and no we don't mean United Parcel Service, We mean,
Uninterruptible Power Supply
Please note; This is just a guide and much is in our words.
Many computers these days don't like to be rebooted due to a power fail, servers are a big part as depending on the setup there could be data failures caused by the power, also some of them can take a hour or more to come back online after the power is back.
Any computer tho, is always storing files and so losing power during these times can cause a huge lose in production and also the info that was not saved then too.
To take for example our office, we have redundant UPS for our server tho some services might go down if one fails, but the data on the server will not be lost.
Also just one of our office servers will take 15 min after power is restored (If not on a UPS) before it will even start the software side and this can take another 15 min to come back too, so having just one UPS saves us all this outage, but since our servers have redundant power we also give them redundant UPS and also for longer then a few min our office generator starts up and provides power till the mains returns.
Most UPS also can save a devices from power surges and brown outs which can kill most electronics.
But please take note, there are so many types of UPS on the market and some may not be compatible with some of the systems, but the 3 main types are Standby, Line-Interactive & Online Double-Conversion.
The best in most ways is the Online Double-Conversion, these units cost so much more but are the best for 99% of jobs. Then there is the Line-Interactive and last but not least is Standby.
(As stated by Eaton UPS)
Standby UPS, Protects against power surges and provides battery backup in the event of a power outage. AC power passes through the unit under normal conditions and switches to battery mode when a power failure is detected.
Line-Interactive UPS, In addition to battery backup, line-interactive UPS provide conditioned power, eliminating voltage fluctuations. AC power passes through a voltage regulator, which corrects low and high voltages as needed, and switches to battery backup mode when a power failure is detected.
Online Double-Conversion, the incoming AC power is converted to direct current (DC) and then back to high-quality AC power, free from voltage fluctuations and other distortions common in grid power.
Don't get me wrong as all 3 types have there uses but Online Double-Conversion is one of the best to use.
Standby UPS are OK for non power sentience operations but has a few down sides, the worse is the time it can take to switch to battery, some devices don't like even a flicker in the power and so will shutdown or freeze up, I have even heard of modems being bricked because of the flicker in the power, but note this depends on the UPS too, another note and this depends on the maker but some UPS Standby use square wave and so switching from sign wave to square wave can cause huge problems, So make sure you check what that UPS has.
Line-Interactive UPS, These are in someways almost the same as standby but have so much more functions and protections in them, but of note this all depends on the maker of the UPS, The best to these UPS are they will conditioned the power out going power, they are also the most basic I would install for basic desktop computer.
Then comes the Online Double-Conversion, as stated these are the best in many ways as no matter the incoming power as the outgoing is clean and safe, also devices that don't like a flicker on the power will never see then on these devices.
Yes there are other types but we was talking about the 3 main types here.
Then comes sizing of the UPS, many makers list there UPS size in VA not watts and this makes it hard for people to size there units right, you see the VA is different depending on the power factor of the device and so much more, if you can see a listing in W or Watts its better as it makes sizing the unit so much easier.
Lets say a computer doing normal things like Office 365, depending on the specks of that computer, the computer might have a power of 650W, well you don't get a UPS for 650W as the device might only draw 400W but you also have to include the monitor and other devices that need mains power to run normal, this could put you to 700W on load and so the best to do it get your self a "Plug-in Power Consumption Meter" you plug it all the devices you want to power by a UPS and then load things up to see what its max drain is.
One thing to note, Printers like Laser ones dray huge amounts of power and so are not recommended to be on a ups, even some small laser ones can draw up to 2000W just to start and so if you wanted the printer to be on UPS then you will have to size a unit for that max power size.
Once you have the max power draw I would recommend to almost double it, this way say a computer is drawing a total of 400W and you get a device of 800W it will last longer on batteries and also have power in reserve encase of a upgrade, it also allows the UPS to not be at full load which can also make the UPS not gain high heat loads when it works.
BUT then comes the down side of any UPS.
The batteries, these MUST be replaced ever so many years, some makers state every 2 years and others state 4 years, but this also depends on the battery maker and the use this UPS is in, HEAT is a killer of all devices but also with a UPS short discharges are not good too, this can make the batteries wear quicker.
Like many sites we recommend that a UPS is put on a long load once a year minimum (This is controversial as some makers state other wise) but we state the batteries should be replace every 3 years, but then there is a problems with some UPS on the market, Some of them don't have standard batteries and so it can sometimes cost more to get replacement batteries then the cost of the UPS, there is also some units that have to be completely pulled apart to replace a battery and then you start to get into the right to repair too.
All UPS we install we make sure of the batteries and how to replace them.