Why a power-factor correction device is better suited to industrial applications

How often are homeowners approached by a salesperson at the doorstep selling a device that can go in a wall and supposedly save energy or reduce the monthly electricity bill substantially? The so-called "power-saver device" (known by different names) is nothing but power-factor correction (PFC) device that connects to the mains and improves power factor, and thus the apparent power measured by the meter. However, it's important to notice that a residential user's utilities bill is based on real power rather than apparent power, and thus none of these devices really reduce their monthly bills. In this article, I explain the different power types that an electricity meter measures, power factor, and power factors' implications on power measurement. Although a PFC device may be useful for industrial applications, the additional cost does not really justify this device to be used in residential applications, contrary to the claims.