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Free tool
UPS & power calculator
Add up your devices' power (PC, DVR, cameras, router, modem) and find the UPS size in VA, the approximate battery runtime and the monthly energy cost.
| Device | Watts | Qty |
|---|
Typical reference values: check each device's label for accuracy. Real runtime depends on battery age and temperature and on inverter efficiency (85% assumed).
What size UPS do I need?
To choose a UPS (battery backup), add up the watts of everything you will plug in and convert them to VA using the UPS power factor (budget models are often 0.6). So 300 W needs at least 500 VA, and a 30% margin is wise. Runtime depends on the battery energy (volts × amp-hours) and the load: one 12 V 9 Ah battery keeps a router, modem and DVR with cameras running much longer than a PC.
Frequently asked questions
What is the power factor?
The ratio between real watts and VA. A 1000 VA UPS with a 0.6 power factor delivers at most 600 W.
Why does my UPS last less than calculated?
Batteries lose capacity with age and heat, and deliver less at high load. Treat it as an estimate.
Is it useful for security cameras?
Yes: keeping the DVR/NVR, cameras and router on during an outage lets you keep recording and receiving alerts.
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