In order to be eligible for ENERGY STAR certification, data center IT Energy readings should be taken at the output of the Uninterruptible Power Supply (UPS). See "A" in the diagram below.
The UPS output is a standard, uniform measurement location available to most Data Center owners. Many UPS systems already have energy consumption meters on them.
There are three exceptions to this rule:
1) If there is no UPS in the data center, then you can meter at the input to the Power Distribution Unit (PDU) (See "B" in the diagram above):
2) If the UPS supports non-IT loads that are more than 10% of its load (ex: the HVAC is also on this meter) and cannot be sub-metered, then you can meter at the PDU input. If the non-IT load can be sub-metered, then you should subtract it and enter the remainder as the UPS Output.
3) If your meter does not have an energy reading (kWh), but is able to record power (kW) every 15 minutes, then you can use a software solution that connects to the UPS to record power readings in kW every 15 minutes (or more frequently). Then calculate your monthly energy in kWh units.
If your property cannot utilize any of these approaches, see this FAQ for other benchmarking options.