The Macrogrid: Building America's transmission backbone
Five ISOs have simultaneously approved the largest transmission expansion in U.S. history.
Combined with six major HVDC projects, the planned buildout would add 12,700 miles of
high-voltage line—a 13% expansion of the 345 kV+ network—at a cost
exceeding $100 billion.
12,700
New line-miles
345 kV and above
5,600
Miles at 765 kV
First new 765 kV in 40 years
2,800
Miles of HVDC
6 interregional projects
$107B
Total investment
Board-approved plans
Approved plans by ISO and project
345 kV
500 kV
765 kV
HVDC
How much the grid grows
The existing high-voltage grid (345 kV+) spans 98,000 miles. Approved plans add 12,700 miles—a 13%
increase. But 765 kV, which currently has only 2,410 miles, would more than triple to 8,000 miles.
HVDC would nearly double from 1,573 to 4,340 miles.
Existing
New (approved)
The land question: how much ROW does America need?
Today’s grid occupies 6.0 million acres of right-of-way—roughly the size of New Hampshire.
Approved ISO plans add just 320,000 acres, a 5% increase. But the DOE’s National Transmission
Planning Study (October 2024) envisions 2.4× to 3.5× today’s capacity by 2050.
That means millions of additional acres of new corridors. The DOE study doesn’t estimate
land use—we do.
6.0M
Existing ROW
422K miles, all voltages
+320K
Approved plans
+5.3% of existing ROW
+2.1M
DOE AC scenario
2.4× capacity — all 765 kV
+1.9M
DOE MT-HVDC
3.5× capacity — all HVDC
Adjust backbone technology assumptions
765 kV AC Backbone
1.0× — 1,951 MW
1,951 MW/corridor2.1M new acres
HVDC Backbone
±500 kV — 3,000 MW
3,000 MW/corridor1.9M new acres
Total U.S. transmission right-of-way by scenario
DOE National Transmission Planning Study — Executive Summary (October 2024)
147
TW-miles today (2020)
351
TW-mi — AC scenario
512
TW-mi — MT-HVDC
$270–490B
consumer savings through 2050
The DOE measures grid capacity in terawatt-miles but does not estimate right-of-way or land use.
ROW estimates above translate DOE capacity expansion ratios into acres using HIFLD-derived
ROW widths: AC scenario assumes 100% 765 kV (275 ft ROW, 17.1 ac/GW-mi),
MT-HVDC assumes 100% HVDC (150 ft ROW, 8.6 ac/GW-mi).
Benefit-to-cost ratio: 1.6–1.8×. Seam-crossing capacity expands from ~2 GW today
to 40+ GW under MT-HVDC.
Approved plans: MISO LRTP Tranche 1 & 2.1, ERCOT 765 kV STEP, PJM RTEP 2024,
SPP 2025 ITP, MISO-SPP JTIQ. HVDC projects: SunZia, TransWest Express, CHPE,
Grain Belt Express, SOO Green, Southern Spirit.
DOE scenarios: National Transmission Planning Study Executive Summary (Oct 2024),
Figures ES-3 through ES-5. ROW widths: EPRI, FERC siting guidelines.
Existing ROW: HIFLD transmission lines (52,244 features).
Capacity: SIL (AC), thermal (HVDC). DOE uses thermal ratings for all lines.
See also: Grid analysis | Interactive map.