Holy Cross Energy has an ambitious goal: 100% renewable energy sources by 2030. It’s a tall order, complicated by the Colorado co-op’s mountainous service territory, which isn’t well-suited to wind or solar power generation.

But just 100 miles or so to the east of the co-op’s Glenwood Springs headquarters, Colorado’s Front Range and eastern plains offer ample wind resources. And the states to its south are among the nation’s solar power leaders.

It’s the lack of transmission that keeps the region’s renewable power from reaching the western part of the state, says Bryan Hannegan, Holy Cross Energy president and CEO.

“Our transmission access is our biggest worry” for meeting the 100% goal, he says.

Hannegan, who served as associate director at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) before joining Holy Cross, sees a solution in the creation of a “super grid.”

The concept, also known as the macro grid, entails uniting the nation’s regional transmission systems with high-voltage, direct-current (DC) interties. In particular, it would bridge the seam that runs along the Rocky Mountains between the western and eastern grids and would also tie ERCOT, the wind-rich Texas grid, into a national system.

“As we used to say at NREL all the time, the people are where the power isn’t,” Hannegan says. “And the power is being generated where the people aren’t.”

While at NREL, Hannegan oversaw a study that found a super grid could help reduce costs for consumers by allowing a “balancing of power supply over much larger regions,” he says, “allowing us to harness the resource diversity we have in this country.”

In particular, it would enable greater use of wind and solar power, says Tracy Warren, director of the Macro Grid Initiative at the American Council on Renewable Energy.

“Much of our vast renewable resources are located in remote regions far away from where the power is needed in population-dense areas,” she notes.

Being able to move solar and wind power to those areas could increase the utility of renewable generation. One scenario outlined in a study showed a hypothetical heat wave in August causing air conditioners to drive up demand. As the sun moved across the United States, solar plants in the West sent power eastward, limiting the need for expensive peak-load fossil-fuel generation. As the sun moved west and began to set, midwestern wind farms—today in the Eastern grid—sent power westward to relieve pressure on the coast’s coal- and gas-fired generation.

Worth the cost?

The price tag for building the DC transmission necessary to create a coast-to-coast super grid would be eye-popping: The NREL study estimated it could cost at least $80 billion, but it could return economic benefits of twice that amount.

“By every measure, a more interconnected grid delivered better outcomes—lower carbon emissions, lower cost to consumers, better reliability,” says Hannegan, along with job creation and other economic benefits in the parts of the country where more renewable energy generation would be built.

But a super grid would also face significant challenges.

“Any transmission beyond a local, minimal addition to an existing line is going to be met with huge amounts of opposition,” says NRECA Chief Engineer Paul McCurley. “Not just technical, geographic, economic, and environmental challenges but many not-in-my-backyard battles: ‘Why do I need to see this monumental, ugly thing when I’m not going to be getting any value out of it?’”

Patti Metro, senior grid operations and reliability director at NRECA, says DC interties and converter stations for the three alternating-current (AC) grids, which are not synchronous, would be complicated and expensive but would not require new technology.

Still, Metro points out that much of the recent focus in the industry has been on reducing, not expanding, the distance power travels, turning to more localized, distributed generation that integrates renewables sources like solar and tends to reduce the need for new transmission facilities.

“I feel like we’re heading in the other direction,” she says, “where you’re putting the generation where the load is.”

Another issue is the allocation of costs. Basin Electric, a G&T based in Bismarck, North Dakota, operates coal, gas, and wind generation to serve 140 member systems, including distribution co-ops and other G&Ts in nine states stretching from the Dakotas to New Mexico. As the demand for power grows, “new transmission development is probably going to be essential, and if there’s a transition to more renewable energy, that’s only going to add to the demand,” says Tom Christensen, Basin’s senior vice president for transmission.

But, he adds, the construction cost of a super grid raises concerns, even if it eventually saves money.

“Regardless of who funds it—banks, utilities, whoever—the point would be that ultimately, some set of retail customers will have to pay. It will show up in customer bills,” he says.

Rural, sparsely populated areas like the Great Plains, where wind generation is expanding, should not be asked to bear costs that exceed the benefits to their region if the transmission is largely carrying the power elsewhere, Christensen says.

He notes the super grid would require unprecedented coordination on a national scale to make sure the connections were cost effective, a task that’s generally handled by regional transmission organizations (RTOs).

“In general, when it’s transmission planned by an RTO, you really get a cost-effective solution, and you hopefully get an equitable distribution of cost to consumers,” he says, but a macro grid would cross RTOs, complicating planning.

He could see starting a buildout of regional grid interties on a smaller scale: “a more measured approach, going through the RTOs, trying to be very careful determining what’s economically justified.”

Warren acknowledges the macro grid will require large-scale planning but reiterates that transmission investments will pay dividends. She points to a study that shows increased transmission development at the “seams” between regions could save consumers up to $47 billion annually and return more than $2.50 for every dollar invested.

“We’re going to have to invest in transmission regardless,” she says. “Some 70 percent of transformers and transmission lines are more than 30 years old. Simply rebuilding this infrastructure is inefficient in light of a changing resource mix and electrification.”

One of the possibilities for siting the lines is to take advantage of existing rail and interstate highway rights-of-way, Warren notes. Burying lines is also an option, although more expensive.

She sees the macro grid working in concert with more localized generation to help the country reach the ambitious clean energy goals states are setting and the incoming Biden administration has promised to set on the national level.

Biden’s platform calls for moving the United States to a 100% clean energy economy, with net-zero carbon emissions, no later than 2050, a goal several states have also set.

To meet goals like those, “it’s all hands on deck,” Warren says. “It’s a large-scale challenge that demands a large-scale solution. When you look at the sheer volume of gigawatts of pollution-free power needed, you’re going to have to be able to access those big sources of renewable energy and move the power long distances. Through a macro grid, we can get there.”