Start with the load, not the voltage. Define rack peak power, growth, utility capacity, availability target, existing distribution and available space. Then choose among three routes. The first is the conventional AC path with rack-level conversion. The second is an AC-fed 800 VDC power rack or “sidecar” for retrofits. The third is medium-voltage AC converted directly to an 800 VDC backbone in a new facility. Higher-voltage DC cuts current and can remove conversion stages. The size of the saving depends on the architecture and the site, and the headline figures in circulation come from vendors. Redundancy, protection, monitoring, maintenance and cooling have to be designed together with the topology.
This guide covers how to make that choice, what to specify at each boundary, and which claims to treat as forecasts rather than facts. It draws on NVIDIA’s 800 VDC publications and DGX SuperPOD documentation, Open Compute Project (OCP) material and a Renesas white paper. It does not replace a site-specific engineering study under your local electrical code.
What you need to know before comparing topologies
No architecture can be judged without these inputs. Each one changes which option is viable, so collect them first.
- Rack load profile: steady-state peak, transient behavior, and the growth envelope. Racks are described as ranging from around 100 kW to over 1 MW in NVIDIA’s 800 VDC material, and Renesas describes racks reaching several hundred kilowatts.
- Compute platform requirements: input voltage, connector and busway interface, and the vendor’s own redundancy guidance.
- Utility service: service voltage, available capacity and interconnection constraints.
- Existing distribution: spare AC capacity upstream, UPS topology, busway or cable routes, and floor or row space for conversion hardware.
- Availability and recovery objectives: what happens to a job when a rack or a power path fails, and whether jobs can resume from checkpoints.
- Cooling and space: power conversion equipment produces heat and takes up floor area, so it competes with compute for both.
- Jurisdiction: the electrical code, inspection regime and permitted DC distribution practices at the site.
The three power architecture paths
| Option | What it does | When to investigate it | Main comparison axes |
|---|---|---|---|
| Conventional facility AC, rack conversion | Delivers AC through the facility and converts it at or near the IT rack to low-voltage DC | Existing sites and racks whose loads fit their present distribution | Compatibility with existing plant, number of conversion stages, rack space, conductor current, fault domains, UPS topology |
| AC-fed 800 VDC power rack / sidecar | Converts existing 480 VAC near the row and distributes 800 VDC to compute racks | Retrofits where upstream AC capacity and row space exist | Retrofit disruption, local conversion hardware, busway and connector interface, protection, maintainability, confirmed availability |
| Direct MVAC-to-800 VDC | Converts medium-voltage AC to an 800 VDC backbone at facility scale | New facilities designed around DC distribution and high-density modular blocks | Utility and interconnection design, conversion and fault-protection design, battery energy storage (BESS) or DC UPS integration, code and operational readiness |
Conventional AC with rack-level conversion
This is the baseline. AC runs through the facility and is converted to low-voltage DC (54 V in the rack-level systems NVIDIA compares against) at the IT rack. It works while rack power fits what the existing busway, PDUs and circuits can carry. As rack power climbs, current at low voltage grows in proportion, and so do conductor cross-section and the space spent on busbars and cabling inside the rack.
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AC-fed 800 VDC power rack or sidecar
OCP describes the side-rack route as local conversion from existing 480 VAC to either ±400 VDC or 0–800 VDC. The facility’s upstream AC stays as it is. The conversion moves into a dedicated power rack beside the compute racks, and 800 VDC runs from there to them. NVIDIA’s 2026 announcement lists an MGX-compatible 800 VDC power rack for the second half of 2026 and a row power center for 2027, supporting up to 2 MW per row.
This option suits a hall where upstream AC has headroom but the distribution after it does not. Its costs are floor space for the power racks and a new DC protection and maintenance regime within the row.
Direct medium-voltage AC to an 800 VDC backbone
For a greenfield site, OCP describes converting MVAC straight to a facility-wide DC backbone. NVIDIA’s technical material describes the same idea: a more direct grid-to-800 VDC path, row busways, and DC-DC conversion inside the compute rack to feed lower-voltage equipment. OCP’s description of backbone options includes BESS integration and DC UPS functionality. This route removes the most intermediate AC stages but depends most heavily on protection devices and operating procedures that are still being standardized.
