Buying a UPS that’s too small leaves you exposed the first time you actually need it. Buying one that’s oversized wastes money you didn’t need to spend. This guide walks through exactly how to size a UPS correctly, step by step.
Step 1: List Everything You’re Protecting
Start with a simple list of every device that needs to stay powered during an outage. For a typical home office: desktop PC, monitor, router. For a POS counter: terminal, receipt printer, barcode scanner, router.
Step 2: Check the Wattage of Each Device
Every device has a power label, usually on the underside or the power adapter, showing its wattage or amperage. As a rough guide:
- Desktop PC: 150–300W depending on the components
- Monitor: 20–50W
- Router or modem: 10–20W
- POS terminal with printer: roughly 60–100W combined
- Laptop charger: 45–90W (though a laptop’s own battery already provides some outage protection)
Step 3: Add It Up and Leave Headroom
Add the wattage of everything on your list. Then choose a UPS with a Watt rating comfortably above that total — not exactly matching it. Running a UPS near its maximum capacity shortens both its runtime during an outage and the working life of its battery over time.
Step 4: Understand VA vs Watts
UPS units are labeled with two numbers: VA (volt-amps) and Watts. Watts is the number that matters for sizing — it’s the real power your equipment draws, and it’s always equal to or lower than the VA figure. Don’t size against the VA number alone; check the Watts rating specifically.
Step 5: Match to a Model
For Panpower’s range specifically: a single PC and monitor fits comfortably on the 720W MT1800; a POS counter with a terminal, printer, and router fits the 1200W MT2000; multiple devices or a small server setup needs the Online Series, which scales up to 10,000VA. See the full breakdown in our Panpower UPS buying guide.
A Quick Sizing Example
A home office with a desktop PC (250W), a monitor (30W), and a router (15W) totals 295W. A UPS rated around 600–720W gives comfortable headroom above that load — which is exactly the range the MT1800 sits in.
Frequently Asked Questions
What happens if I connect more devices than my UPS is rated for?
The UPS will either shut down immediately on battery power or trip an overload protection, cutting power to everything connected. Always size with headroom, not right at the limit.
Should I include my laptop in my UPS sizing calculation?
Laptops already have their own internal battery, so they’re less critical to include — though their charger still draws some wattage while plugged in, worth accounting for if it’s connected.
Buying Support Through CompuOne
Explore the full UPS Lebanon range at CompuOne, or read our guide on choosing the right Panpower model.
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