Uninterupted Power supply

i would be looking at something around 1300va/780w at minimum.

i have an apc xs1300 (same specs as above) and i'm running an i7-920 gtx470 machine on it with an older lcdtv and at idle i can get about 10 minutes of use. at high load this figure drops to 3-4 minutes

the size of your psu doesnt matter. what matters is the actual draw of your pc. for instance i have a 1000w psu however at idle my pc draws only about 140w but can draw 400w at load. my monitor draws about 230w. i have my soundsystem hooked up to a different system.

if you have an average gaming system with decent cpu and decent level gpu then i would say that with a ups similar to the one i use you should get between 12-14 minutes of pc use at idle/web browsing/basic activities. under heavy load such as in game i would estimate about 5-6 minutes maximum.

is that 915 just for the pc? or does that count the monitor and speakers in it?

also list what voltage your electricity is in your country (i saw that link said india)

please read the entirety of my post...

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with monitors that puts you at a theoretical minimum of 355w and a maximum of 1020w

now your minimum usage numbers arent a problem however the maximum numbers could very well be a problem.

a 1500va/980w battery backup such as the one below can last for about 40 minutes at minimum however your maximum is outside its maximum (980w) specifications. the one you linked me to is even worse at only a 865w peak. if you lose power and the system is under full load the ups will not be able to power the load and your system will suffer a shutdown as if you had no ups.

that means that if you have all 3 monitors, speakers and tower plugged in to your battery backup it will not work when under full maximum load. now, if you are not at full load (under the max wattage) then it would work. please see my notes about full load below the line...

a 2200va/1980w battery backup (the next step up) can last for about 100 minutes at minimum and 23 minutes at maximum without issues. you dont need to worry about full load at all in this case. however, its not cheap.
http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SUA2200I&total_watts=1000

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for the 1500va ups systems... if you ran at the maximum supported wattage of the system i listed (980w) you would get about 6 minutes of runtime. if running the system you mentioned (885w) you would get 2.5 minutes of runtime. keep in mind that if you exceeded those values the system would not work at all.

now, with all that said even running a full system burn in test you arent going to go to full load (max draw) conditions. the 885w (without speakers) that you listed sounds very high even for a system with a r9 290x and 4770k. i'm betting that you dont come anywhere NEAR that during actual daily use.

just as an example my system lists at a peak load of 539w at 100% load when calculated out using http://extreme.outervision.com/PSUEngine however my actual normal maximum wattage is anywhere from 340w-430w while gaming. so even though you want to keep the theoretical maximums in mind... your ACTUAL maximum wattage used is more important.

now, if your actual wattages used are below the rated maximums on the ups then you wont have a problem.

if your actual values are below 885w then the one you linked would work. you wouldnt get 10 minutes of use though.

if your actual values are below 980w then the one i linked would work. you will get 10 minutes of use if your max actual watts used is about 800w

if your values ever exceed the max rated capacity though... well you know what happens.

now, you could not put your speakers on the ups and perhaps put only 1 monitor on the ups (or just have them on the surge protect side not the battery backup side) and that would drop you by a good 100w which would extend your runtimes

keep in mind that your actual use depends on the wattage drawn by the system at the time. if running at minimum draw (idle or surfing the web) your runtimes will be much longer. above i am discussing the minimum runtimes (at maximum wattages).

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if you have any questions.. post them.

i know its a bit confusing.

ah..... so you have TWO r9 290x. that explains thet rather high numbers that you have. you can ignore what i said about your numbers looking two high as i thought you were using just one card (since you did not state two).

well technically something with 1100w would start up and power your equipment (however not for any more than a few minutes). you want something larger than your draw to actually give you time to shut down or wait out a short power blackout.

the next size up made by apc is the 1980w/2200va model i linked above. they have nothing in between the 980w/1500va model and that or i would have suggested it. the 1980w model can power your system for about 20 minutes at "maximum draw" which is great however its not cheap at all.

thats the problem with battery backups and gaming computers. ones which give you the runtime you need are NOT cheap.

you can do as you wishbut i would get something with at least 1500w to give yourself some runtime (hence why i suggested the 1980w version)

as an alternative, you can do something similar by using some car batteries, a charging system and an inverter. its ugly as sin however a rack of batteries can be charged by a solar panel and can even power a whole room if you have enough batteries. depending on prices it might even be cheaper than a ups to go with a few batteries and said equipment. that isnt something you want sitting on your desk though! (unlike a ups)