What is a busway in data center and why hyperscalers no longer use traditional cabling

Why hyperscalers stopped running copper between the transformer and the rack

Traditional electrical distribution in a data center uses copper cable in trays above the ceiling or below the raised floor: thick runs from the transformer to the distribution panels, then thinner cable to each rack. That model was designed for a reality where each rack drew between 5 and 15 kW. When the average rack rose to 30, 60 or 100 kW to feed the new AI loads, copper cable stopped being viable both physically and economically.

The physical problem with copper at high density

To see the problem, the basic numbers:

• A 4 AWG cable (common for 30A rack feeders) weighs about 0.25 kg per meter.
• A 500 MCM cable (required for 400A feeders) weighs about 3.3 kg per meter.
• A rack drawing 100 kW at 415V three-phase needs about 140A per phase. That requires 1/0 AWG or larger cable, weighing 0.6 to 1.0 kg per meter.

Scale this to a row of 20 racks at 100 kW each. If each rack needs its own 1/0 AWG feeder, that is 20 cables running in parallel along the upper tray. The combined weight exceeds the structural capacity of most existing cable trays. The physical space in the ceiling plenum or below the raised floor does not fit. A North American colocation operator that tried retrofitting three halls for AI tenants in 2025 found that their existing cable infrastructure, designed for 8-12 kW per rack, had no residual capacity for the 80-100 kW per rack the new tenants required. Adding parallel cable runs was estimated at 14 weeks per hall and almost $3 million per facility, and the available plenum space under the raised floor could not accommodate the required volume at any cost.

What a busway is

A busway is a system of factory-prefabricated conductor bars that are assembled on site, suspended above the data center plenum or integrated into the structural ceiling. The bars can be copper or aluminum, encapsulated in a metallic or solid-insulation housing. Typical nominal current ranges from 400A to 2,500A per bar, at voltages of 415V to 800V AC or DC.

Unlike traditional cable:

• The sections arrive pre-engineered from the factory, with defined connection points and tap-offs.
• They mount to the ceiling or to an elevated structure, completely freeing the floor plenum.
• They have tap-off points at regular intervals (typically every 600-1,200 mm), where junction boxes feed each rack or row of racks.
• The tap-off boxes are hot-swappable, meaning they can be added, moved or relocated without cutting power to the rest of the busway.

That last characteristic is what changes the economics of electrical distribution in a data center.

The adoption numbers behind the shift

The global data center busbar trunking market is projected at $2.1 billion in 2026, with an expected $4.5 billion by 2032, a 13.5% CAGR per MarketsandMarkets. More than 65% of new facilities above 10 MW are adopting busway instead of traditional cable tray, according to Business Research Insights analysis.

Adoption by operator type:

• More than 75% of colocation providers above 5 MW have integrated modular busway to support densities above 15 kW per rack.
• Hyperscale operators adopted it from 2018-2020; it is now standard in new campuses.
• Edge data centers equipped with busway grew 38% globally in 2023, with more than 5,700 facilities incorporating compact designs.

Aluminum has gained ground: aluminum bars are 30% lighter than copper and offer 15% material-cost savings. At sites with sensitive CAPEX budgets, the difference is material.

The technical reasons hyperscalers switched

Three concrete technical reasons drove the change:

1. Reduced voltage drop. A well-designed busway has voltage drop below 1% over 30 meters, compared with 2-3% for equivalent cable runs. For a feeder powering 7 MW at 415V three-phase along a row of 20+ racks, that translates into directly measurable energy efficiency at the rack level.

2. Reconfiguration speed. Reconfiguring electrical distribution with cable takes an average of 9 hours per change, with a power cut included. With modular busway and plug-and-play tap-offs, the same change takes less than 3 hours, per Business Research Insights analysis. In AI operations where loads change weekly, that difference defines operational viability.

3. Copper reduction. Busway uses approximately 20% less copper per MW deployed compared with traditional cable systems. At the scale of a 100 MW campus, that is tens of tons of copper avoided.

Vertiv launched in March 2026 its PowerBar Track double-stack system, supporting up to 2,000A under UL 857 and 2,500A under IEC 61439-6, specifically to address AI loads in colocation and hyperscale. Square D (Schneider Electric), Starline (Universal Electric), Siemens and Eaton have comparable products in the market.

The 800 VDC case that is coming

The next evolution is already underway: 800 VDC distribution instead of 415/480 VAC. NVIDIA presented in 2026 its roadmap to 800 VDC with Kyber systems in 2027, citing up to 5% end-to-end efficiency improvement versus the traditional 54V path, 85% more power per conductor at 415 VAC, and 45% less copper.

800 VDC is not a new way of generating electricity; it is a distribution architecture that converts medium-voltage AC once at the hall perimeter, runs 800V DC along busway instead of 415/480 VAC feeders, and converts once more at the tray to the voltage the GPU draws (54V, 12V or 6V).

For Mexican data centers, 800 VDC is still at an early adoption stage. But the architectural decision between traditional cable and AC busway must be made now in any new project above 1 MW, because retrofitting later is exactly the scenario no operator wants to face.

What your next electrical RFP should ask

To properly specify the electrical distribution of a new data center, the questions that must appear in the RFP:

• Does the distribution system use modular busway or traditional cable in tray? What is the CAPEX delta between the two options?
• What is the target per-rack density today and at 5 years? Will the system support that density without infrastructure replacement?
• What is the nominal amperage of the busway and at what distance can tap-offs be placed?
• Are the tap-offs hot-swappable without power cut?
• What is the estimated system reconfiguration time (in hours)?
• What is the expected voltage drop over the longest run?
• Does the provider have experience with projects at the specific scale being designed?

The answers to those questions indicate whether the electrical system of the new data center is designed to support the operating density of the next 10 years, or whether it will be obsolete in 3.

Sources

1. MarketsandMarkets (2026). Data Center Busbar Trunking Market Report 2026-2032. https://marketsandmarkets.com/Market-Reports/data-center-busbar-trunking-market-109828729.html
2. Business Research Insights (2025). Data Center Busway Market — Industry Analysis Report 2035. https://businessresearchinsights.com/market-reports/data-center-busway-market-107956
3. Compute Forecast (2025). Copper to Busbars: How Modern Data Centers Are Redesigning Internal Power Distribution. https://computeforecast.com/long-reads/copper-to-busbars-data-center-power-distribution
4. Rax.ae (2026). Megawatt-Scale Rack Power Delivery: 100 kW to 1 MW Per Rack for AI & HPC Data Centers. https://rax.ae/knowledge-center/articles/megawatt-rack-power-delivery-high-density-data-centers.html
5. Inside Deep Tech (2026). 800 VDC Power Distribution: A Full Guide to How AI Data Centers Leave 48-Volt Behind. https://www.insidedeeptech.com/800-vdc-power-distribution-ai-data-centers-full-guide/