Megawatts to Kilowatts

Stepping a Data Hall's Megawatts Down to the Cabinet

A colocation contract, a build programme and a utility reservation are all written in megawatts of IT load. Nothing inside the white space works at that scale: the busway tap, the rack PDU, the branch breaker and the cabinet label are in kilowatts. A facility engineer spends a surprising amount of the working week moving between those two views of the same building.

Conversion factor: 1 MW = 1,000 kW, so multiply megawatts by 1,000. A 2.5 MW data hall is 2500 kW of IT load, which at 12 kW a cabinet fills about 208 racks — and at 40 kW a cabinet, only 62.

The Layers the Number Passes Through

Campus and hall capacity

The headline figure a site is marketed and permitted with, split into halls or data suites that each get their own megawatt allocation.

The redundancy block

UPS modules, generators and distribution boards are bought in blocks, and the usable kilowatts depend on whether the topology is N, N+1 or 2N.

Cabinet allocation

Each cabinet gets a contracted kilowatt figure, and the sum of those allocations — not what the servers actually draw — is what fills the hall on paper.

Accelerated compute

A single training rack can consume what an entire legacy row once did, so a hall designed on old averages runs out of kilowatts long before it runs out of floor tiles.

From Hall Allocation to Cabinet Schedule

The order that avoids arguments later: start from the contracted IT load, spend it in kilowatts, and keep the facility-side figure in a separate column.

Enter the hall's IT load in megawatts

Type 1.5, 2.5, 12 — whatever the allocation is — in the left field and read the kilowatt budget you have to spend. A comma works as a decimal separator, so 2,5 and 2.5 both land on 2500 kW.

Divide by the density you are designing to

Split the kilowatt budget by the per-cabinet figure to get the rack count the hall can actually carry. The answer moves faster than people expect: the same 2500 kW is 312 cabinets at 8 kW but 31 at 80 kW.

Reverse once the cabinet list exists

When the schedule is built bottom-up, add the per-cabinet kilowatts and press the swap button (↔) for kW → MW to see whether the total still fits the reserved capacity. 40 cabinets at 30 kW is 1200 kW, or 1.2 MW of the block.

Move the figure into the power schedule

The copy button gives the bare number without unit or spacing, which drops cleanly into a DCIM field or a capacity spreadsheet. Ctrl + C inside a field copies the same thing.

IT load and facility load are two different budgets: the megawatts in a colocation contract are what the servers may draw. Cooling, UPS losses, lighting and controls sit on top, and a PUE of 1.3 means a 2.5 MW hall pulls about 3.25 MW at the meter.

Rack Density Classes and Cabinets per Megawatt

Per-cabinet densities from legacy enterprise rooms up to accelerated compute, with the cabinet count each supports on one megawatt and on a two-megawatt block.

Density class	Per cabinet	Cabinets per 1 MW	Cabinets per 2 MW
Legacy enterprise room	3 kW	333	667
Mixed enterprise floor	5 kW	200	400
Standard colocation cabinet	8 kW	125	250
Recent build average	12 kW	83	167
High-density, air cooled	20 kW	50	100
Rear-door or liquid assisted	40 kW	25	50
Accelerated compute	80 kW	12.5	25
Direct-to-chip AI rack	120 kW	8.3	17

One megawatt used to be a room full of cabinets; at the top of this table it is eight of them. That collapse in footprint is why megawatts, not square metres, became the unit a data centre is sold and valued in — and why a hall built around a 5 kW average cannot simply be refilled with modern racks without redoing the distribution.

Useful While the Capacity Plan Is Open

Hall megawatts and cabinet kilowatts side by side

Both fields update together, so you can try 1.5, 2 and 3 MW allocations against the same density without losing your place.

Bottom-up check on a finished rack list

Swapping to kW → MW turns a summed cabinet schedule back into the block figure the capacity report is written in.

Watts and gigawatts for the campus roll-up

The searchable dropdowns hold every power unit, so a single server's watt figure and a multi-site gigawatt programme use the same two boxes.

Clean values for the power schedule

Thousands are shown with a space for readability, while copy hands over the raw digits your DCIM field will accept.

White Space and Power Budget Questions

Is a 10 MW data centre 10 MW of IT load or 10 MW from the grid?

Almost always IT load — the 10 000 kW that reaches servers, storage and network gear. The grid figure is larger, because everything supporting that equipment is outside the number. When a site is described as 10 MW it is worth asking which side of the UPS the meter sits on before comparing it with another operator's claim.

How does PUE change the kilowatts I have to supply?

PUE is total facility power divided by IT power, so multiply. At 1.5 a 2 MW hall needs 3000 kW at the boundary; at 1.2 the same hall needs 2400 kW. Most well-run modern sites sit between 1.2 and 1.4, older mixed-use rooms considerably higher, and the very best hyperscale fleets report figures near 1.1.

How many cabinets fit in a 1 MW data hall?

Power decides it long before floor area does. 1000 kW is 125 cabinets at 8 kW, 83 at the 12 kW that recent builds average, and 50 at 20 kW. In practice halls are laid out at a design density and then filled unevenly, so a good plan leaves spare kilowatts in each row rather than assuming every cabinet lands on the average.

What stops cabinets going past 100 kW?

Two limits arrive together. Air stops carrying the heat away somewhere around 20–30 kW a cabinet, so anything higher needs rear-door heat exchangers or direct-to-chip liquid. And the electrical side gets awkward: 120 kW down a conventional three-phase feed means very large conductors, which is why 800 V DC distribution is being designed into the newest AI halls.

How does N+1 redundancy affect the kilowatts available on a block?

The usable figure is the block without its spare module. Five 500 kW UPS units in N+1 total 2500 kW of hardware but only 2000 kW, or 2 MW, of load you may actually place. A 2N design goes further and holds two complete paths, so a hall fed by two 2 MW systems is still a 2 MW hall — sizing from the nameplate sum is the classic way to overfill a block.