How fast will my UPS respond to a power outage or blackout?

The transfer time from mains to battery power differs for different UPS topologies. In case of Off-line UPS, the transfer time is typically less than 10 milliseconds, in case of line-interactive UPS, this is typically less than 4 milliseconds and in case of Online UPS, it is zero. Thus the switchover time for all UPS topologies are quick enough (one cycle in a 50Hz environment is 20 milliseconds) so that computer workstations will mostly never notices the lapse.