram of an electric power system, the power plant (left) generates the electricity, which is stepped up to many thousands of volts. It travels through the transmission system (in blue), and is then stepped down by degrees to finally be available for homes and retail businesses. US Department of Energy

The need is becoming increasingly urgent. Rising electricity demand, the growth of artificial-intelligence (AI) data centers, the proliferation of electric vehicles always hungry for a charge, and the increasing electrification of homes and industries are all placing unprecedented strain on aging grids around the world.

In the US, where electric lines run 700,000 miles, “75% of the grid is over 25 years old” and in need of a makeover.

In the US, where electric lines run 700,000 miles, “75% of the grid is over 25 years old” and in need of a makeover, then-US Energy Secretary Jennifer Granholm said in a 2024 Heatmap podcast.

Bringing the System Up to Date

In such an environment, where a vast electrical network that is increasingly rundown and out of sync with the current energy landscape—major portions being 70 or 80 years old—an extensive overhaul is needed. According to Ed Myszka, chief executive officer at TRC, a consulting and engineering firm that helps companies design and transition their power systems, there is opportunity here. 

Indeed, “every so often,” Myszka writes on the TRC website, “an industry reaches an inflection point—one of those rare moments when change doesn’t just accelerate, it fundamentally redefines the path ahead. For the utility industry, 2026 is that moment.”

For more than a century, many traditional power plants sat within or relatively close to the cities they served. Today, however, much of America’s new energy comes from remote solar farms and offshore wind projects, many of which are in sparsely populated regions. That means electricity often must travel hundreds or even thousands of miles before reaching homes and businesses.

Trying to move all that power over older transmission systems can be inefficient. Energy is lost as heat during transmission—a problem known as “line loss.” The farther electricity travels through conventional alternating-current transmission systems, the more energy is lost along the way. 

Enter HVDC Transmission Technology

That challenge has pushed utilities, governments, and private developers to increasingly embrace a newer transmission technology known as high-voltage direct current (HVDC).

Transmission losses in HVDC lines are approximately 2% to 3% compared to 5% to 10% or higher in high-voltage alternating current (HVAC) systems. HVDC lines can also transport larger amounts of power more precisely and efficiently. Moreover, they can connect separate regional grids that do not operate in sync with one another, improving flexibility and resilience.

In its early days, the internet was called the “information superhighway” because it moved enormous amounts of information at unprecedented speed. Advocates of HVDC say the technology could become the electrical equivalent: an energy superhighway capable of transporting massive amounts of electricity more efficiently than much of today’s aging infrastructure.

According to a report by JPMorgan, HVDC projects can help modernize the grid by replacing aging infrastructure and improving the management of increasingly complex power systems.

Linemen in cherry pickers making repairs to electrical lines. American Public Power Association/Unsplash 

Traditional power systems primarily use HVAC. However, HVDC systems convert AC electricity into direct current (DC) for long-distance transmission and then convert it back to AC for everyday use in homes and businesses.

HVDC technology is particularly attractive for transmitting renewable energy over long distances.

HVDC technology is particularly attractive for transmitting renewable energy over long distances. Wind energy generated in Wyoming, for example, could be transmitted efficiently to California. Solar energy generated in the US Southwest could eventually help power Midwestern or Eastern cities.

HVDC Not a Silver Bullet

Still, experts caution that HVDC alone will not solve all of the grid’s problems. The US electrical system also needs upgraded local distribution networks, stronger substations and transformers, expanded energy storage, smarter grid-management software, and improved defenses against cyberattacks and extreme weather. Many utilities are also struggling with shortages of large transformers and long delays in permitting new transmission projects.

In other words, HVDC is increasingly viewed not as a replacement for the existing grid but as a high-capacity backbone layered on top of it—a network of electrical superhighways supplementing and strengthening local and regional systems.