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Why voltage matters: the current arithmetic
Current for a given power falls as voltage rises. The figures below are illustrative arithmetic only, ignoring losses and power factor. For three-phase AC they use line-to-line voltage with unity power factor.
| Rack power | At 54 VDC | At 480 VAC, three-phase | At 800 VDC |
|---|---|---|---|
| 100 kW | about 1,850 A | about 120 A | 125 A |
| 1 MW | about 18,500 A | about 1,200 A | 1,250 A |
Two things follow. First, 54 V distribution at megawatt scale is impractical, which is why higher-voltage distribution to the rack is the main driver. Second, 800 VDC does not reduce current compared with 480 VAC on a line-current basis. The advantage over AC comes from needing two conductors rather than three or more, fewer conversion stages, and no AC-specific equipment in the rack path. So when someone quotes a copper or efficiency saving, ask which baseline it was measured against.
What the vendor claims do and do not establish
- NVIDIA’s architecture claim: NVIDIA says 800 VDC reduces conversion and routing volumes and significantly reduces current, copper use and cable bulk compared with rack-level 54 VDC and facility-level 480 VAC systems. It also says this can fit more compute into a footprint. These are vendor claims about the architecture, not independently demonstrated savings at every site.
- NVIDIA’s numbers: In its 2025 technical blog, NVIDIA reports up to a 5% end-to-end efficiency improvement and 45% lower copper requirements in its own comparison. It says the architecture can scale from 100 kW to over 1 MW racks. Treat “up to 5%” as a potential benefit that depends on comparison and design assumptions.
- Renesas’s converter figure: Renesas’s October 2025 white paper describes an isolated 800-to-48 V DC-DC stage as one way to keep much of the existing 48 V ecosystem. It cites 98% efficiency for a specific LLC DCX converter topology. That is a single-stage figure and not whole-facility efficiency.
- What is missing: No independent deployment study or neutral field-measured efficiency result was available for this article. Use the figures to compare options, then model your own site.
Two details matter when you read the Renesas material. One is that an 800 V to 48 V stage in the compute rack is a legitimate design choice and not a failure of the 800 VDC idea. It lets compute trays that expect 48 V or 54 V keep working. The other is that the architecture still has conversion stages, just fewer and in different places.
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Which path fits your site
- Does the existing distribution carry the planned rack power with margin? If yes, and the growth plan stays inside that margin, conventional AC with rack conversion remains valid and avoids new DC protection practice.
- If not, is upstream 480 VAC capacity available and is there row space? If yes, evaluate an AC-fed 800 VDC power rack or sidecar. Confirm that the compute platform accepts 800 VDC and that the product is orderable and certified where you are.
- Is the facility new, with an MV utility connection and a long planning horizon? Evaluate a direct MVAC-to-800 VDC backbone, with BESS or DC UPS integration in scope from the start.
- Is the compute platform’s roadmap tied to a voltage? If the platform you will buy in two to three years takes 800 VDC, a conventional design may need a second rebuild. Weigh that against the maturity risk of early DC equipment.
OCP’s guidance is that there is no single prescriptive 800 VDC design. The goal of its work is common interfaces and requirements that keep flexibility across real deployments. Google’s Tom Garvens, quoted by OCP, said common 800 VDC interfaces can help scale AI infrastructure “while protecting the flexibility operators need in real deployments.” Design to the interface, not to one vendor’s whole stack, where you can.
How to design the power chain, step by step
- Set the load envelope. Record steady peak, transient swings and a growth case per rack and per row. Size to the growth case, not the day-one load, wherever the infrastructure is hard to change later, such as busways, transformers and conduit.
- Define the facility block. Decide the unit that repeats: a rack, a row, or a hall-scale module. NVIDIA’s roadmap puts the row at up to 2 MW for the planned row power center, so the row is a natural block for AC-fed designs.
- Choose the path. Use the decision steps above. Write down the reasons, since the choice constrains cooling, space and procurement.
- Map the conversion stages. List every conversion from utility to chip, with its location, heat output and efficiency at the loads you expect. Compare options by stage count and by loss at partial load, not just peak efficiency.
- Define fault domains. Decide what a fault takes down at the rack, row, hall and power room levels, and which device clears it at each level.
- Set redundancy from workload behavior. See the next section.
