sysop@hub:~/tools/ups-runtime-calculator$

ups-runtime-calculator

How long does the UPS hold, and is it large enough? Enter what hangs on it and what is printed on the UPS. You get the load, an estimate of the runtime with new and with aged batteries, and the values to put into the shutdown software.

what hangs on it

Anything else, or the measured total, in watts

the UPS

Rating in VA Power factor Battery blocks of 12 V in series Capacity of one block in Ah Battery condition Runtime you want, in minutes

An estimate for sealed lead-acid batteries, good to within about a third. Lead batteries deliver far less than their printed capacity when they are emptied in minutes, which the calculation takes into account, and real units differ in efficiency and cut-off voltage. The runtime chart of the vendor for your model is better, and the runtime the UPS itself reports after a self-test is best. The typical watts per device are measured draws, not the figure on the power supply label: a 500 W power supply in a PC that draws 80 W counts as 80 W. A plug-in power meter costs little and replaces the guess. Related: server hardware guide: power, small office blueprint, SNMP cheat sheet for reading the UPS, PoE budget calculator.