Curated reference and analysis. Last full review: June 17, 2026
Verify all figures against ISO sources before relying on them for project decisions.
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U.S. ISO / RTO Large-Load Positioning
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Exhibit 2 · Project signal

Golden-to-Mars 500kV Transmission Loop

Transmission · Permitting
ISO/RTO:PJMConfidence:High
Status
Permitting
State
VA
County
Loudoun
Nearest city
Ashburn / Leesburg
ISO / RTO
PJM Interconnection
Utility
Dominion Energy / PJM
Developer / owner
Dominion Energy
Estimated load
Not disclosed
Estimated generation
Not disclosed
Reported capex (as cited)
~$513M reported (Golden-Mars segment)
Announced
2025
Expected COD
Targeted in service by June 1, 2028
Public summary
A 500- and 230-kV transmission loop around Loudoun County to serve the world's densest data-center cluster ('Data Center Alley'). The Golden-Mars segment is ~$513M; the broader Loudoun loop includes a 500kV, ~22-mile line feeding roughly 40 new substations (each ~100-300 MW). One of six new transmission lines Dominion is routing through Loudoun. Facing community petitions and SCC scrutiny over cost allocation.
Grid relevance
The clearest HV transmission and substation buildout driven purely by data-center load in PJM's Dominion zone, which PJM projects will see the largest absolute summer peak demand increase 2026-2030. Directly relevant to HV/MV EPC and substation construction work. Also a live example of the 'who pays' cost-allocation fight.
Last updated
2026-06-17
Sources
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