Practical issues in monitoring and reporting input and output power

Concerns about the consumption of energy by information technology (IT) equipment are driving a concerted effort to manage and reduce this power consumption. One of the most important metrics for energy management systems is the current power consumption. IT equipment power supplies are now generally required to report their input power with accuracy in the range of 2-5%. This paper describes some of the computational issues in monitoring and reporting equipment input power. It also describes a method for a power supply to report its input or output power without requiring the power supply to compute averages or have a real time clock.