This just an ideea to for the PSU manufacturers for home users
A small battery included in the PSU for 5-10 min self-sufficiency(self recharge)
5-10 min its enough to save importance files and to close properly windows without damaging the software or the hardware..maybe i'am in a overclocking procedure..or in a game i need to save etc etc...anyway when the energy is cut for 30/sec all the downloads/install/defrag is compromise.Is not happening every day but 1 time at 6months is enough to make damage if you are in an serious thing...

Get a UPS is you are worried about it. The weight of the battery alone would prevent me from wanting it.

Aside from that, I think it would be cost prohibitive to include. And, what about the monitor? You need to be able to see to shut down, unless you send a signal from the PSU to the machine that power is out and it needs to initial a shutdown.

It will not be heavy/big or expensive.
A car battery is not so big/it is heavy and its provide energy for at least 2 years!!!
For a PSU it will be small and light and will provide enough energy for enything for 5-10 min when is needed(including a connection with the monitor)
Its not so difficult or impossible

Yeah, they have those now. They are called UPS's. Do you know how heavy they are?

The problem is that you have to now communicate between the motherboard and the PSU. So the PSU is going to need some limited logic for that as well as the power circuitry to generate a sinewave from the battery power, just like a UPS does. The battery will need to be replaced periodically, and it is going to be heavier than you think. Go pick up a UPS battery and you'll see what I mean, and it doesn't even have to be a big battery. I just replaced 6 of them so I know.

I never said it was difficult, nor impossible. I said it was impractical.

Ok.ok...but everything needs to be improved.
I think at this battery to be self-recharge and very light..but i think there is not so much interest on this product to take a deep research

Sure, everything needs to be improved, and most things are, in time. Li-ion batteries used in most laptops today took over 10 years to develop. One day you may see what you are suggesting. We already have Laptops with batteries, right? Sort of the same thing, but a desktop system requires a lot more power, and now you want to throw in power to the monitor too, which could be several amps.

There's a reason why some things are left seperated: Sometimes they work better that way.