Thoughts on those plug-in power savers vs. traditional efficiency upgrades?

I opened one of those "Eco-Watt" style boxes a few years ago after my neighbor bought a bulk pack. Inside was literally just a small capacitor, a fuse, and an LED to make it look like it was doing somthing. The theory they use to sell these is power factor correction, wich makes sense for a huge factory full of massive motors, but it’s a total wash for a house. Most residential utility companies bill you for "active power" (kilowatt-hours), not "apparent power" (kVA). Even if that capacitor slightly shifts the phase of your current, your meter isn't going to tick any slower. I actualy hooked one up to my Kill A Watt meter out of curiosity. The draw was negligible, but it certainly didn't reduce the consumption of my fridge or AC unit.

Your dad whould be much better off spending that money on a decent smart thermostat or even just swapping out any remaining halogen floods for LEDs. Those boxes are basially just nightlights that consume a tiny bit of extra juice themselves. It's frustrating to see companies prey on people trying to shave a few bucks off thier monthly overhead.

I think we’re being a bit too quick to dismiss the basic physics here. While those cheap $10 plug-in units are definitely bottom-barrel, I installed a more robust KVAR unit at my workshop where I run a lot of older inductive loads like my lathe and a heavy-duty compressor. My utility bill didn’t drop by 30% like the ads claim, but I did notice a measurable difference in heat coming off my main breaker panel during heavy usage. Before the install, I used a Fluke thermal imager and saw some significant hot spots on the lines feeding my heaviest motors. After adding the correction unit, those temperatures dropped slightly. For someone like your dad who might have an older AC unit or a pool pump constantly cycling, reducing that reactive current can actually help with the life of the appliance motors. It’s less about the monthly bill and more about protecting the hardware from internal heat stress and filtering out some of the line noise that messes with sensitive electronics. If he’s allready bought them, it’s probably not hurting anything as long as the internal fuses are rated correctly. I’d rather see a proper whole-house surge protector at the panel, but calling it pure junk ignores the benefit of localized capacitance in homes with high-inductance equipment.

Total snake oil for a standard residential split-phase system. If you relly want to see what's happening at the panel, grab a Sense Home Energy Monitor or a Fluke 376 FC and actualy measure the draw. Those generic 'Power Save' boxes are ussually just a 5uF capacitor in a cheap shroud. I’ve seen some of these knockoffs get hot enought to melt the casing becasue they're built with zero UL oversight. Tell your dad to put that money toward a Leviton Load Center or some high-efficiency AFCI breakers instead. At least those serve a purpose when a transient hit or a ground fault actually happens.

The marketing regarding 'voltage stabilization' is particularly egregious because these units almost universally lack the Metal Oxide Varistors or filtering circuitry required to actually suppress transient spikes or attenuate the harmonic distortion endemic to modern switch-mode power supplies. Even if one charitably interprets these as rudimentary shunt filters, the internal components are so vastly undersized that they provide no meaningful mitigation of the inductive kickback from a standard compressor cycle. Rather than 'stabilizing' anything, you're merely introducing an uncertified, high-impedance component into your branch circuits that serves no functional purpose beyond illuminating an LED, whereas a legitimate Type 2 surge protective device at the panel would actually offer some quantifiable equipment protection.

Update: I actualy cracked one open like someone suggested and it realy was just a tiny capacitor and an LED. I’m thinking about getting a Sense monitor to show my dad the actual draw, but woud that even pick up the "correction" these boxes claim to do? Or shoud I just borrow a Fluke and measure the inductive loads directly like the shop owner mentioned?