Critical Load
Critical load is the amount of power, measured in megawatts, that a data center can actually deliver to customer IT equipment on protected, redundant circuits. Critical load, not square footage, is the real unit of capacity in the data center industry.
Critical load describes the portion of a facility's electrical capacity that is backed by uninterruptible power supplies and generators and dedicated to IT equipment. It excludes power consumed by cooling, lighting, and building systems. When a provider announces a new facility as a fifty megawatt campus, the meaningful question is how much of that is critical load available to customers.
Density
Critical load per cabinet, usually expressed in kilowatts, determines what workloads a facility can actually host. Traditional enterprise racks might draw five to ten kilowatts. AI training and high performance computing deployments routinely require far more, which is why liquid cooling and high density design have moved from specialist concerns to mainstream requirements.
Contracted versus available
Buyers should distinguish between total built capacity, contracted capacity, and capacity actually available for sale today. In supply constrained markets these three numbers can differ dramatically.
Why it matters for marketing
Square footage is the vanity metric of the data center industry. Power is the constraint that governs whether a customer can deploy at all, and in most major markets power availability, not space, is what determines who wins a deal.
Facility pages that lead with total square feet and bury power density are answering a question nobody asked. Lead with available critical load, density per cabinet, redundancy configuration, and expansion runway. That specificity is also precisely what an AI assistant needs in order to surface a facility in response to a query about capacity in a given market.
Common questions
What is the difference between critical load and total facility power?
Total facility power is everything the building draws from the utility, including cooling, lighting, and building systems. Critical load is only the protected, redundant power delivered to customer IT equipment. Because cooling and overhead consume a meaningful share, critical load is always lower than total facility power. The ratio between the two is essentially what PUE measures.
Why is power density more important than square footage in colocation?
Because most modern deployments run out of power long before they run out of floor space. A high density AI or HPC workload may fill a cabinet's power budget at a fraction of the footprint a traditional enterprise deployment would occupy. Buyers evaluate kilowatts per cabinet and available megawatts, not square feet.