Sites / Equinix Hertfordshire Campus (South Mimms)

Equinix Hertfordshire Campus (South Mimms)

Equinix · proposed (reported consented) · Hertsmere Borough Council

Hyperscale campus on an 85-acre green-belt site near M25 J23 at South Mimms, Hertfordshire (over 2 million sq ft). Originally promoted by DC01UK, which won outline planning permission from Hertsmere on 23 January 2025; the site was sold to Equinix in October 2025 and rebranded the Hertfordshire Campus. About 400 MVA reserved from National Grid; reported £3.9bn and about 250 MW. Construction reported from 2027, completion around 2030. Held at proposed until a lasting Hertsmere Public Access URL is linked; location pin is approximate.

Stated size

250 MW

biggest size stated for this site Operator

Source: Trade reporting: Equinix South Mimms about 250 MW campus

The largest megawatt figure on the public record for this one site (planning docs or operator materials). It may include stages that are not built yet. Not everyday electricity use; the source sits with the number. Stated size is not electricity use.

Site area

85 acres

farmland Operator

What was here: Land near M25 J23, South Mimms

Water

Not disclosed

No annual water figure in materials reviewed

Equivalences

No operator on this map discloses expected load factor (the share of peak power used on average), so yearly electricity figures are shown as a range, not as a known total.

83,333 kettles running at once
ⓘ Arithmetic and sources

83,333 kettles running at once (at biggest size stated for this site; power size, not annual use)
- Nameplate 250 MW treated as continuous power for a power-to-power comparison only.
- One kettle = 3 kW.
Figure type: biggest size stated for this site · stated
324,444-567,778 homes' annual electricity
ⓘ Arithmetic and sources

324,444-567,778 homes' annual electricity (at 40%-70% load factor)
- Uses biggest size stated for this site = 250 MW.
- Assumed average load = nameplate × 40%-70%.
- Home use = 2700 kilowatt-hours/year.
- No operator discloses load factor; this is a bound, not a measurement.
Local geography (load-factor range): about 1.5-2.7× Barking and Dagenham's annual electricity (the lowest-consumption local authority we compare against)
ⓘ Arithmetic and sources

At 40%-70% load factor: about 1.5-2.7× Barking and Dagenham's annual electricity (the lowest-consumption local authority we compare against) (annual electricity)

876-1,533 gigawatt-hours per year assumed
- Uses biggest size stated for this site = 250 MW.
- Energy = MW × 8760 h × load factor / 1000 → GWh/year.
- Compared to Department for Energy Security and Net Zero local-authority total metered electricity (all sectors).
- No operator discloses load factor; this is a bound, not a measurement.
Water: Water use: not disclosed
Site area: 48.3 football pitches

Claims on record

None recorded yet.

Disclosure checklist

Stated size (MW): disclosed
Water: not disclosed
Power usage effectiveness (PUE): not disclosed
Energy source claim: none on record
Load factor: not disclosed

Plain checklist, no aggregate score.

Right of reply

Right of reply: open; no response received. Email marco@prismaticlabs.ai. Subject is prefilled. Or see methodology.

Timeline

2025-01-23: DC01UK granted outline planning permission by Hertsmere Borough Council
2025-10: Site sold to Equinix (£3.9bn); rebranded the Hertfordshire Campus

Sources

No live planning application link recorded yet. We do not upgrade a site past “proposed” without one.

Map point: longitude -0.223, latitude 51.692. Last reviewed 2026-07-25.