[SOLVED] UPS (Uninterrupted Power Supply) Wattage Requirement for 1200W PSU?

handsomep

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If my computer's PSU is 1200W (Corsair AX1200), would that mean I'd need a UPS that was 1200W? I realize that the 1200W is the capacity of the PSU and not the load, but I was just wondering whether at startup (or similar) the wattage rating of the PSU might be relevant in selecting a proper UPS? Whilst running, the total load of my computer and peripherals (including PSU of course) is only 240W.

Thank you!
 

Aeacus

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When looking for an UPS, there are 2 things to look out:
  1. Output waveform (square wave, simulated sine wave and true/pure sine wave)
  2. Design (stand-by, line-interactive and online)
From here you can read about the differences between output waveform,
link: https://www.kstar.com/indexproblem/17355.jhtml

And here are explanations about the UPS design,
link: https://www.eetimes.com/document.asp?doc_id=1272971

Waveform and design
For PCs, line-interactive UPS would be more than enough since PSUs can easily handle the 2ms to 5ms transfer time of line-interactive UPS.
As far as output waveform goes, true/pure sine wave UPS is best used. While simulated sine wave UPSes are cheaper than true/pure sine wave UPSes, PSUs with Active PFC aren't compatible with simulated sine wave. You might get simulated sine wave UPS running with Active PFC PSU but there can be some major issues. Here's what, how and why.

How do you know which PSUs have Active PFC and which ones don't?
Simple, every PSU that has 80+ certification (e.g 80+ Bronze or 80+ Gold) has Active PFC.

What is Active PFC?
Further reading: https://en.wikipedia.org/wiki/Power_factor#Power_factor_correction_(PFC)_in_non-linear_loads

What can happen when using simulated sine wave UPS with Active PFC PSU?
When simulated sine wave UPS switches over to the battery power, one of 3 things can happen:
  1. UPS displays error resulting PC to shut down immediately.
  2. UPS shuts down resulting PC to shut down immediately.
  3. UPS switches to battery power resulting PC to power off from UPS (PC stays on).
Why it happens?
Simulated sine wave UPS produces a zero output state during the phase change cycle resulting in a power “gap”. This gap may cause power interruption for active PFC PSUs when switching from AC power output to simulated sine wave output (battery mode).

What to do next?
As stated above, your PC can run off from simulated sine wave UPS but be prepared when you face issues with it. When issues do rise, your best bet would be returning the simulated sine wave UPS and getting true/pure sine wave UPS. Or you can go with true/pure sine wave UPS off the bat.

Wattage
As far as UPS wattage goes, you need to consider the power draw of your PC and monitors. Maybe speakers and wi-fi router too if you plan to plug those into the UPS as well. Though, printers, scanners and other such hardware (full list on your UPS manual) don't plug to the UPS since their startup power draw is way too much for UPS to handle and you can fry your UPS.

Taking PSU's max wattage as a baseline is good idea since it will give your UPS more headroom and you can get longer runtime out of your UPS. Since your PSU is 1.2 kW, it is nowhere near to the actual power consumption of your PC. Hence why i asked your full system specs, so i can calculate how much power it consumes.
Once that is known, at least one monitor is added on top of it. Depending on the monitor size, they use between 23W to 52W. For more accurate power consumption, i need to know your monitor make and model so i can look up it's power consumption. Wi-fi routers don't consume much power. For example, my Cisco EPC3940L consumes 12V at 3A which means 36W.

Good UPS brands to go for are CyberPower, TrippLite and APC. While there are other UPS brands as well, those three are the best out there.
Note: The more powerful UPS you have, the longer UPS can keep your PC running before it's battery is empty.

To suggest an UPS for you, i need to know your full system specs + monitor make & model (or part number) + any other piece of hardware make & model you're planning to plug into UPS. Also, i need to know your location (e.g USA, Germany, Italy, Australia etc) so i can suggest UPS with correct power sockets.

Btw, you can take your PSU max wattage as a baseline and add other hardware to it. At my rough estimation, when including PSU max wattage (1.2 kW), you can look towards 1500VA/~1350W UPS. With that powerful UPS, your PC runtime off the UPS is considerable (40 mins or so) but in turn, that powerful UPS will also cost you a lot of money, money which you could save if your PC power consumption would be calculated, to result in a smaller (better suited according to the power consumption) and cheaper UPS.
 