The timing may be critical. According to the International Energy Agency, global electricity demand is expected to rise sharply—at an annual rate of 3.6%—over the next several years, driven in part by AI-related data centers, electrified transportation, air conditioning demand, and industrial growth. Data centers alone are expected to account for a significant share of new electricity consumption.

HVDC Globally

HVDC transmission is already being deployed in many parts of the world with large, dispersed populations, including China, India, Australia, and parts of Europe.

China, in particular, has become the global leader in ultra–high-voltage transmission.

According to Global Energy Monitor, China in particular has become the global leader in ultra–high-voltage transmission, building massive HVDC lines that move electricity thousands of miles from western hydroelectric, solar, and wind projects to eastern population centers. India is expanding HVDC infrastructure to connect renewable-energy projects across the subcontinent, while Europe increasingly relies on HVDC submarine cables to connect offshore wind farms and neighboring national grids.

High-voltage transmission towers taking electricity from a power plant to a faraway home TV or microwave. Radik 2707/Pexels

The United States has historically lagged behind, largely because of the high upfront costs and regulatory complexity involved in building long-distance transmission lines, says Bob Hobson, associate technical consultant at the engineering and construction firm Burns & McDonnell, writing in Utility Dive. Today, only approximately 1% of high-voltage lines in the US are HVDC.

But that is beginning to change. Today, a handful of US HVDC projects, many with names reminiscent of train lines, are in various stages of planning and construction. Among them is the North Plains Connector, a proposed 420-mile, 525-kilovolt HVDC line connecting Montana and North Dakota while linking major regional electricity markets. The TransWest Express project, meanwhile, is expected to carry Wyoming wind power more than 700 miles into Nevada, Arizona, and California.

Another major project, the 339-mile Champlain Hudson Power Express, is a mostly underground and underwater HVDC transmission line that will connect hydroelectric power from Quebec to New York City. Construction began in 2022, and the line is expected to begin operation soon.

The SOO Green Renewable Rail project plans to route underground HVDC cables largely along existing railroad corridors, connecting Iowa renewable-energy generation with Illinois electricity markets.

One major advantage of HVDC systems is their flexibility in routing. Unlike traditional overhead AC lines, HVDC cables can more easily be buried underground or placed underwater. Underground lines are less vulnerable to storms and can reduce visual impacts on communities and landscapes.

Underground HVDC lines may lower fire risks by eliminating the exposure of transmission lines and towers to high winds and vegetation tinderboxes.

Moreover, in wildfire-prone regions, underground HVDC lines may lower fire risks by eliminating the exposure of transmission lines and towers to high winds and vegetation tinderboxes.

Offshore wind development is another area where HVDC technology could become increasingly important.

In Europe, transmission operator TenneT has proposed large offshore HVDC hubs in the North Sea capable of linking multiple wind farms and the German and UK national grids. Similar systems may eventually play a major role in the US, as offshore wind development expands along sections of its 95,439 miles of shoreline.

Challenges to Upgrades Remain

Yet even as countries race to modernize their transmission systems, challenges remain.

Large transmission projects can take a decade or longer to be approved and to build. Environmental reviews, local opposition, land-rights disputes, supply-chain bottlenecks, and massive construction costs can all slow progress.

And while renewable energy receives much of the attention, grid modernization is increasingly being driven by broader concerns over reliability and national competitiveness. The rapid growth of AI, cloud computing, and electrified transportation is forcing governments and utilities to rethink whether current electrical systems can meet future demand.

In the future, when you turn on your air conditioner, you may have little idea where the electricity powering it originated. It could have traveled locally, or it could have originated hundreds or even thousands of miles away from a wind farm, hydroelectric facility, solar installation, or offshore energy project far from your city.

If today’s transmission plans move forward, electricity will likely travel farther, faster, and more efficiently than ever before—over a new generation of energy superhighways designed for a far more electrified world.

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*Jean Thilmany is a freelance writer living in St. Paul, Minnesota, who writes frequently about science and engineering topics.