When looking for an UPS, there are 2 things to look out:
- Output waveform (square wave, simulated sine wave and true/pure sine wave)
- Design (stand-by, line-interactive and online)
From here you can read about the differences between output waveform,
link:
http://www.minutemanups.com/support/pwr_un10.php
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:
- UPS displays error resulting PC to shut down immediately.
- UPS shuts down resulting PC to shut down immediately.
- 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.
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.
Here, i need to know how you calculated the 810W? Also, what hardware are you planning to put behind UPS that you need at least 4x output sockets? 1x PC and 3x monitors? Something else? What's the runtime you're looking to get out of the UPS? under 60 sec? 5 min? 15 min? 30 min? And am i correct when i say that you have Schuko (CEE 7/3 sockets and CEE 7/4 plugs) in use?