Do Receptacle Outlets With USB Charging Ports Use Power When No Load Is Connected?

Thread Starter


Joined Jan 15, 2013
Hi All!

I was wondering if the receptacle outlets, such as NEMA 5-15R in North America, that have built in USB charging ports use electricity when nothing is plugged into the USB sockets.

I've read that the plug-in-the-wall AC to DC rectifiers and AC Step Down adapters (both sometimes called "Wall Warts") do consume electricity when nothing is connencted to the load side. I've also read they don't use electricity with no load. Each article had a convincing argument. (Examples of what I'm not doing a very good job of describing as wall wart: Power supply for a laptop computer, Stand Alone USB phone charger)

My guess is yes both the USB receptacle and the wall wart will use power to keep the transformer saturated.
Did I get it correct, or do these USB receptacles not use power when nothing is plugged into the USB?

Thanks For Helping,



Joined Jun 5, 2013
The receptacles need the same circuit as a wall wart wart phone charger. They all use some power. It should be less than 1 Watt, but not all are.


Joined Aug 7, 2020
Of course, it wouldn't be beyond the wit of man to incorporate a microswitch to turn off the power when there was no plug in the socket, but that would make it more expensive to build, and so everyone would buy the cheaper one that adds 8.7kWh per plug to their electricity bill every year.