Power switch on PSU



Lately, I have been switching off the switch on the back of the PSU on my computer after I shut it off. I have been doing this to try and save some energy. Unfortually, I do not know a whole lot about PSU’s or Mobos and I have a couple of concerns.

First, will the battery on my mobo get drained after only a short time? Also, I have noticed that when I switch the PSU back on, it creates a power drain in my room (lights dim). Is it possible to damage my mobo with this surge of energy from the PSU?

Thanks in advance


Whoa… Sounds like you have a lot of gear on one circuit, maybe too much. I notice a power drain when I turn on the amp for my home theater rig, but have yet to see that from power cycling my PC at the switch.

I would suggest not cycling the switch on the back of your PSU. I can’t imagine there being a significant difference in power saving with it switched off. While it’s true the PSU is the first line of defense from surges spikes and other anomalies, theres no guarantee that other components won’t be harmed. Component failure from long-term exposure to those conditions have also been reported.

I guess from my point of view, it just isn’t worth the risk.


As lights are meant to be on a completely different circuit to sockets, I don’t see how turning on a PC should cause that.

When you turn off the PC you are saving power, there is no need to actually switch it off at the PSU switch as it won’t save any more.


When an ATX PSU is in “soft-off”, there is a small power usage for the 5v standby.

If a computer PSU is enough to cause a power dip, I’d say you need to get your wiring checked pretty sharpish.

If you are out in the backwoods with a less than stable supply, it may be more likely - also the older PSU models with no power factor correction may have a rather brutal surge.

After reading some more about it (I always used to turn my multiway switch off every time), now I leave it in soft-off except overnight.

I guess ATX standby power probably supports the CMOS & clock, but the system battery should last 5 years (lithium), or about a month between uses (rechargable).


Maybe my wording was a bit unclear, if it was I apologize.

The “power surge” I was talking about is similar to when a refrigerator switches on. The lights in the room dim slightly for a moment and then return to their normal brightness.

When I turn my PSU on, a similar effect occurs, but it is not as noticable and doesn’t last as long as when the fridge kicks in.


No, I think it was quite clear, at least from my perspective.

Your lights dimming by toggling the switch on the back of your PSU is not a good thing. A modern PC should not draw enough current to cause voltage drop across the circuit. Either you have really faulty wiring as suggested in post #4 or you have too much equipment on one circuit as suggested in post #2. Refrigerators, microwave ovens, stereo amplifiers etc. those are examples of devices that suck huge amounts of current upon power up. PC’s are not.


I would just leave it on. The motherboard doesn’t really use than much power when powered down. It sounds like the wireing in your house/apartment isn’t suficient for the number of items drawing power off it. I had a fire marshal (inspecting the apartments I live in) tell me that it is not uncommon, especially in older buildings, for the wireing to be insuficient for all the electrical devices that people use today. Basically there is too much draw on the wires. You are literally sucking power out of the wires faster than they can deliver power which causes the power to drop momentarilly. You see the same thing with high power car stereo systems. the power demands are so high on a heavy base hit, that the wires delivering power to the amps cannot feed power fast enough, so you use a capacitor (a BIG one) to buffer the power. Your system/power supply takes a lot more power when it first starts up which is what causes it. If it continiouslly pulled that much power it would probably be a fire hazard (though your breakers should trip before that happens). Luckilly it is only momentary. I’m not sure if there is any kind of a capacitor device for household current (I have never heard of one but that doesn’t mean they don’t exsist), but maybe an uninterupted power supply would help buffer the power when it starts. Also be aware, if other high drain devices like your fridge or washer cause this, and your computer is on the same circuit, it can cause stress on your computer. In therory, a power supply is suposed to take care of these power drops and a good quality one can to an extent, but they can only do so much. If there is not enough power then there is not enough power and the power supply cannot create power to even it out (it should have capacitors in it that can do it but only to a limited extent.
An uninterupted power supply has a battery that provides the power to even out power drops. My uninterupted power supplys would trip and go to battery backup momentarilly every time the washer or drier came on. I now have the computer in a diffrent part of the house and on a diffrent power circuit, and don’t have that problem anymore.
An uninterupted power supply might be a good idea, and if moving the computer or maybe running power from a diffrent outlet is an option, then you can hook it up to a circuit that doesn’t have other high drain devices (washer, drier, oven, fridge, airconditioner/heat, home entertainment system etc). Just shut off your circuit breakers one at a time and see what all looses power on each breaker (including the wall sockets). Also, look at the ratings on the various breakers. You may have some circuits in your house/apartment that are designed for more current.

Your power supply has protection from crashing the computer when this happens. The motherboard doesn’t actually power up the system till after a brief delay after the power supply powers up. When the power supply powers up, it waits to detect that power has stabalized and then it sends a power good signal to the mother board letting it know that power is stable. This doesn’t help you if the computer is already on and something else causes the drop in power though.


I’m for the “leave it on, always” approach.
The tiny amount of power that appliances in standby uses isn’t enough for me to bother to plug and unplug them all the live-long day.