Is the Power Pro Genius worth buying, or just an expensive nightlight?

How the Power Pro Genius, and every power factor gadget, actually works

Open one of these up, and you generally find a small capacitor sitting across the live and neutral lines, sometimes paired with an LED and a thermal fuse. The idea, borrowed from real industrial gear, is power factor correction: a capacitor can offset the phase lag that inductive loads like motors and compressors put on the current, making the apparent power drawn look more efficient. That's real physics, and it works, on a factory floor where the utility partly bills large customers on power factor and a poor one costs real money. The catch is what happens when you scale that down to a small box in a household outlet. Residential meters, the ones actually reading your usage, bill you on real power, the watts your appliances turn into heat, light and motion, not on apparent power or phase relationships. A capacitor sitting near your router or lamp corrects a fraction of a fraction of your home's inductive load, and even a large correction wouldn't move a number your utility never calculates in the first place. This is the same physics behind so called dirty electricity filters and smart energy savers sold under a dozen names: real principle, wrong scale for a home meter. What you actually get for your outlet is a compact, overheat resistant box that draws a trace of its own power, sits there quietly, and lights up to say it's plugged in.