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Why design capacity exceeds actual load
Electrical code treats anything running more than three hours as a continuous load, and a breaker may only be loaded to 80% of its rating continuously. So a 16 A circuit safely carries 12.8 A, not 16 A.
The calculator reports both figures. The IT load is what your equipment actually draws; the design capacity is what you need to order. Sizing to actual load rather than design capacity is the most common mistake in a first colocation order, and it means tripped breakers under load.
What 2N redundancy means for your order
A 2N configuration gives every device two independent feeds, A and B, from separate upstream paths. Dual-supply servers draw from both, so each feed normally carries about half the load.
The critical point is that each feed must be able to carry the entire load alone, because that is exactly what happens when the other fails. Sizing each feed to half the load defeats the purpose -- the survivor trips the moment it is needed. The per-feed figure here shows the normal split; provision each feed for the full amount.
Cooling follows power almost exactly
Essentially all the electrical energy a server consumes leaves as heat, so cooling load tracks power load closely. One watt of IT load produces 3.412 BTU per hour, and a ton of cooling removes 12,000 BTU per hour.
That conversion is why power and cooling are quoted together. What varies between facilities is how efficiently that heat is removed, expressed as PUE -- a facility at 1.5 PUE spends half a watt on cooling and overhead for every watt of IT load.
Density changes what you can buy
Rack density is often the binding constraint rather than total power. Many older colocation halls are designed around 3-5 kW per rack, and standard raised-floor airflow struggles much beyond that.
Above roughly 10 kW per rack you need hot or cold aisle containment, in-row cooling, or rear-door heat exchangers, and not every facility offers them. If the calculator shows high per-rack density, spreading the same equipment across more racks at lower density is often cheaper than paying for high-density infrastructure -- worth pricing both ways.
Frequently asked questions
Should I use nameplate wattage or actual draw?
Nameplate ratings are worst case and usually well above real consumption. Measure actual draw if you can; if you cannot, budgeting around 60-70% of nameplate is a common starting point, then confirm once deployed.
Why does three-phase give a different current?
Three-phase distributes load across three conductors, so for the same power the current per conductor is lower by a factor of the square root of three. That is why higher-density deployments use it.
Does this include cooling and overhead power?
No. It calculates IT load and the heat that must be removed. Total facility consumption also includes cooling and losses, captured by the facility's PUE.
Is anything I enter here sent to your server?
No. The calculation runs entirely in your browser and nothing is transmitted.