ASHRAE Standard 90.4 establishes the minimum energy efficiency requirements of data centers for design, construction, and operation and maintenance, and utilization of on-site or off-site renewable energy resources.

The standard was developed to be code-intended, similar to Standard 90.1, and references in Standard 90.4 are made to Standard 90.1 for building envelope, service water heating, lighting, and other equipment criteria. In addition, Standard 90.4 references Standard 90.1 for mechanical cooling equipment efficiencies. Standard 90.4 is a performance-based design standard that offers the design components of mechanical load component (MLC) and electrical loss component (ELC).

Calculations of MLC and ELC are made and then compared to the maximum allowable values shown in the standard based on climate zones. Compliance with Standard 90.4 is achieved when the calculated values do not exceed the values contained in the standard. An alternative compliance path is provided that allows tradeoffs between MLC and ELC.