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Does a (phone|laptop) charger plugged in the socket but not connected to the device still consume electricity? (lemmy.ml)

submitted 11 months ago* (last edited 11 months ago) by [email protected] to c/askscience

18 comments fedilink hide all child comments

And if so, how much? Less, same or more than if it was actually charging something?

I'm in the EU if that changes something.

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[–] [email protected] 51 points 11 months ago* (last edited 11 months ago) (4 children)

Depends on the charger but either effectively zero or considerably less.

People get pissy about it, but think of electricity like water. Having a longer pipe is a negligible amount of water if the faucet is still off. And the faucet can only turn on if your device completes the circuit by being plugged in (and doing the appropriate handshakes)

That said, some chargers will consume a negligible amount of electricity to actively listen for a device. Think of it like the water in your toilet. Every so often enough evaporates or leaks that you hear it run a bit to refill. But mostly it is nothing until you flush.

[–] TallonMetroid 11 points 11 months ago

Here's an article on it, in case you wanted to know how to go about verifying it for yourself.

[–] clockwork_octopus 6 points 11 months ago

As an electrician I approve this analogy

[–] [email protected] 4 points 11 months ago (1 children)

I use a short lightning cable to plug my phone to my car for carplay. I just leave it plugged into the usb port (without the phone) when I'm not in the car. Do you think it's slowly draining some energy from the car battery?

[–] [email protected] 9 points 11 months ago* (last edited 11 months ago) (1 children)

The cables themselves do not use power. It is the brick.

Your radio being off would not push any power through a cable. Also your cigarette lighter being off would not push any power. Which is why plugging it in won't do anything.

To continue the metaphor - your water is turned off. You can't use up water that isn't there.

The reason the brick uses power is because it is available 24/7 for you to plug something in - and when you do - it can ask that device how much power it wants - does it have fast charging? Etcetera.

[–] [email protected] 3 points 11 months ago* (last edited 11 months ago) (1 children)

Thanks. About the cigarette lighter - my dashcam plugs into it but I always unplug it before I turn the car off so never noticed if the camera turns off along with the car. If it does, does that mean I can just keep the dashcam plugged in and it won’t draw power even though the camera is connected on the other end? Or does closing the circuit mean it will start drawing power?

[–] [email protected] 3 points 11 months ago

If the camera turns off when you turn the car off then you're safe to keep it plugged in.

[–] Kethal 2 points 11 months ago* (last edited 11 months ago)

The water analogy is perfectly fine for many situations, but the reason these don't draw a lot of power when nothing is plugged in isn't because a "valve is off". There's a transformer, so this is like two separate water lines. If the charger is plugged in, there's always a closed circuit on the mains side of the transformer, even if there's an open circuit on the DC side. See the first diagram here: https://circuitdigest.com/electronic-circuits/ac-to-dc-converter-circuit-diagram.

The reason new chargers don't use as much power with no device attached is because of better design. If you checked an old charger or some crappy power supply, they'll use a fair bit of power even with nothing on the DC side. It's not enough that one would matter, but it is enough that there was an industry wide initiative to reduce phantom load resulting in new chargers that use almost nothing when nothing is on the DC.

[–] [email protected] 32 points 11 months ago

They do consume a tiny little bit. I have a Measurement thingy that yoj plug between your outlet and whatever is plugged in which is accurate to 0.1 W. I tryed 3 chargers, one shows 0.1 W, the other two show 0.0 . I still know they consume a tiny bit, but less than 0.1 W is almost nothing. 0.1 W would come out to a consumtion of 0.876 kWh over a year, wich costs me 0.30 €.

[–] [email protected] 24 points 11 months ago (2 children)

A good rule of thumb is that the energy needs to go somewhere. So if the adapter was drawing a significant amount of power, it would get warm to the touch.

[–] stevestevesteve 3 points 11 months ago

That's true - And with a halfway decent thermal camera, you can see most of these unused chargers as "hot" spots. They're so low power that they're only slightly above ambient, but still something the cameras can see.

[–] [email protected] 3 points 11 months ago

That's how I found out that my desktop speakers consume power even with the physical button being off and status light dark. The power brick stays warm indefinitely, a good 20W feels like! I have to unplug that thing now when not in use. Any normal power brick will be <1W of course.

[–] [email protected] 17 points 11 months ago (1 children)

My office when everything is off consumes 7w total.

That's 2 high end computers, 3 monitors in sleep mode, 2 phone chargers a laptop charger.

7w is more than tolerable for me

[–] [email protected] 11 points 11 months ago (1 children)

Yeah both the monitors and computers will consume a bit. Even a modern PC when turned off is in a type of deep sleep mode, for stuff like wake on LAN.

The chargers will hardly even register anything, except maybe in some rare case where its a special one that is doing some sort of passive listening (like the PC's)

[–] [email protected] 6 points 11 months ago (1 children)

I think my monitors are rated at 0.5w each

I actually think the biggest drain are the power strips with built in USB adapters. Maybe 1w each

[–] [email protected] 1 points 11 months ago

A funny culprit I found during my own investigation was the GFCI bathroom outlet, which draws an impressive 4W. The status light + whatever the trickle current it uses to do its function thus dwarfs the standby power of any other electronic device.

[–] [email protected] 13 points 11 months ago (1 children)

https://en.m.wikipedia.org/wiki/Standby_power

You can always get a Kill-a-watt (or similar if those aren't available for the EU) to see how much power something uses in standby

I remember there being special power strips you could get to detect and stop phantom loads like this. But according to that article, there are now regulations to keep this power draw low, so it's probably not a major problem with modern devices.

[–] [email protected] 7 points 11 months ago

i have a couple of those power strips at the office. i'm always forgetting about that 'feature' and end up with stuff 'mysteriously' shutting-off or draining battery instead of charging.