If your system will shut down immediately, there is a power outage which can cause loss of unsaved data, you need to get a system that can give you some additional time to get your work in order. If perhaps you are not concerned about the unsaved data getting lost, you may not bother about the Backup power (ไฟสํารองคอม ,which is the term in Thai) as well as spending so much even in keeping in it functioning, although this may not always be the case.
If you use a PC like an iMac, PowerMac or mini-tower, a power outage can turn off your system instantly as it does not have any internal battery.
A PC with an internal battery during a power outage only switches to preserved battery energy. Possessing such a PC helps you maximize data loss scenarios as you can save your documents owing to the time extension provided by the internal battery, except for data being edited on the net.
Importantly, if you own a PC that has lasted up to 4 years, you may not experience the same speed saving your documents. In some cases, the system may shut off automatically regardless of the internal battery as it has lived out its span. A UPS can be advised at this stage.
Should you get another UPS for other devices besides your computer
If you do more work on the net, you can consider getting a Backup power (สำรองไฟ ,which is the term in Thai) like a UPS and connecting your cable, modem or router to it having a functioning ISP. This gives you additional time to save work.
Other devices you can connect to your UPS to retain some power after an outage are: a landline, cordless phone. You can also connect your television or DVD if it takes much time to reload and download your TV programs. Other low power devices (s) can even be plugged to your UPS.