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Data center power explained: kW per rack, N+1, 2N and PUE
Power decides what a data center can host and what it costs to run. These are the terms to know.
Updated: 2026-11-09
Capacity and density
Power is sold in kilowatts (kW). Density is kW per rack. Traditional enterprise racks draw a few kW; AI and high-performance computing racks can draw far more and often need liquid cooling. Check both the per-rack limit and the total capacity available to you.
Redundancy: N, N+1, 2N
N is the capacity you need with no spare. N+1 adds one spare unit, so one can fail. 2N duplicates the whole system. More redundancy raises resilience and cost.
PUE
Power Usage Effectiveness is total facility energy divided by the energy used by IT equipment. A value closer to 1.0 means less energy goes to cooling and overhead. Ask how the provider measures it and over what period.
What is a good PUE?
Lower is better and 1.0 is the theoretical floor. Climate, design and load change what is realistic, so compare sites measured the same way.