I would like to replace a couple of electrical outlets in my house with ones that have USB sockets. My concern is that they will continually draw power, even when I don't have a phone plugged in to them

  • Like Adam said.. they will draw a small current until something is plugged in. To avoid that you have to find plugs then when you switch it off.. it shuts down the usb power too- or diy it and move the usb power line after the switch if it not like that already.. green peace dude..
    – Piotr Kula
    Commented Jul 23, 2012 at 16:04

4 Answers 4


It is very unlikely that they won't. Nearly all AC to DC converters, by design, draw a very small idle current when you aren't charging any devices. Cheaper designs consume more while some good designs consume less, but unless there's a physical switch on the USB socket it will always consume some power while waiting for a device to be plugged in.

These are new sockets to the market, and unless you have a compelling reason to avoid a plug in USB charger I would recommend holding off anyway. Not only do you have the continuous current draw (which, honestly, is going to be less then $5.00 per year even if the device is terribly inefficient) but there's the likelihood of the socket failing, and it's not nearly as easily or cheaply replaced as a plug in charger. Further it may not charge all devices at their full current. While the USB association has suggested designs for high power charging (above 500mA), many manufacturers (notably, Apple) still use their own scheme for detecting 1A and 2A charging currents.

Most phones and PDAs will only charge at 1A or greater when connected to their own charger, and at the slower 500mA rate when they can't detect their own charger.

There are probably some applications and situations where it might be useful, for those prone to losing their chargers, for instance, but there are many reasons to reconsider using them.

  • 4
    Modern usb chargers pull about 0.05 watts from the wall with nothing plugged in. That's closer to 5 cents a year rather than $5/yr.
    – marathon
    Commented Jul 28, 2017 at 17:52

This product has little spring-loaded doors on the USB ports that completely shut off the power supply when they're closed.

  • Nice find! The only downside to this product is that it recommends that if you want to charge your iPad at the full apple charging rate, you should still use a plug in charger. Sounds like it'll work well for cell phones and regular charging rate devices.
    – Adam Davis
    Commented Jul 27, 2012 at 14:23

You will most likely have to find the results of a test of the specific model you are considering purchasing. It depends entirely on the design of the power supply built into the outlet, and there is a lot of room for variation.

You could conduct the test yourself by buying one such outlet, wiring it temporarily to a plug, and using a plug-in power meter or clamp meter to measure the current/power draw. Make sure the meter has enough resolution to report this very small load.


Vampire power on modern devices is negligible. This site did a test, they couldn't get a reading with their equipment with any single charger. They had to plug a bunch in. 6 devices plus the led light on the power strip was 30 cents/yr.

The combined total vampire power draw of this power bar, an iPhone 6 charger, an iPad Air charger, a MacBook Air (2013) charger, a Surface Pro 2 charger, a Samsung Chromebook charger, and a Nexus 7 charger read 0.3 watts.


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