Power cuts in Singapore are rare, but they do happen, and short voltage dips and surges are far more common. A UPS sits between the wall socket and your equipment so that a dip does not reboot a switch mid-day or corrupt a NAS volume. Picking one comes down to three questions: which topology, what size, and how much runtime.
The three UPS topologies
| Type | How it works | Best for | Examples |
|---|---|---|---|
| Standby | Passes mains power through; switches to battery when power fails | Single desktop PCs, home office | APC Back-UPS |
| Line-interactive | Adds automatic voltage regulation (AVR) that corrects dips and surges without using the battery | Network racks, small servers, NAS, most offices | Back-UPS Pro, Smart-UPS SMT, SMX |
| Online (double conversion) | Converts all incoming power to DC and back to clean AC, so equipment never sees the mains directly; zero transfer time | Critical servers, storage, labs, sites with poor power quality or generators | Smart-UPS SRT, Easy UPS On-Line |
Our rule of thumb: line-interactive is right for most office network and server racks. Choose online double-conversion when downtime is genuinely expensive, when equipment is sensitive to any transfer gap, or when the building's power is noisy, such as in industrial units or sites with a backup generator.
Sizing: VA, watts and headroom
UPS units are rated in both VA (volt-amperes) and watts. Watts is the number that matters for modern IT equipment. To size a UPS:
- List every device that will plug into it: servers, NAS, switches, firewall, router.
- Add up their actual power draw in watts. Use the datasheet's typical or maximum figure, or measure with a meter, not the power supply's rated maximum.
- Aim for a UPS whose watt rating is 25 to 40% above that total. Running a UPS at 60 to 75% load leaves room to grow and gives more runtime.
Example: a rack with a small server (250 W), a 4-bay NAS (60 W), a PoE switch feeding access points (180 W) and a firewall (30 W) totals about 520 W. A 1500VA unit rated around 1000 W or more, such as the APC Smart-UPS 1500VA 2U rackmount, would run at roughly half load. For a fuller walk-through, see our UPS size calculator guide.
Runtime: how long do you really need?
A UPS is not meant to keep the office running through a long outage. Its job is to ride through short dips and give servers time to shut down cleanly. For most offices, 10 to 15 minutes at actual load is enough. If you need longer, choose a model that accepts external battery packs (common in the SRT and SMX ranges) rather than oversizing the UPS itself.
Automatic shutdown is essential
Runtime is wasted if nobody is there to shut the servers down. Connect the UPS to your equipment over USB, or add a network management card such as the APC Network Management Card 3 (AP9640), so servers, hypervisors and NAS units shut down gracefully when battery runs low. Most business NAS units, including Synology and QNAP, support UPS-triggered shutdown natively.
Batteries and Singapore's heat
Valve-regulated lead-acid UPS batteries typically last three to five years at around 25°C, and heat shortens that sharply. A UPS in an unventilated cabinet or a store room without air-conditioning will need new batteries much sooner. Keep the UPS in a cool space, run the self-test regularly, and plan battery replacement in the IT budget. We stock the APC replacement battery range and Eaton UPS batteries.
Rackmount or tower?
If you have a server rack, use a rackmount or rack/tower convertible model so it sits in the rack with proper cable management. Rack units also tend to have hot-swappable batteries. For a single NAS or a network cabinet on a shelf, a tower unit is simpler and cheaper.
Frequently asked questions
Can I plug a laser printer into a UPS?
No. Laser printers draw large current spikes when warming up and can overload a UPS. Use a surge protector for printers instead.
What is the difference between APC and Eaton?
Both make reliable line-interactive and online ranges with network management options. Choose on price, form factor and your existing management software. See our Eaton UPS and APC UPS ranges.
How often should I test the UPS?
Run the built-in self-test monthly and do a controlled runtime test once a year, outside office hours.
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