Kimley-Horn to Loudoun: Data-Center Pipeline Implies ~8,190 MW — More Transmission Than PJM Had Approved

LOUDOUN COUNTY, Va. — A September 2024 due-diligence report Loudoun County commissioned from Kimley-Horn warns that the county’s own data-center site-plan pipeline would need far more high-voltage transmission than the transmission projects PJM had already approved for the mid-2020s — and it urges Loudoun to plan corridors, collocation, undergrounding, and reconductoring before more steel goes in the ground.

The Power Transmission Evaluation of Loudoun County, filed as Attachment 3 to county materials, inventoried parcels with active or pending site plans for data centers. Kimley-Horn counted roughly 148 pipeline parcels that could host about 117 buildings. Using an average of 70 megawatts per building — a planning assumption the consultants state plainly for hyper-scale campuses that can demand far more — the report puts pipeline electric need at approximately 8,190 MW if those buildings are built.

That figure sits against the forecasts that were driving regional planning at the time. Kimley-Horn notes PJM’s then-current outlook of roughly 5,700 MW of power growth through 2028 in the relevant window, while Dominion Energy had talked publicly about serving on the order of 8,346 MW of Loudoun data-center load by 2028, up sharply from the roughly 2,518 MW Dominion said it was already serving in the county. The consultants’ conclusion is blunt: if the site-plan pipeline builds out, Loudoun will need new transmission infrastructure beyond the PJM-approved project list summarized in the report.

That is not a theoretical mismatch. Loudoun sits inside Dominion’s PJM zone and hosts what Dominion itself has called the largest data-center market in the world, concentrated in a small footprint of Data Center Alley. PJM approval is only the first formal step for new high-voltage lines; Virginia’s State Corporation Commission still has to site and certificate projects. Every gap between pipeline megawatts and approved wires shows up later as new 230 kV and 500 kV proposals, substations, and easement fights that neighboring homeowners and farms absorb.

Kimley-Horn’s policy recommendations read like a checklist Democrats who control Loudoun’s Board of Supervisors and who have spent a decade recruiting hyperscale campuses now face in reverse. The firm tells the county to map preferred transmission corridors against planned data-center growth, redundancy, and reliability; to push collocation of new lines with existing infrastructure; to consider underground transmission inside existing overhead easements and on greenfield routes; and to pursue advanced reconductoring of lines already in the air before cutting new rights-of-way.

Behind-the-meter and campus co-location options appear in the same planning conversation because they are the only tools that shrink how much new bulk transmission has to cross residential Loudoun. The report’s arithmetic makes the political problem concrete for a Democrat-majority board that spent years treating data centers as by-right office uses and tax engines: 117 more buildings at 70 MW each is not a rounding error on a 5,700 MW regional growth case.

Dominion’s own public messaging has repeatedly tied Northern Virginia load growth to data centers, and Kimley-Horn cites Dominion open-house material projecting that Loudoun data-center load could more than triple by 2028. PJM’s 2022 RTEP Window 3 process, which selected a slate of 230 kV and 500 kV upgrades after dozens of competing proposals, is treated in the report as necessary but not sufficient if Loudoun’s pipeline is the demand case.

For ratepayers and for towns already staring at Aspen, Golden, Mars, Wishing Star, and the longer MARL and Valley Link corridors, the Kimley-Horn due diligence is a county-funded admission that land-use approvals and transmission planning have been out of sync. Democrat supervisors who green-lit by-right and legislative data-center growth created the 8,190 MW pipeline problem; the same board now owns the political choice between forcing more overhead steel through neighborhoods or insisting on undergrounding, reconductoring, and on-site power as conditions of further growth.

The September 2024 evaluation does not itself approve or deny any Dominion application at the SCC. It does give Loudoun residents a consultant-backed megawatt count to put beside every new 500 kV filing: if the buildings in the pipeline are real, the wires PJM had already blessed for the late 2020s are not enough — and the county’s own hired engineers said so in writing.

Email the Board of Supervisors at:
Phyllis J. Randall (Chair, At-Large) – Phyllis.Randall@loudoun.gov,
Michael R. Turner (Vice Chair, Ashburn District) – Mike.Turner@loudoun.gov,
Juli E. Briskman (Algonkian District) – Juli.Briskman@loudoun.gov,
Sylvia R. Glass (Broad Run District) – Sylvia.Glass@loudoun.gov,
Caleb Kershner (Catoctin District) – caleb.kershner@loudoun.gov,
Matthew F. Letourneau (Dulles District) – Matt.Letourneau@loudoun.gov,
Kristen C. Umstattd (Leesburg District) – Kristen.Umstattd@loudoun.gov,
Laura A. TeKrony (Little River District) – Laura.TeKrony@loudoun.gov,
Koran Saines (Sterling District) – Koran.Saines@loudoun.gov

Email the Loudoun County School Board:
April Chandler, april.chandler@lcps.org,
Anne Donohue, anne.donohue@lcps.org,
Deana Griffiths, deana.griffiths@lcps.org,
Ross Svenson, ross.stevenson@lcps.org,
Kari LaBell, kari.labell@lcps.org,
Jon Pepper, jonathon.pepper@lcps.org,
Lauren Shernoff, lauren.shernoff@lcps.org,
Sumera Rashid, sumera.rashid@lcps.org,
Amy Riccardi, amy.riccardi@lcps.org,