This Guide is developed by FEMP in collaboration with the Lawrence Berkeley National Laboratory. The Guide is an introduction to a temporary wireless mesh assessment kit, a data center monitoring system which can be used to reduce equipment costs and shorten the time frame of a traditional data center energy use assessment. The assessment kit helps to create an accurate evaluation of data center operation, air management, and Power Usage Effectiveness (PUE) at lower cost and with greater efficiency. The guide also details the advantages of the wireless assessment kit versus traditional data center monitoring, the process for installing and operating the assessment kit, and basic information and background on data center monitoring and evaluation. The guide is intended for personnel responsible for managing data center energy use, including IT and facilities managers.