01 — MethodologyHow to read these numbersThe figures on this page come from planning-level cost guides and real project filings, not from a single national average — because a single average would hide more than it reveals. The core benchmarks are drawn from MISO's Transmission Cost Estimation Guide for MTEP24 (May 2024, priced in 2023 dollars) and its MTEP25 update (June 2025, escalated to 2025 dollars), CAISO's 2023-2024 Transmission Plan (May 2024), ERCOT's board-approved 765kV STEP backbone filings (December 2025), and utility rate-case and FERC Form 1 records from Arizona Public Service and the Wisconsin Public Service Commission.Where these sources disagree — and they often do, by a factor of two or more for the same nominal voltage class — this page shows the range rather than picking a winner. A 345kV single-circuit line, for example, prices out between $3.1 million and $3.8 million per mile across three MISO-region states in the same 2023-dollar study; a 765kV line in Texas prices between $7.1 million and $8.5 million per mile depending on the specific segment. Terrain, circuit count, structure type (steel lattice versus monopole), right-of-way acquisition, and state-specific labor markets explain most of that spread.All figures are rounded to one or two significant digits and labeled with their cost-year basis where the source specifies one. None of this is iRecruit placement data, bid data, or a quote — it is a synthesis of public planning documents and regulatory filings, current as of the August 2026 retrieval date noted in the source list below each section.What these figures are — and are notThese are market-level planning estimates compiled from public ISO cost-estimation guides, transmission-plan filings, and utility rate cases — not iRecruit data, not a bid, and not a substitute for a project-specific engineering estimate. Every figure is rounded and traceable to a named source. Where sources disagree on the same voltage class, both ends of the range are shown rather than averaged away, because the disagreement itself is informative: it reflects real differences in terrain, circuit count, structure type, and regional labor and right-of-way costs that any owner budgeting a real line will also face.02 — At a glanceThe benchmarks at a glanceThe whole guide in one screen. Each row jumps to the full section.0169-138kV distribution-adjacent$0.3M-$1.5M per mile overhead; underground runs 4-14x higher (Wisconsin PSC, APS FERC Form 1)$0.3-1.5M02230kV backbone$1M-$4.3M per mile overhead depending on terrain and circuit count (APS filing, WECC/TEPPC)$1-4.3M03345kV workhorse$3.1M-$3.8M per mile single circuit across three states, 2023$ (MISO MTEP24)$3.1-3.8M04500-765kV extra-high-voltage$7M-$10M per mile across CAISO's mountainous 500kV route and ERCOT's 765kV Texas backbone$7-10M05Undergrounding & urban routing4-14x the equivalent overhead cost per mile, worst in dense urban corridors4-14xThree anchor figures worth remembering: $3.5 million per mile is a reasonable rural 345kV single-circuit midpoint, $8 million per mile is roughly what Texas is paying for new 765kV backbone, and 4-14x is the undergrounding penalty an owner should budget for any urban segment of either.
03 — BenchmarksCost per mile by voltage classThe ranges below are overhead, steel-structure line costs unless noted otherwise. Each is anchored to a specific public filing rather than a rule-of-thumb, and the source is named in the card so you can trace it back.$0.3-0.8M/mi69kV single circuitWisconsin PSC's 2011 cost study (still the commission's standard reference, unescalated for inflation since) priced new 69kV overhead near $285,000/mile; Arizona Public Service's 2023 FERC Form 1 shows a $345,000/mile weighted average across 2,405 miles of 69kV overhead line.$0.4-1.5M/mi138kV single circuitUtility filings put flat-terrain 138kV overhead near $390,000/mile; MISO and WECC/TEPPC cost-estimation methodology pushes double-circuit or hill-terrain 138kV projects toward $1.0-1.5 million/mile.$1-4.3M/mi230kV single/double circuitArizona Public Service's 2022 230kV overhead estimate reached $4.3 million/mile; lower-terrain, single-circuit 230kV projects in utility rate-case filings run closer to $1-2 million/mile.$3.1-3.8M/mi345kV single circuitMISO's MTEP24 Transmission Cost Estimation Guide (2023$) prices three 100-mile 345kV single-circuit examples at $3.12M/mile (North Dakota), $3.45M/mile (Minnesota), and $3.76M/mile (Texas).$7-10M/mi500kV single circuit (AC)CAISO's 2023-2024 Transmission Plan prices the ~140-mile Humboldt-to-Fern Road 500kV single-circuit AC line — which crosses the mountainous Coast Range rather than flat terrain — at $980 million-$1.4 billion, or roughly $7-10 million/mile.