- Specify protection and monitoring. Include breaker and fault-clearing devices, grounding scheme, isolation, telemetry and alarms. Requirements for this must come from your jurisdiction and the equipment vendors.
- Couple power and cooling. Budget heat from power conversion equipment, and check that liquid cooling and power layouts do not compete for the same routes.
- Plan commissioning and operations. Write procedures for energizing, isolation, lockout and maintenance before equipment is installed.
What redundancy do AI racks need?
The answer follows from what a failure does to the workload. NVIDIA’s DGX H100 SuperPOD documentation gives a concrete example. Where one system failing stops a multi-node job and recovery from a checkpoint is unavailable, each system rack needs at least three power sources fed from discrete upstream paths. NVIDIA rejects basic 2N for those racks because the loss of one power source can drop power supplies below the level the system requires. Its enhanced N+1 configuration uses three discrete UPS systems and distribution paths. NVIDIA describes it as optimal for maximum performance and reliability of DGX H100 system racks. The same documentation notes that many data centers are not built with three discrete UPS paths.
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Documentation and verification
NVIDIA’s guide recommends that qualified facilities or electrical personnel verify the supplied kVA against specifications and keep clear source labels. For any design, document:
- Source-to-rack paths and the breaker or circuit identity on each.
- Phase balance, where AC distribution is used.
- Capacity at each PDU and circuit, against the connected load.
- Redundancy validation by test, including what happens when each path is removed in turn.
- Connection labeling at both ends of every feed.
How to power a megawatt rack safely
OCP describes an evolving safety approach built from proven connectors, protection devices, breakers, fault-clearing solid-state breakers and advanced monitoring. Its DC backbone options include BESS integration and DC UPS functionality. These are design directions and requirements work in progress. Several decisions remain yours to make for the project and the jurisdiction:
- Protective-device coordination: DC faults do not have an AC zero crossing, so the interrupting device and its coordination across power room, hall, row and rack need engineering, not assumption.
- Grounding scheme: choose and document it. The ±400 V and 0–800 V options OCP names differ in how the conductors are referenced.
- Isolation and arc-flash: run the analysis for the actual equipment and set work practices to match.
- Commissioning and operating procedures: include energizing sequence, lockout, and who is qualified to work on live DC.
Monitoring is part of protection. Telemetry on power, temperature and breaker state at each boundary lets operators see a developing fault, and OCP’s AI infrastructure contributions list energy storage, telemetry, facility power distribution and rack and cluster architecture together.
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Keep cooling and power in the same design
At these densities the two cannot be designed in sequence. The conversion equipment adds heat and occupies floor space that cooling distribution also needs. A power rack or sidecar uses row space that would otherwise hold compute. A DC-native block changes where heat is rejected. Settle the row and hall layout with both disciplines present, and check capacity margins on both sides at the same growth case.
Roadmap, ecosystem and availability
NVIDIA reported in 2026 that its MGX-compatible 800 VDC power rack was expected in the second half of 2026 and the row power center, supporting up to 2 MW per row, in 2027. These are announced targets. Since the first of those windows is the current one, confirm the actual product status, certification and delivery to your region before basing a schedule on it.
NVIDIA and OCP describe an ecosystem covering power racks, busways, connectors, DC-DC converters, transformer rectifiers, solid-state transformers, and protection and monitoring. NVIDIA names partners including ABB, Analog Devices, Delta, Eaton, Flex, GE Vernova, Hitachi Energy, Infineon, LiteOn, Schneider Electric and Vertiv among others, and says more than 80 equipment manufacturers and infrastructure companies are building to the 800 VDC specification. OCP says more than 80 partners are developing compatible infrastructure. Those are the companies’ own ecosystem counts. A partner listed in a roadmap does not mean the product is orderable, certified or supported in your market.
Questions only your project can answer
- Which electrical code and inspection regime apply at the site?
- What are the utility service voltage, capacity and interconnection limits?
- What are the rack load, transient profile and growth plan, and what does the compute platform require?
- What recovery and redundancy objectives apply to jobs and to facility operations?
- Which products are orderable and certified in your geography today?
If you can answer these, you can pick a path with a defensible rationale. If you cannot, the first deliverable is a requirements document, not a one-line diagram.
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