Data-center power voltage: from 48V to 400/800V
As rack power rises, data-center power architectures are being discussed in terms of higher voltage. Because current equals power divided by voltage, delivering the same power at a lower voltage increases current and expands conductor cross-section, copper loss, and heat. As AI racks exceed 100kW and move toward 1MW, the question is how to choose among 48V, +/-400V, and 800V.
48V DC: the conventional in-rack standard
In-rack 48V DC has been the standard power architecture. Power supply units(PSUs) create a 48V bus, and DC-DC converters on the server board supply around 1V to each device. Its strengths are field experience and mature components. At higher rack power, however, staying at 48V makes current enormous, exposing limits in conductors, copper loss, and space. That is the starting point for moving to higher voltage.
+/-400V / 800V DC: the shift to HVDC
Hyperscalers are driving the move to raise the voltage entering the rack to high-voltage DC(HVDC). In the disaggregated(sidecar) power-rack concept described by OCP(Open Compute Project), power delivery shifts from in-rack 48V DC to +/-400V or 800V DC, enabling 100kW-to-1MW IT racks. +/-400V has relatively lower insulation and protection hurdles than 800V, while 800V lowers current further and is easier to scale toward the 1MW class.
NVIDIA's technical blog says an 800V DC architecture can improve end-to-end efficiency by up to 5% and reduce maintenance cost by up to 70% (NVIDIA Technical Blog). NVIDIA also says it will lead the transition to 800V for the 1MW rack generation from 2027 onward.
48V DC(in-rack standard)
Proven and built on mature components. Because low voltage means high current, conductors, copper loss, and space become constraints as rack power rises.
+/-400V DC
Reduces current versus 48V, while insulation and protection hurdles are relatively lower than 800V. It is an intermediate transition path.
800V DC
Lowers current further and fits the 1MW class more easily. It has efficiency and maintenance advantages(NVIDIA), but insulation and DC interruption design become harder.
Selection axes
Choose based on rack power range, tolerance for insulation/protection complexity, lead times for compatible components, and standardization trends(OCP).
How to choose: where the transition stands
The voltage choice depends on the rack power range, design tolerance for insulation and DC protection, and procurement lead times for 800V-compatible components. The current state is that 48V remains the proven standard, while the transition toward +/-400/800V is beginning. Facilities, power supplies, and devices are updating their designs in the same direction. Related articles cover the overall architecture and transition schedule in more detail.