$7.1-8.5M/mi765kV single circuitERCOT's board-approved 765kV STEP backbone segments price at $7.1 million/mile (Drill Hole-Sand Lake-Solstice, 104 miles) to $8.5 million/mile (Eastern Backbone, 1,109 miles), 2025 dollars.Sources: MISO Transmission Cost Estimation Guide for MTEP24 (May 2024, 2023$) and MTEP25 (June 2025, 2025$); CAISO 2023-2024 Transmission Plan (May 2024); ERCOT 765kV STEP backbone board filings (Dec 2025); Arizona Public Service FERC Form 1 (2023) and 230kV project estimate (2022); Wisconsin Public Service Commission 2011 cost study (still the commission's standard reference). Retrieved Aug 2026.Why the range is wide, not sloppyThe same voltage class can price two to three times apart because voltage alone is only one input. Circuit count, structure type, foundation depth, access-road mileage, and state-specific labor and right-of-way costs move independently of voltage — a flat-terrain single-circuit 345kV line in North Dakota and an urban-adjacent double-circuit 345kV line in a congested corridor are engineering cousins, not the same project priced two different ways. 04 — Cost driversWhat moves the numberSix factors explain most of the spread between the low and high end of any voltage-class range, and most of the year-over-year escalation since 2023.4-14xUndergrounding vs. overheadBurying a line instead of stringing it overhead multiplies cost roughly 4x in easy soil and 10-14x in dense urban corridors, per Wisconsin PSC filings and engineering-industry cost surveys.1.0-2.25xTerrain, flat to forestedWECC/TEPPC's transmission cost-estimation methodology applies a 1.75x multiplier for mountain terrain above 8% slope and 2.25x for forested corridors, against a 1.0x flat/scrub baseline.+45%Copper and aluminum conductorLME copper hit record highs near $14,500/metric ton in August 2026, up roughly 45% year-on-year; aluminum, the dominant conductor metal, has climbed alongside it, per Gordian and LME price data.+22%Utility transmission capex growthEEI-member investor-owned utilities project $39.9 billion in 2025 transmission spending, up about 22% from a record $32.6 billion in 2024, itself up from $30.0 billion in 2023.~5 yrsInterconnection queue delayThe median generation project reaching commercial operation in 2023 waited about five years in interconnection queues, versus under two years for 2000-2007 projects, per LBNL's Queued Up 2025 edition.89%Skilled-labor scarcity89% of transmission, distribution, and storage construction employers reported at least some difficulty finding qualified workers, per DOE's 2025 U.S. Energy and Employment Report.Stack the extremes and the range on this page compresses to a single useful lesson: a rural, flat-terrain, single-circuit 345kV mile can run close to $3 million today, while an urban, double-circuit, underground equivalent can clear $30 million — and conductor prices, capex competition, and crew scarcity are pushing both ends up at once, not just one. 05 — VariationTerrain and regional variationWECC's Capital Costs for Transmission and Substations methodology — used across TEPPC planning studies — assigns a terrain multiplier against a flat/scrub baseline. It is the most explicit, citable terrain-cost table in public use.Flat / scrub (baseline)1.0xWECC/TEPPC's reference terrain; every other multiplier below is expressed against this baseline.Desert1.05xMinimal clearing keeps desert routing close to the flat-terrain baseline, per WECC/TEPPC.Wetland1.2xSpecialized foundations and permitting for wetland crossings add about 20% versus flat terrain.Rolling hills (2-8% slope)1.4xGrading, access roads, and foundation work add roughly 40% versus flat terrain, per WECC/TEPPC.Mountain (>8% slope)1.75xSteeper foundations, helicopter structure sets, and longer access roads push cost to about 1.75x flat terrain.Forested corridor2.25xClearing and ongoing vegetation-management right-of-way work make forest the most expensive overland terrain category.Dense urban and suburban corridors do not usually get a simple terrain multiplier — they get pushed into undergrounding requirements instead, which is why the 4-14x undergrounding premium matters more to an owner's route selection than any single terrain factor. State-level labor and right-of-way markets shift the baseline further: MISO's own MTEP24 examples price the identical 345kV single-circuit design 20% apart between North Dakota and Texas. 