In-wall USB charging is here--well, almost--with the Truepower U-Socket, which is currently awaiting UL Approval and should be available within months. The $19.95 socket can be self-installed if you've got a little know-how; an installation video will be "available shortly" so you can decide if you're up to it or not.
One thing I don't understand is that the product description says
...The USB ports only draw power when something is physically connected to the port. We didn't want a vampire port that continually sucks and wastes power when not in use so this was one of the features on the top of our priority list during the design phase.
Isn't that true of regular plugs as well, that they only draw power if something is connected to it? I have a hard time believing that even my plugless outlets are leaking power. Please let me know in the comments if I'm misinformed.
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These are available in various guises for Uk and US styles of mains, as well as including USB. Hunting will also reveal USB only sockets - sans mains sockets.
I'm not saying where though, as u am going to be reselling them online soon! C'mon get some!
Basically in your standard outlet when nothing is plugged in you have an "open circuit". There is no current flowing and hence no power (for simplicity sake, assume power equation is P=V*I ).
Now... what they are doing here is aside from providing you with your standard AC they are providing 5Volts DC for the USB. This is usually what your "power brick" or "wall-wart" is doing. So basically stepping down the voltage and rectifying it... since USB devices draw significantly small amount of current they are able to accomplish this by using solid state devices, 'chips' or little microcontrollers. We have recently shrunk this technology considerably, remember the old iPhone charger compared to the tiny new one? (your macbook charger is still big because of the larger current requirements). So you have to power this chip and even with no load attached to it, could potentially be using small amounts of current depending on the specific chip to stay in some form of stand-by or active state.
I would take this discussion in the direction of the new "smart-home" devices coming out. In order to monitor all the electricity in your home, technically point out where you can save and such... but we have to keep in mind that in order to monitor this we have to waste power... kind of a catch22. Of course one can argue that this might be a negligible power consumption but I would like to see the numbers, especially when we are talking about a good couple dozen of outlets in a home, couple hundred on your street and hundreds of thousands in your city... is the "smart-home" so smart?
Sorry for the long post and tangent but then again... I am an Electrical Engineer...
On the other hand, how useful is technical information from people who can't read??
Honestly people.....
Very cheap power adapters, generally big wall-warts, will use electricity even if nothing else is plugged into them, quietly turning electricity into waste heat. Higher quality/more expensive adapters behave as quoted, only drawing power when there's a reason to, which is great for in-socket devices since they're always plugged in.
The electricity supplied to your home (which is what comes out of a standard power socket) is ~120 VAC, but a USB port needs to deliver 5 VDC, so there must be a transformer and some sort of rectifier to step down the voltage and convert AC to DC. These circuits are traditionally lossy (like how a plugged in wall-wort DC adapter will be slightly warm even with no device attached to the other end).
In this case the manufacturer is claiming their designs doesn't waste power on the electronics behind the USB port -- they probably only power on when something is socketed.
However, you need to think of this unit as 2 separate electrical units (now joined): 110V plugs and 5V USB ports. To work the USB ports, 110V need be be stepped down via a transformer to 5V .... that process would normally draw power (even without a device been plugged in). I'm presuming that the designers placed a "switch" into the unit that turns off the transformer until such time as a USB device is plugged in. The picture of the unit appears to show an indicator light/port (upper right) that presumably comes on once the USB port is in use.
However the circuitry in this device that converts the 110 volts to 5 volts is the same type of circuitry found in the typical wall wart charger. Most of those chargers will continue to draw power whether a device is charging or not. It's great that they designed this so it didn't have that problem. ...
Personally though, I would have liked to see this designed to fit into the standard Decora wall plate format. If they'd only provided a single AC socket, they could have easily fit two USB outlets above or below.
Most of the time DC power is supplied to our devices via wall warts that continuously draw power so long as they're plugged in. Somehow they are switching the power supply off completely when nothing is connected to the USB ports so that is doesn't continuously draw power.
Normally, transformers plugged into the mains DO suck constant power, but it seems this one has some circuitry to prevent that. That's my take on it anyway.
The USB connection needs an adapter to bring the power down to 5V just like an external power brick would do. This is what continually wastes power even if not connected to a device. The power wasted is from conversion inefficiency (~70-80%) which is converted to heat.
With the regular wall socket, there is no conversion needed, as you would connect straight to 120VAC wiring.
A constantly on USB port would be kinda like having a phone/laptop charger plugged in to the wall, yet not into your laptop. It's constantly on and using energy regardless of being plugged into your device.