Related tools
Need the PoE load first? Calculate PoE power budget or size a PoE switch.
How UPS Runtime Is Estimated
Nominal battery Wh is estimated as V × Ah × battery count, then usable capacity and inverter efficiency are applied before dividing by load watts.
Why Real UPS Runtime Can Be Lower
Battery age, chemistry, discharge rate, cutoff voltage, temperature, internal UPS consumption, and load profile can change actual runtime.
Watts vs VA
UPS VA rating and watt rating are not interchangeable. This calculator uses watts for load and output comparison.
Battery Capacity in Ah vs Wh
Wh is approximately V × Ah for energy planning when using the rated battery voltage and amp-hour capacity.
UPS Runtime for CCTV Systems
Common loads include the NVR, PoE switch, router, cameras powered through the switch, and any monitor connected to the UPS.
Battery Age and Runtime
Aged batteries may provide less usable energy than their nominal rating.
Example UPS Runtime Calculation
A 150 W load with two 12 V 9 Ah batteries gives 216 Wh nominal, 146.88 Wh usable AC with 80% usable capacity and 85% efficiency, or about 59 minutes.
FAQ
How do I calculate UPS runtime?
Estimate usable AC Wh, then divide by equipment load watts.
How long will a 12V 9Ah battery run CCTV?
It depends on load, usable capacity, efficiency, and battery condition.
How long can a UPS run an NVR?
Use the NVR's actual watt load plus any connected network equipment.
Does a PoE switch increase UPS load?
Yes, if the PoE switch is powered by the UPS, its own load and powered devices contribute.
Is VA the same as watts?
No. Check the manufacturer's watt capacity instead of assuming 1 VA = 1 W.
Why is actual UPS runtime lower than calculated?
Battery condition, discharge rate, temperature, cutoff behavior, and UPS design can reduce runtime.
Does battery age reduce UPS runtime?
Yes, battery aging commonly reduces usable capacity.
Can I use this calculator for lithium batteries?
The simple Wh model can be a rough estimate, but lithium usable capacity, BMS behavior, and discharge characteristics differ. Prefer manufacturer data.