Both emergency generators and uninterrupted power supplies (UPS) are designed to back up a system when the original power source fails; however, there is a major distinction between the two.

1. Generators

Generators installed at private corporations and public facilities can generate power for long periods of time and supply power to the facility. The only caveat is that it takes about one minute from the time of the outage to the time power is supplied. Also, unlike grid power supplied by the utility, the quality of power from generators is unreliable, characterized by unstable voltage and frequencies.

Emergency generators are suitable for long-term power outages, but they are not appropriate for handling the types of power outages like dips and interruptions nor the consumer-end disturbances.

2. UPS 

The energy storage device (i.e. the battery) in a UPS ensures that clean, high-quality power is supplied. For this reason, UPS is an ideal countermeasure for a variety of power disturbances including dips, interruptions, and frequency variations.