They do nothing to save you power Scam "power saving" devices are rampant online. These devices plug into an outlet and promise to "improve the use of energy," "extend the life of electrical equipment," and even "avoid illegal electrical waste." Sounds great, right? Also: This USB power meter I tested is shockingly accurate - especially for how cheap it is Well, despite the bold claims and the sticker on the front of the unit, they are too good to be true. Many of these units seem to be repurposed cases for rodent repellers, and coincidentally, many of those are also scam devices.