A network closet without a UPS is one flickering streetlight away from a hard crash. Power in Australia is mostly good — until a storm, a substation fault, or someone in the building trips a breaker. A correctly sized uninterruptible power supply lets your gear ride through short blips and shut down cleanly on longer ones, instead of dropping the whole network mid-transaction.
Sizing a UPS is not guesswork, but it is easy to get wrong by reading the wrong number on the box. Here is the honest method.
What a UPS actually buys you
Two different things, and you should know which you are paying for:
- Protection — clean power through sags, surges and brief dropouts, so equipment is not stressed or corrupted.
- Runtime — minutes of battery to either ride out a short outage or perform a graceful, automatic shutdown.
More battery buys more runtime, not more protection. Decide whether you need “ride through a 2-minute blip” or “stay up for 30 minutes” — it changes the model.
VA vs watts — the number people get wrong
UPS units are advertised in VA (volt-amps), but your gear draws watts. They are related by power factor; modern IT loads sit near 0.9, so a 1000VA UPS realistically supports about 900 W. Size against both ratings and against whichever your load reaches first. Quoting only VA is how closets end up under-protected.
Size it in five steps
- List everything the UPS must protect — router/modem, firewall, core and PoE switches, any on-prem server or NVR.
- Add up the real wattage — use actual draw, not the PSU maximum.
- Decide how long you need to run — minutes for a clean shutdown, or longer to ride through outages.
- Convert watts to VA and add headroom — watts ÷ 0.9, then +20–30%.
- Match a model and check the outlets — right VA/W and runtime, correct outlet type and count, and a management card if you want remote shutdown.
Topology and form factor
| Choice | Best for | Trade-off |
|---|---|---|
| Line-interactive | Most network closets | Excellent value and protection; a brief transfer time that IT gear tolerates fine |
| Online (double-conversion) | Sensitive loads, dirty power | Always-on isolated sine wave; costs more, runs warmer, uses more power |
| Desktop / tower | A small closet or a couple of devices | Tidy on a shelf; not rack-friendly |
| Rackmount | A comms rack | Fits the rack and scales runtime; needs the rack space (U) |
For the overwhelming majority of SMB closets, line-interactive is the correct, cost-effective answer. Reserve online double-conversion for genuinely sensitive equipment or known-bad power.
Don’t forget
- Batteries age. Plan replacement every 3–5 years (sooner in a hot closet) — a flat battery means zero protection.
- Get a network management card so the UPS can alert you and trigger an automatic, graceful shutdown of a server.
- Check outlet type and count — most IT gear uses IEC C13; make sure there are enough, and that the input plug suits your AU 10A outlet.
Recommendations
- Small closet (router, firewall, one switch): a 750VA line-interactive UPS.
- Typical closet (PoE switch, a couple of APs, modem/router): 1000VA for comfortable runtime and headroom.
- Full comms rack (PoE switches, a server, longer runtime): 1500VA rackmount.
Australian specifics
A UPS is also the unsung hero of internet failover — an outage is often power and internet at once, and a dead modem can’t fail over. Prices are GST-inclusive, warranty and ACL cover sit with us, and availability is shown honestly: if a model is on supplier ETA rather than verified on hand, you will see the real date and can choose the in-stock size instead. For a rack build, add the UPS to a quote alongside your PoE switch and we will confirm runtime and stock.
