We often measure data centers and other critical facilities in terms of capacity. Capacity is used to measure power, cooling, and of course space. Saying a facility has 50,000 sq ft of computer room space doesn’t really describe its actual capacity. Instead the depiction needs to include how much load can be supported such as 50,000 sq ft at 100 Watts/sq ft (or equally 50,000 sq ft and 5 megawatts of critical load). Implied in this description is that there is sufficient HVAC (including redundant) capacity to cool the heat generated by the critical load.
The point is that the “rated” capacity of a critical facility assumes there is a match between the physical size, available power, and respective cooling parameters. Otherwise, the actual capacity of the site is limited by the most restrictive parameter (space, power, or cooling). This balancing act is an inherent challenge that each architectural and engineering (A&E) firm meets when they design and engineer a new facility or modify an existing facility.