How can power be measured in datacentre?

Measuring power usage in a server room or datacentre can be important for a range of factors including capacity planning, energy efficiency, billing or business continuity. Active ‘Power present’ sensors can be used to determine if power is present and signal an alarm if there is a change in state i.e. a mains power failure. Metered and Intelligent power distribution units (PDUs) can monitor power levels and usage down to individual outlet sockets. Basic power measurement information can include Volts, Amps and energy (kWh) for each individual outlet and for the PDU as a total.