An energy meter measures the amount of electrical energy consumed. Electrical energy consumed is essentially a product of power and time, or in other words, power is a simple product of instantaneous voltage and current. There are several key requirements for a good eMeter: the first is that it has to have good ADCs because it has to accurately sample voltage and current, instantaneously so there are not any phase shifts in the software; and second is that it has to have enough processing power to do all the powerful math. Another important feature of an eMeter is accuracy of computation, which is important because billing is involved. The consumer does not want to pay more, and the utility company does not want to get paid less. So industry standards today require 0.1% accuracy in the measurements, and that requires a high resolution ADC, typically the more bits the better the conversion from analog to digital. Also, the eMeter processor needs to support functions like square root, square division, etc. and that means it has to support good libraries.