Guys i need help choosing an UPS, i never bought one so i don't know what i should be looking at when buying an UPS, the ups will be use for my current pc.

Meanwhile i'll be on google looking for more info, thanks.

 

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Gigabyte GA-Z77X-D3H, Intel i5 3570k,  2x4 GB Kingston, XFX HD 6870, Seasonic M12II 850W, Windows 7 Ultimate x64, Seagate 500GB, Seagate 2TB

Most importantly you want a Line Interactive model, what that does is constantly monitor the line condition, boosting up the level during a brownout and switching to the battery if line voltage exceeds a certain amount, while not running on the battery 24/7 (which would be an Online UPS, intended for servers and hospitals), and having a very fast switchover (compared to a Standby model, which can have a switchover time in excess of your PSU holdup time). Also, make sure it is a Pure Sine Wave UPS, as square wave (also called Simulated Sine Wave) can cause damage to components, I blame mine for blowing my last PSU. Now they're common and not much more expensive than the square wave models.

Now comes the most important part: size. If you can afford a 1000w then get it, as it will allow for future expansion, compensate for battery life degeneration over time, as well as give a longer run time.

Also important is the brand you use. CyberPower, TrippLite, and APC are the big three. Of those, CyberPower models are the most affordable, especially their pure sine wave models (I run two, unfortunately not pure sine wave but guess what I'm going to get soon , a 900w for my computer and 600w for my TV/DVR/Bose Wave Radio/Satellite Receiver). Before this I had an Ultra brand 600w and it...well...Let's just say I won't buy one again.

But UPSs have come a long way in the past couple of years, most even have an LCD display with diagnostic and other information such as in/out voltages, battery level and runtime, and load level, and all have a very high dollar connected equipment guarantee.

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Crosshair IV Formula, Phenom II x4 965 w/ Corsair H60, 8 GiB OCZ Platinum DDR3 1600, XFX HD 7970 Ghz, 512GB Vertex 4, 256GB Vector, 240GB Agility 3, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, HP ZR2440w, Win 7 Ultimate x64

First, square wave won't damage anything over the few minutes it will be in use in the event of a power failure.  Sine wave is better if the price works, but it will always be more expensive.

Second, don't get confused between W and VA.  A 1500VA UPS does not provide 1500W of backup power.  I have in this room two 1500VA units that supply up to 865W of power and one 1500VA unit that supplies up to 980W.  At my office, I have two 1500VA units that supply 1440W each.  The difference is battery voltage - 24V, 36V, and 48V nominal, respectively.  So if you don't see power capacity explicitly listed, look for battery voltage - the higher the voltage, the higher the capacity.

I agree that line interactive with AVR is much better than standby.  In the event of over or under voltage, a standby unit either does nothing, or switches to battery, so you're discharing and charging constantly for the duration of the out-of-bounds power situation.  That shortens the life of the battery significantly.  AVR in a line interactive unit uses transformers to boost low voltage or reduce high voltage, without touching the battery.  If the variation is too high, such units will all fall back to the battery.  The specs should show how much they can handle before doing that.

A UPS described as "online" is the best way to get very clean power for sensitive equipment, as the incoming AC power is converted to DC, then back to AC, which makes the output absolutely consistent.  Such units are quite expensive, and completely overkill for a computer.  The switching power supplies found in PC's can handle quite a lot of input variation - almost all currently sold can operate at any value between 100V and 240V (and work more efficiently at higher voltages).

Given where you're posting this question, it's a safe bet the UPS is for a gaming machine.  Given that, I'd recommend jumping straight to a 1500VA unit, which won't shut down in a panic a few seconds after the power goes out should you happen to be in a game sucking up a lot of juice.  That also gives you spare capacity to plug in things like a router, switch, cable modem, etc.

The brands I'd recommend, in order, are Tripp-Lite, APC, and then CyberPower.  That's pretty much descending price order as well, for roughly feature-equivalent units.  Make sure whatever you get has user-replaceable batteries, and be prepared to replace them in about three years.  You do not want to think you're safe only to have the UPS quit immediately after the power fails because the battery is shot.