06 — TrendHow costs have moved since 2023Every trend line points the same direction. EEI-member investor-owned utilities spent $30.0 billion on transmission in 2023, $32.6 billion in 2024 (a 13th consecutive record year for total utility capex), and are projected to spend $39.9 billion in 2025 — a roughly 22% single-year jump. CAISO's own Transmission Planning Process costs averaged $733 million per project from 2000-2022 but have averaged $6.64 billion per project since 2023, a roughly 9x increase, per the California Public Advocates Office's 2025 transmission dashboard.Meanwhile new high-voltage mileage has not kept pace: FERC data cited in Grid Strategies and Americans for a Clean Energy Grid's 2025 'Fewer New Miles' report show annual construction of 345kV-and-above lines falling from about 1,700 miles/year in 2010-2014 to roughly 535 miles/year in 2020-2024 — per FERC's corrected data in Grid Strategies and ACEG's 2025 addendum, which superseded the report's original ~345 mi/yr figure — with 888 miles built in 2024 alone (334 miles of 345kV, 554 miles of 500kV). Rising unit cost and falling volume together mean each new mile now carries a larger share of fixed planning, permitting, and interconnection-queue overhead than it did five years ago.Material input costs compound the trend: LME copper prices reached record levels near $14,500/metric ton in August 2026, and aluminum — the primary conductor metal on long overhead spans — has moved with it, per Gordian's copper price tracking and LME aluminum data. None of this is expected to reverse quickly; EEI's members are projecting $178 billion in transmission construction spending for 2025-2028 alone. 07 — WorkforceThe workforce side owners underweightEvery cost figure on this page assumes the crews to build the line are available on schedule, and that assumption is increasingly the weak link. The median annual wage for electrical power-line installers and repairers was $92,560 in May 2024, and BLS projects employment growing 7% from 2024-2034 with roughly 10,700 openings a year — most from retirements, not net growth, per the Occupational Outlook Handbook. Layered on top of the broader construction-labor market — Associated Builders and Contractors estimated the industry needed 439,000 additional workers in 2025 above normal hiring — the specialized craft pool for energized-environment transmission work (lineworkers, substation electricians, structure crews) is thinner still.DOE's 2025 U.S. Energy and Employment Report found 89% of transmission, distribution, and storage construction employers reported at least some difficulty finding qualified workers, with 59% of utility employers specifically citing difficulty hiring line workers in 2024. That scarcity shows up directly in the schedule risk behind this page's cost ranges: a project that can't staff its crews on the original timeline re-prices against a new, higher materials and capex baseline every quarter it slips, and a five-year interconnection queue (per LBNL) gives that scarcity years to compound before a single structure goes in the ground. Owners budgeting from these benchmarks should treat crew availability as a cost variable, not a scheduling footnote.For the hiring side of this market, see the Power & Grid Construction practice. 08 — FAQFrequently asked questions What does it cost to build a mile of transmission line in 2026?+It depends heavily on voltage and routing: public filings show roughly $0.3-0.8 million per mile for 69kV overhead up to $7-8.5 million per mile for 765kV overhead, per MISO, ERCOT, and utility rate-case filings cited above.Why is underground transmission so much more expensive than overhead?+Underground cable requires trenching or boring, specialized cable and thermal-management design, and denser permitting — typically 4x the overhead cost in easy conditions and 10-14x in dense urban corridors, per Wisconsin PSC filings and engineering-industry surveys.Which costs more per mile, 345kV or 500kV?+It depends on the project. MISO's 345kV single-circuit examples price at $3.1-3.8 million per mile, while CAISO's ~140-mile Humboldt-to-Fern Road 500kV single-circuit project — which crosses mountainous terrain — prices at roughly $7-10 million per mile. Terrain and circuit count matter more than the voltage step alone.How much has transmission construction cost increased since 2023?+EEI-member utilities' transmission capex rose from $30.0 billion (2023) to $32.6 billion (2024) to a projected $39.9 billion (2025), while CAISO's average per-project planning cost rose roughly 9x since 2023, per the California Public Advocates Office.Why do transmission project schedules keep slipping?+Two compounding constraints: a median five-year interconnection queue for projects reaching service, per LBNL's Queued Up 2025 edition, and a skilled-labor shortage — 89% of transmission and distribution construction employers reported hiring difficulty in DOE's 2025 U.S. Energy and Employment Report. Owner-side workforce intelligenceThe crews behind these benchmarks are as scarce as the copper. iRecruit is building its network of transmission and substation construction talent — project engineers, linemen and craft leadership — ahead of the build-out. Tell us what your program will need.Scope a search →Candidates — register with us →
