byza :
The battery out of a campervan and a device that converts power from DC to AC. Like those plugs that you can plug into a cigaret lighter in the car to plug in laptop power cords, but this one would hook up straight to the battery. If you do go for this option make sure you go for a pure sine wave inverter, you definitely don't want to end up with a square wave inverter. The problem with this setup is I don't see how you're going to be able to put it on an automatic switch to kick in when the power goes out.
What is your build? Just because you have a 1300w PSU doesn't mean you're going to use 1300w. Also, where are you that the power goes out for an hour regularly enough to warrant needing a UPS to power it for that long?
Specs:
AMD Athlon X4 760K (OC'd to 4.6GHz)
MSI A88X G45 Gaming FM2+ ATX Motherboard
PNY XLR8 1x8GB 1866MHz
MSI Twin Frozr GTX 760 4GB (OC'd to 1.26GHz)
Cooler Master V8 GTS
Cooler Master Enforcer
Rosewill Lightning 1300w 80+ Gold Certified
Mushkin Enhanced Chronos 480GB SSD (C:\ Drive)
Kingston SSDNow V3 120GB SSD (H:\ Drive)
Seagate 1TB HDD (D:\ Drive)
I am planning to have some more RAM, SSD storage, and switch to Intel (5820k or 4970k or wait for Broadwell). And go SLI with either 760 4GB (OC'd), GTX 880 (if the performance is superior to the 780 Ti), or GTX 980. (If I'm really going to wait).