US high-voltage electric transmission line additions totaled 552 miles (888km) in the first 11 months of 2022, less than half the previous year, and far below what the country will require each year to help achieve President Joe Biden’s goal of carbon-free power by 2035, according to a report by the Federal Energy Regulatory Commission (FERC).
About 73% of last year’s additions were comprised of 230kV or less lines with the balance almost entirely 345kV, the workhorse overhead high voltage conduit of choice used by utilities in the wind-rich Midwest and Texas for transferring power long distances.
The 345-360kV voltage class lines are also widely employed in the Western Interconnection, one of three that comprise the US grid, which covers 13 western states (and two Canadian provinces) and contains more than 1TW of untapped solar and wind resource.
Without significant expansion of the grid’s physical structure, accessing most of that resource will be difficult and likely slow the energy transition by denying consumers access to some potentially cheapest US onshore renewable power.
There is already a staggering 1TW of generation and 420GW of storage capacity seeking interconnection nationwide, most of it zero-carbon. The US had 1.26TW of installed generating capacity on 1 December, with about 450GW from emission-free sources.
Looking ahead, transmission developers expect to have 6,335 miles of proposed projects in service between last December and April 2025, FERC reported in its Energy Infrastructure Update for November 2022, citing data from a staff data base and consultant C Three Group.
Nevertheless, only 53%, or about 3,359 miles has “high probability of completion”, according to the report. This includes 1,345 miles of 230kV and lower voltage, 412 miles of 345kV, and 1,602kV of 500kV, which anchors the long-distance grid in Arizona, California, Montana, Oregon and Washington state.
If accurate, this would represent a modest improvement over 1,368 miles energised in 2021 and 897 miles in 2020, but a fraction of the up to 10,000 miles a year the country may need to fully clean its grid, according to the National Renewable Energy Laboratory.
Last month, the non-profit North American Electric Reliability Corporation, which developed and enforces mandatory grid reliability standards approved by FERC, issued data showing about 15,500 miles of transmission lines under construction or in planning for the 2022-31 horizon.
The primary driver for 14% was integration of renewable and variable resources, while 56% will strengthen grid reliability and 14% to ease congestion or for economic reasons, with the remaining 16% for other reasons.
More high-voltage lines would also allow regional grid operators to better cope with climate-spawned extreme weather that can force generators off-line – as occurred during the devastating 2021 freeze in Texas – by importing surplus solar and wind power from other regions.
Biden and clean energy industry groups remain hopeful that FERC can spearhead federal efforts to overcome transmission barriers focused on planning, permitting, and payment, with expectations a replacement will soon to named to replace Rich Glick, the clean-energy-friendly chairman whose term expired at the end of 2022.