Keep power supply conneted to the outlet 24/7 or not?

Hello friends. Recently this question sparked into my mind out of nowhere (yeah, like the Randy Horton meme): do power supply in general get damaged if they're constantly connected to an outlet even without any load applied to them? I know this can happen to desktops power supply but I couldn't find the answer online regarding things like laptop power supply and USB chargers. My personal idea is that what applies for the desktop PC's power supply applies for those chargers aswell. Thanks for opening the topic and for the answer (:

Power supply's don't get damaged unless cheaply made (they usually ignite in fire), but leaving USB adapters always plugged in without charging is just pointless (and costs money for energy).

What gets damaged if you let a battery constant to the power supply they need to discharge to 0% once in a while. (maybe somebody else can help me here but i hear there are some new battery's that need to be powered between 20-80% for life time)/

Well yeah, that's what I already known really. And I know something about batteries too. Thanks for the answer anyway.

Yeah sorry i couldn't answer that it would open secret portals to other dimensions and its best not to do it because demons will take over our world. :p

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Please don't do that. You may brick the battery this way. Well, usually you won't be able to do this anyway because battery controller won't allow it for exactly this reason (when you see "0%", there's actually some juice left), but if there's, say, an error in microcode, you may accidentally succeed at bricking the battery - irreversibly.

Regarding power supplies - yep, nothing serious can happen, but you're wasting electricity. Without load on a secondary winding, transformer's primary winding basically works as a heater, I guess.


Depends what battery right?

@dmj Thanks for the answer.

@The_Cable Only Ni-Cd batteries that had memory effect had to be totally discharged. But since the Ni-Mh/Li-Ion batteries were introduced that practice only do damages to the battery.

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No never. You should never discharge a battery past a certain level if it is rechargeable.

I know only one exception: if your battery controller's software is already screwed up and your laptop/smartphone switches off while still showing, like, 30% charge left. Then yes, you may need to turn it on again, wait for it to die, turn it on, wait, etc., until it won't even turn on anymore, then plug it in without booting it up and wait for about a day. This gives controller chance to recalibrate. But it's an extreme case scenario.

I though it was for some battery's in the passed that it was better to make them go to 0 once in a while. you now talk about every battery now.

that what @MetalizeYourBrain i knew i also didn't say all battery in my original post.
And he added what battery since i forgot the name of those things.

Guys I don't want to be an asshole or ruin anyone the conversation but we're going a bit off topic aren't we? I appreciate your collaboration.

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No thats cycle charging. You do that to break in a battery. For example your phone to make the battery last longer the longer you have it one should charge it when it gets to about 20%. You should cycle charge it (drain the battery till dead) once a month. When charging you should always go to 100% and as soon as it hits 100% percent you should take it off. That of course is for the best performance over the long run.

@MetalizeYourBrain as for your question unless you have shitty wiring in your house ie the polarity of the wall socket is switched, then no its fine. Its an open circuit. It would be like leaving a a wire in the wall. nothing will happen unless you do something dumb. Like leaving a wire in the wall.


I thought the same really but a power supply is much more complicated than an open circuit. I have the power supply of my printer and an OG white Apple charger 5V/1A, for example, that make some "sounds" when left without any load on them. That's what got me thinking. Thanks for the answer.

If your power supply is plugged into the wall (and not open-circuit via a switch), it will always be using power and creating some DC voltages (3V for PW_ON (green wire), 5V for SB (standby, purple wire)), however, the main 3.3V, 5V, and 12V (high current) rails will be off until PW_ON creates a circuit with ground (via the switch on your case or motherboard). By having it plugged into the wall, the capacitors (normally the main component to fail) inside the power supply will be in use, however, because they are not stressed (only a couple milliamps, if that, in standby), it really won't matter very much for the longevity of the power supply.

What will surely kill a power supply sooner is having it run at/near max recommend load. Example: 500W PSU, with a max recommended of 18A 12V rail continuous load, running near the 18A mark, for long periods of time (gaming). That will kill a power supply much sooner (most likely the capacitors will die first) than by having it plugged into the wall, and is also the reason as to why you should ALWAYS buy a power supply which has a higher power rating than you ever intend to use.


yeah good luck drawing 18 amps from the wall for that long. Power supplies fail bc the caps fail after a certain time. The dielectric just breaks down after awhile and becomes a dead short which is no good. Have no worries. Your house breaker should flip long before you ruin your psu by load and the psu will shut off long before the breaker flips. or at least should.

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They can be damaged if there are line voltage spikes while plugged in. But under normal circumstances? No, they're fine.


PSU's are engineered to be plugged in all the time. It will not harm them.

I have my PC running 24/7 and never turn it off. Not sure if that's good or bad in a consumer part. It been running since 2007 with downtime for upgrades. It the same Case and PSU however


Thanks to each one of you for the answers!

@TheAlmightyBaconLord You won for the most accurate answer (:

Does the same principles apply for other kind of power supply? (Notebook, USB, 12V generic and so on)

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@MetalizeYourBrain All power adapters that I have come across are constantly producing the output voltage (ex. 5V for cell phones, 19V for most laptops). The amount of current travelling through the adapter is tiny (mainly due to resistance), however, they are always powering the output circuitry. I'm not sure whether leaving them in for extended periods of time will affect longeitivty (especially if not in use), you may want to ask that question at the EEVBlog forums, because they are much, much smarter regarding circuitry than I and most forum members here, will ever be.

From my personal experience (worked about 2 years in a computer repair shop, plus at home), I've only really come across about 4 dead power adapters (1 I owned, the other 3 were at the shop). From what I've seen, the power adapters will either produce no output voltage, will produce a lower-than-usable output voltage, OR it will produce the correct output voltage, but under load, the adapter cannot handle the current draw (even if it's the correct adapter for a laptop), deliver varying current's, and the laptop will then just shut-off the power input (not allowing power to flow into the laptop, from the unstable adapter). The last one is what happened to my own power adapter. I personally never attempted to fix the adapter, but I feel as though it would be something simple (an output capacitor probably went bad).

From my experience, I cannot say whether leaving the power adapter plugged into the wall will affect longetivity, and I do not have enough knowledge to give a correct, eduated answer. As stated before, if you really want an answer, some other forum members here might have it, or ask at the EEVBlog forum.

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Thank you so so much for you dedication to answer my question, I really appreciate it. Have a good day (:

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