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Aeacus

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Why do you have 1.2 kW PSU in there when the total load on your PSU is 1/5? You do realize that this gives your PSU terrible efficiency, right? Since PSUs are most efficient when load on them is between 50% and 80% of their total wattage output.

In any event, what's your full system specs?

And when it comes to UPS selection, there is far more to it than just PSU max output wattage, which i can share in my next reply.
 

handsomep

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Why do you have 1.2 kW PSU in there when the total load on your PSU is 1/5? You do realize that this gives your PSU terrible efficiency, right? Since PSUs are most efficient when load on them is between 50% and 80% of their total wattage output.

In any event, what's your full system specs?

And when it comes to UPS selection, there is far more to it than just PSU max output wattage, which i can share in my next reply.
I wasn't aware of that no. It was a dual loop liquid cooled machine with two radiators when I purchased it, but I've since converted it to a single loop with one radiator. I wasn't really sure what size PSU I needed when I purchased the computer several years ago, but wanted to be on the safe side. I guess I figured bigger was better. I can dig up my system specs if you like, but mainly I wanted to know what the requirement would be for a UPS just for the 1200 PSU. During normal operation, obviously it's not pulling 1200W (the system as a whole only has a load of 240W) but I just wasn't sure whether on bootup (and/or coming out of hibernation) if the PSU had a higher wattage and whether that was at all relevant in terms of the UPS.
 

Aeacus

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Ambassador
When looking for an UPS, there are 2 things to look out:
  1. Output waveform (square wave, simulated sine wave and true/pure sine wave)
  2. Design (stand-by, line-interactive and online)
From here you can read about the differences between output waveform,
link: https://www.kstar.com/indexproblem/17355.jhtml

And here are explanations about the UPS design,
link: https://www.eetimes.com/document.asp?doc_id=1272971

Waveform and design
For PCs, line-interactive UPS would be more than enough since PSUs can easily handle the 2ms to 5ms transfer time of line-interactive UPS.
As far as output waveform goes, true/pure sine wave UPS is best used. While simulated sine wave UPSes are cheaper than true/pure sine wave UPSes, PSUs with Active PFC aren't compatible with simulated sine wave. You might get simulated sine wave UPS running with Active PFC PSU but there can be some major issues. Here's what, how and why.

How do you know which PSUs have Active PFC and which ones don't?
Simple, every PSU that has 80+ certification (e.g 80+ Bronze or 80+ Gold) has Active PFC.

What is Active PFC?
Further reading: https://en.wikipedia.org/wiki/Power_factor#Power_factor_correction_(PFC)_in_non-linear_loads

What can happen when using simulated sine wave UPS with Active PFC PSU?
When simulated sine wave UPS switches over to the battery power, one of 3 things can happen:
  1. UPS displays error resulting PC to shut down immediately.
  2. UPS shuts down resulting PC to shut down immediately.
  3. UPS switches to battery power resulting PC to power off from UPS (PC stays on).
Why it happens?
Simulated sine wave UPS produces a zero output state during the phase change cycle resulting in a power “gap”. This gap may cause power interruption for active PFC PSUs when switching from AC power output to simulated sine wave output (battery mode).

What to do next?
As stated above, your PC can run off from simulated sine wave UPS but be prepared when you face issues with it. When issues do rise, your best bet would be returning the simulated sine wave UPS and getting true/pure sine wave UPS. Or you can go with true/pure sine wave UPS off the bat.

Wattage
As far as UPS wattage goes, you need to consider the power draw of your PC and monitors. Maybe speakers and wi-fi router too if you plan to plug those into the UPS as well. Though, printers, scanners and other such hardware (full list on your UPS manual) don't plug to the UPS since their startup power draw is way too much for UPS to handle and you can fry your UPS.

Taking PSU's max wattage as a baseline is good idea since it will give your UPS more headroom and you can get longer runtime out of your UPS. Since your PSU is 1.2 kW, it is nowhere near to the actual power consumption of your PC. Hence why i asked your full system specs, so i can calculate how much power it consumes.
Once that is known, at least one monitor is added on top of it. Depending on the monitor size, they use between 23W to 52W. For more accurate power consumption, i need to know your monitor make and model so i can look up it's power consumption. Wi-fi routers don't consume much power. For example, my Cisco EPC3940L consumes 12V at 3A which means 36W.

