800V DC vs 48V data centre power architecture
Two power distribution architectures at different levels of the data centre. 48V is the in-rack busbar standard (Layer 5); 800V DC is the facility-level bus (Layers 2-4) that feeds the 48V rack. The relevant comparison is between the LEGACY architecture (480V AC to 208V/415V to 48V) and the NEW architecture (800V DC to 48V direct). This is the choice.
01Bottom-line verdict
02Comparison table
| 800V DC (new) | 480V AC to 48V (legacy) | |
|---|---|---|
| Conversion stages | MV AC → 800V DC → 48V (2 stages) | MV AC → 480V AC → 208V/415V → 48V (3-4 stages) |
| End-to-end efficiency | ~95-96% (facility-to-48V-rack) | ~92-93% (facility-to-48V-rack) |
| Copper cost per MW | ~30% lower than 480V AC baseline | Baseline |
| Layer 2 equipment | Solid-state transformer (SST) | Traditional MV-to-LV transformer |
| Layer 4 architecture | Sidecar power rack (OCP Mt Diablo) | In-rack PSUs at bottom of IT rack |
| Standards maturity (2026) | OCP Mt. Diablo v0.7.0; IEC + UL extensions in progress | Mature, decades of NEC + UL coverage |
| Insurance underwriter comfort | Emerging (200 MW+ deployments now) | Fully mature |
| Skilled electrician availability | Emerging (training curriculum growing) | Universal |
| AI density supported | 100-500+ kW per rack | Effective up to ~50 kW per rack |
| Vendor supply base | SST vendors narrow (~7 global); rack ecosystem via OCP | Broad, mature, commoditised |
| Retrofit vs greenfield | Retrofit tax ~2x greenfield; greenfield preferred | Retrofit familiar |
03Decision framework
Choose 800V DC (new) when
- AI-density target ≥100 kW/rack. The economics + thermal envelope require 800V DC or equivalent
- Greenfield facility commissioning 2027+. Capex premium recovers via efficiency + copper savings in 3-4 years
- Hyperscaler-scale procurement. SST vendor supply sufficient at hyperscaler contract volumes
- OCP Mt Diablo ecosystem participation. Sidecar rack + power module supply chain now mature
- Skilled electrician availability confirmed. Regional workforce for DC-specific commissioning available
- Insurance underwriter has quoted the risk. Facility can be placed with insurers who accept 800V DC
Choose 480V AC to 48V (legacy) when
- Existing 480V AC facility with residual life ≥10 years. Retrofit tax exceeds incremental capex + Op savings
- Mid-cap operator without OCP procurement scale. Vendor supply + support may not be reliable at your volume
- Compute density below 40 kW/rack sustained. Legacy architecture still cost-competitive at that density
- Insurance market has not quoted 800V DC in your region. Regulatory + workforce ecosystem not yet at readiness
- Facility co-locates general-purpose compute (not AI). AI density economics do not apply
04Deep-dive research
05Primary sources
06Frequently asked
Is 48V being replaced?
No. 48V remains the in-rack busbar standard in both architectures. The 800V DC vs 480V AC question is at Layers 2-4 (perimeter conversion + building distribution + rack-level conversion) upstream of the 48V bus.
What is the payback period on 800V DC vs 480V AC for a new build?
Roughly 3-4 years for hyperscaler-scale AI-density facilities based on copper savings + efficiency gain. Longer for mid-cap operators without volume procurement.
Can I retrofit an existing 480V AC facility to 800V DC?
Technically yes, economically usually not. Supplement A decomposes the retrofit tax (roughly 2x greenfield). Practical alternative is hybrid retrofit for specific new AI-density zones within an existing facility.
Does 800V DC require different skilled electricians?
Yes. Different arc-fault behaviour, different protection regime, specific NFPA 70E arc-flash considerations. Workforce training curriculum expanding but regionally uneven as of 2026.
| Dimension | 48V DC (existing standard) | 800V DC (2026-2030 transition) |
|---|---|---|
| Rack power envelope | Practical up to 60-100 kW/rack | Practical to 500+ kW/rack (GB200 NVL72 tested) |
| Copper mass (busbar cross-section) | Baseline (heavy: 15-20 kg/m at 100 kW) | Roughly half (7-10 kg/m at equivalent power) |
| Distribution loss (facility to rack) | 2-4% end-to-end | 1-2% end-to-end |
| Conversion stages | AC → rack shelf → 48V → point-of-load | AC → 800V bus → rack shelf → point-of-load |
| Standards status (Aug 2026) | Mature: OCP Open Rack V3, industry-wide | Emerging: OCP Mount Diablo v0.5 (bipolar); Nvidia 800V (unipolar) |
| Vendor concentration | Diverse (Delta, Vertiv, Schneider, ABB) | Concentrated (Delta, Vicor, Vertiv leading design-in wins) |
| Retrofit feasibility | N/A (existing) | Feasible with bipolar (OCP Mount Diablo); difficult with unipolar |
| Best fit | Retrofit + colocation + inference workloads <60 kW/rack | AI training + hyperscaler greenfield above 100 kW/rack |