My Kill A Watt P4400 by P3 International shows 3 watts electricity usage if anything is plugged in. Do things plugged in, regardless of whether they are ON or OFF, really use a minimum of 3 watts or is it an inaccuracy on the part of the Kill A Watt?

Pardon me if I misuse terminology; I'm not too familiar with electrical terminology, only electronics.

  • 2
    Sounds like an inaccuracy in your meter. Mine reads zero watts with nothing plugged in (or something plugged in but powered off with a hard power switch). Some devices (like TV's, DVD players, etc, anything with a "soft" power switch or remote control) will use some power even while they appear to be turned off.
    – Johnny
    Commented Jan 4, 2014 at 21:28

2 Answers 2


To test, plug a non-electronic lamp in, and turn the lamp off. Your P3 should show zero watts, or it is clearly defective.

Many electronic devices have "parasitic" or "phantom" or "vampire" power usage: I have a toothbrush charger that shows about four watts, 24 hours a day, 7 days a week. There's a radio that when off shows about ten watts. And several Apple chargers that show a big zero when charging is done, due to better technology.

Note with the P3 you'll have to measure over a period of a few days, to accurately measure devices that draw less than one watt.

Here's an example study on the topic: http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1046&context=eesp See also: How do you determine how much electricity is used by a device?


It certainly is an inaccuracy. In Europe, since 2013, home appliances may draw at most 0.5 Watt in their stand-by mode, and many draw less. And it’s not just stand-by – if for example a phone charger rated at 1W output would draw over 1.5W, I’d return it as defective.

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