Good UPS brands to go for are CyberPower, TrippLite and APC. While there are other UPS brands as well, those three are the best out there.
Note: The more powerful UPS you have, the longer UPS can keep your PC running before it's battery is empty.

To suggest an UPS for you, i need to know your full system specs + monitor make & model (or part number) + any other piece of hardware make & model you're planning to plug into UPS. Also, i need to know your location (e.g USA, Germany, Italy, Australia etc) so i can suggest UPS with correct power sockets.

Btw, you can take your PSU max wattage as a baseline and add other hardware to it. At my rough estimation, when including PSU max wattage (1.2 kW), you can look towards 1500VA/~1350W UPS. With that powerful UPS, your PC runtime off the UPS is considerable (40 mins or so) but in turn, that powerful UPS will also cost you a lot of money, money which you could save if your PC power consumption would be calculated, to result in a smaller (better suited according to the power consumption) and cheaper UPS.
 
Reactions: Ralston18

handsomep

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Nov 19, 2007
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Btw, you can take your PSU max wattage as a baseline and add other hardware to it. At my rough estimation, when including PSU max wattage (1.2 kW), you can look towards 1500VA/~1350W UPS.
So you're saying that a 1200W PSU would requre a 1200W UPS on it's own? The PSU and everything else combined has a load of only 240W. I called Corsair when I purchased this computer and was looking at UPS options and even they didn't really give me a definitive answer about what kind of wattage the PSU pulled at bootup... And I wasn't sure if that was even relevant. I mean it's not like you're going to boot up a computer during a power failure right? Anyway, I ended up plugging my specs in and looked for something that would run about 40 minutes or so in a power failure and purchased APC Smart-UPS X 1500VA. I had owned previous smaller APC UPS's (for smaller computer builds) before and was happy with them. The unit is telling me to replace the battery (can't complain, it's lasted 7 years), but it's $400 for the battery vs $200 for a brand new CyberPower CP1500AVRLCD so I was considering my options.
 

Aeacus

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I called Corsair when I purchased this computer and was looking at UPS options and even they didn't really give me a definitive answer about what kind of wattage the PSU pulled at bootup...
During boot-up, PSU doesn't draw much power from the wall. It's all other components combined that makes answering your question difficult. And without full system specs, i can't even estimate that.

Hardware manufacturers know the start up peak power of their hardware, but they haven't disclosed that to the public. So, unless someone specifically tests it, we don't know. And even when tested, it is accurate to that specific hardware. It's not like where i test my GPU, MSI GTX 1660TI Gaming X and my findings can be used with all GTX 1660TI GPUs out there. No, my findings would only be suitable for that specific make and model GPU.

APC Smart-UPS X 1500VA
A good choice of UPS. :) With it, you'd easily get 30+ mins of runtime out of it.

Btw, i'm running two of these myself: CyberPower CP1300EPFCLCD.
 
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handsomep

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Btw, i'm running two of these myself: CyberPower CP1300EPFCLCD.
Yeah, if I was starting fresh, I'd probably lean towards a much more affordable (yet still very reputable) CyberPower UPS. Since I've already invested in the APC shell, I figured I'd just get the replacement battery even though a brand new CyberPower UPS would be just over the half the price of the APC replacement battery. I'm not sure when I bought my UPS back in 2011 that CyberPower was around and/or established as it is today. But the APC battery lasted 7 years which is very good and their customer service was also very good.
 
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mikewinddale

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Your PSU's draw is determined by the components (CPU, GPU, etc.), not by the PSU's max load.

A 1200W PSU means it can supply 1200W without exploding or burning. But the PSU won't draw 1200W unless the components do.

Ultimately, electricity is pulled, not pushed, so to speak. It's your components that pull electricity from the wall. They'll pull as much as they want, no matter how much that is, and if they pull more than the PSU can handle, the PSU will burn or explode (or shut down and cut the connection to save its own life).

If your system uses 240W, then that is the number that is important.

Personally, I'd get a CP1500PFCLCD, which is rated to supply up to 1000W. Above that, and the price begins to skyrocket. Most consumer UPSes top out at 1500VA, which is 900 to 1000W, and above that, you need enterprise-grade.
 

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