How long can equipment on a UPS keep running after the power goes?
That depends on how big a UPS do you have and what kind of equipment it protects. For most typical computer workstations, one might have a UPS that was rated to keep the machine alive through a 15 minute power loss. If it is important for a machine to survive hours without power, one should probably look at a more robust power backup solution that includes a generator and other components. Even if a UPS powers a very small load, it must still operate its DC (battery) to AC converter (the inverter), which costs power. A rough extrapolation from APC’s documentation, leads me to guess that its 2000 VA UPS can operate its own inverter (with no extra load) for just over 8 hours. A 1250 VA UPS could run its converter for about 5. These are very rough guesses based on information provided by one vendor for one vendor.
That depends on how big a UPS do you have and what kind of equipment it protects. For most typical computer workstations, one might have a UPS that was rated to keep the machine alive through a 15 minute power loss. If it is important for a machine to survive hours without power, one should probably look at a more robust power backup solution that includes a generator and other components. Even if a UPS powers a very small load, it must still operate its DC (battery) to AC converter (the inverter), which costs power.