Last week, Colorado energy regulators, who appeared astonished at the high costs, agreed to set aside a $2.82 billion request from Xcel Energy Colorado for new high-voltage transmission lines to serve the Denver metro and other areas.

In its 2021 electric resource and clean energy plan that’s before Colorado Public Utilities Commission, Xcel said it wants to build new transmission as part of a $15 billion investment to achieve an estimated 87% reduction in carbon emissions by 2030.

The request includes $2.14 billion for the Denver metro transmission network upgrades, $176 million for upgrades to the San Luis Valley network and $252 million for the May Valley-Longhorn extension.

Xcel’s latest version of its 2021 energy resource and clean power plan caught the energy regulators by surprise, noting the 850% increase in the costs from previous estimates.

“We’re seeing nearly nine times multiplication of what was anticipated in Phase One to be the cost of Denver metro transmission upgrades – a jarring almost $3 billion of new transmission upgrades in total,” PUC Commissioner Megan Gilman said at the hearing.

Commissioners Eric Blank and Tom Plant agreed with Gilman that parts of Xcel’s plans should be put on hold pending further proceedings.

“More transmission isn’t necessarily the solution to developing more clean energy,” said Jeremy Nichols, senior advocate for the Center for Biological Diversity’s Environmental Health Program. “I think it’s critical that the PUC really scrutinize whether Xcel is taking advantage of existing transmission opportunities, including distributed generation opportunities, and not just rubberstamp the company’s demands.”

“More transmission is a major investment and the last thing we want is for Xcel to saddle ratepayers with ineffective, inefficient, or worse environmentally destructive transmission projects,” Nichols said.

“We appreciate the discussion at the Commission and its verbal approval of elements of our proposed Clean Energy Plan,” said Xcel spokesperson Michelle Aguayo in a statement. “While the approved plan increases renewable energy to 77% of our energy portfolio by 2030, our updated preferred plan offers greater benefits for customers by adding more renewables (83% of our energy portfolio by 2030), capturing more federal tax dollars, reducing more carbon emissions over time and is better for our union coworkers.”

Xcel Energy has already been granted permission by the PUC to build about 550 miles of new transmission lines in eastern Colorado at a cost to ratepayers of $1.7 billion.

“Existing transmission on the eastern plains is nearly full and the addition of this additional transmission capacity is needed so that we can add more renewable energy to the grid,” said Robert Kenney, president of Xcel Energy Colorado, at the kickoff of its “Power Pathway” project in August. “The pathway will provide our high voltage backbone transmission and it will allow us to connect and unlock over 5,000 megawatts of new renewable energy produced right here in the eastern Colorado.”

Kenney said that Xcel has already received an “unprecedented” nearly 1,100 bids for new energy generation and storage.

The proposed projects, Kenney said, span across the state, with a concentration of those proposals located along Colorado’s power pathway transmission corridor.

Neither Xcel nor Colorado is alone in facing problems with connecting renewable energy sources to the grid.

Costs for high voltage direct current lines can cost $1.17 million to $8.62 million per mile, according to the federal Energy Information Administration.

As of September, a 330-mile transmission line extension in New York is projected to cost $6 billion, and more than 10 other transmission projects are underway nationally as well, according to Statista.

Aguayo told The Denver Gazette in August that the $1.7 billion Power Pathway project costs $2.44 million per mile, not including land purchases or substation costs.

Another problem, experts have said, is the sheer scale and time needed to build so many miles of transmission lines.

Energy author Robert Bryce wrote that, from 2008 to 2021, the U.S. high-voltage transmission system grew by about 1,700 miles per year.

“Thus, at current rates of growth, doubling the size of America’s high-voltage transmission grid will take about 140 years!” Bryce said. 

The Federal Energy Regulatory Commission has been warning of grid reliability issues related to the premature closure of fossil fuel power plants and imprudent dependence on intermittent renewables, as well as problems and delays in connecting new generating sources to the grid going back to 2022.

“The United States must focus on power reliability as it transitions away from fossil fuels to cleaner energy sources,” said Willie Phillips, acting chairman of the Federal Energy Regulatory Commission at a District of Columbia Clean Energy Summit in January.

Electric power transmission, which the federal commission has identified as a top area hindering the energy transition, will be key to stabilizing the grid, said Phillips.

Phillips referred to widespread power outages suffered during 2022 winter Storm Elliott, when the grid failed in almost two-thirds of the U.S., as one of the most recent examples of the vulnerabilities of a grid facing increased demand amid the shift toward renewable energy.

A report by Princeton University studied five technological pathways to net zero carbon electricity using existing technologies that could theoretically decarbonize the entire U.S. economy.

In the report’s highest electrification scenario – which it stated would supply nearly full electrification of buildings and transportation – Net-Zero America co-principal investigator Jesse Jenkins told The Denver Gazette in an email that, in order to get there, the U.S. would have to increase transmission capacity by nearly 300%. Jenkins is an assistant professor and energy systems engineer at Princeton. 

“Reaching the goal of net-zero greenhouse gas emissions by 2050 will require substantial investment in the U.S. transmission grid,” Jenkins said. “One scenario included in the Princeton Net-Zero America study identified a need for about 60% more transmission capacity by 2030 and tripling current capacity by 2050.”

This could mean building as much as 884,000 miles of new transmission lines nationwide to add to the existing 183,000 miles of lines, at a potential cost of $3.6 trillion, according to the report.