A method and apparatus measures electrical power usage and quality, while mitigating the effects of noise on measured signals or parameters. Specifically, a digital electrical power and energy meter employs a method in which a processor averages a parameter, such as voltage or current, over a plurality of cycles of a time-varying signal, such as an AC electrical signal. The method employed by the meter samples a parameter over the plurality of cycles and computes the average of the samples corresponding to the same phase angle of the signal to produce an average signal.