Transmission tower seen on June 15, 2021 in Houston, Texas. The Electric Reliability Council of Texas (ERCOT), which controls about 90% of the power in Texas, has asked Texans to save power until Friday as temperatures rise in the state.

Brandon Bell | Getty Images

This story is part of CNBC’s “Transmission Troubles” series, a look at why the aging U.S. electric grid is struggling to keep up, how it’s improving and why it’s so important to fighting climate change.

The network of transmission lines that carry electricity across the United States is old and not set up to meet the expected demand for clean energy sources like wind and solar.

Currently, electricity production results in 32% of carbon dioxide emissions in the US, mostly from the burning of fossil fuels such as oil, coal and natural gas. These fuels are transported and burned where electricity is needed.

But cheap emission-free sources of energy, such as solar and wind, are only abundant in places where the sun shines or the wind blows, and that’s not necessarily close to homes and businesses. In addition, the demand for electricity will increase as fossil fuels are gradually replaced for a variety of other uses, such as electric vehicles and heat pumps.

Keeping the lights on and the air clean will require a lot of new transmission.

‘A double whammy’: Age and place

Why the US power grid has become unreliable

In 2021, the most recent year for which data is available, U.S. electric customers were without power for slightly longer than seven hours on average, according to data from the US Energy Information Administration. More than five of those seven hours were during what the EIA calls “major events,” including snowstorms, hurricanes and wildfires. That’s a significant increase from the three-to-four-hour average for outages between 2013 (the first year for which data is available) and 2016, with the main culprit being extreme weather.

“Extreme weather events such as the Dixie Wildfire, Hurricane Ida and the 2021 Texas Freeze have made it clear that America’s existing energy infrastructure will not withstand the continued effects of extreme weather events spurred by climate change.” said the US Department of Energy.

Transmission infrastructure lasts between 50 and 80 years, according to a 2021 presentation from the consulting firm, The Brattle group. Replacing aging transmission infrastructure is likely to cost an estimated $10 billion per year, according to the Brattle Group analysis.

American Electric Power, an energy company that owns 40,000 miles transfer mileshas said that 30% of its transmission lines will need to be replaced in the next 10 years, highlighted by a 2022 report from the transmission policy group, Grid Strategies.

In addition to the increasing age, the location of the existing transmission lines is a problem.

Fossil fuels such as oil, coal and natural gas are usually transported by rail or pipeline and then burned in power plants near cities.

The electric industry in the US grew up through a patchwork of local electric companies that met local demand, Rob Gramlichthe founder of Grid strategies, told CNBC. The system of transmission lines in the United States was built to serve that model of energy generation.

Clean energy sources, such as wind and solar, do not emit greenhouse gases, but the generated energy must be moved from where the wind and sun are strongest to where the electricity is actually used.

Wind resources in the United States, according to the National Renewable Energy Laboratory, a national laboratory of the US Department of Energy.

National Renewable Energy Laboratory, a national laboratory of the US Department of Energy.

That’s especially true for harnessing the highest quality of wind energy, the Princeton professor explained Jesse Jenkinsa macro-scale energy system engineer.

“Wind turbines scale with wind speed cubed. That means the best wind sites are eight times more productive than the worst, versus just twice as productive for solar, Jenkins says.

“The greater degree of variability in wind potential means we have to build wind farms where the wind really blows, and that tends not to be where too many people live! So wind development is a big driver of increased transmission needs,” Jenkins told CNBC.

It’s easier to build solar panels close to where they’re needed, but “not so for wind farms,” ​​Jenkins said.

The combination of an aging infrastructure in need of costly upgrades and an energy grid failing where clean — and cheap — forms of renewable energy exist is “unfortunately a double whammy for consumers,” Gramlich told CNBC.

“But consumers benefit from the low-cost generation that transmission enables,” Gramlich said. He advocates replacing old infrastructure with advanced technology that can handle next-generation transmission needs.

“It would be such a waste to replace old assets with replacements of the same capacity and quality,” Gramlich said.

Solar resources in the United States, according to the National Renewable Energy Laboratory, a national laboratory of the US Department of Energy.

National Renewable Energy Laboratory, a national laboratory of the US Department of Energy.

Demand will build quickly

In the 1960s and 1970s, electrical construction boomed in both the United States and Europe, said Constantine Staschuswho has focused on the issue of transmission throughout his career, both in California and Europe.

“Those were the times when California planned to have a nuclear power plant every 100 miles or so up and down the coast, many more than they actually ended up building, because they kept projecting 7% annual electricity demand growth, which they used to have in the 60s, into the indefinite future,” Staschus told CNBC. “And they thought they would need generation and transmission coming out of the ears to cover future demands.”

But during and after oil shocks in the 1970s, the US dramatically reduced its own energy demand. “Demand growth essentially dropped to 1 or 2% rather than seven and more or less stayed there,” he told CNBC.

From the late 1970s to the early 2000s, the U.S. transmission grid expanded about 2% per year, Jenkins told CNBC.

Now, demand for electricity will increase rapidly as efforts to respond to global warming and mitigate the effects of climate change increase.

Electricity demand in 2030 will be 14% to 19% higher than 2021 levels, according to an analysis by REPEAT (Rapid Energy Policy Evaluation and Analysis Toolkit), an energy policy project that Jenkins is part of leading, and 27% to 39% higher by 2035, Jenkins said.

“A 21st century grid must cope with a steadily increasing demand for electricity to power electric vehicles, heat pumps, industrial electrification and hydrogen electrolysis, and it must extend to new parts of the country to take advantage of the best wind and solar resources. Both factors mean that we simply needs a larger grid with more long-distance transmission,” Jenkins told CNBC.

“Build in the resiliency benefits of stronger interregional grid connections so that a region struggling with an extreme event can call its neighbors for help, and you have even more reason to build a stronger, larger grid,” Jenkins said.