Generators are used by organisations whose machinery and IT equipment must remain online at all times during an extended power outage.
While uninterruptible power supplies are also designed to protect against such power outages, their purpose isn’t to deliver backup power indefinitely.
The primary role of a UPS system is to bridge the gap before the generator has time to start up and synchronise, or to keep equipment running long enough to enable a safe shutdown. It also cleans the power, whether from the mains or generator, to smooth out problems such as sags or surges.
Backup generators are typically found in mission-critical environments such as data centres, hospitals, call centres, and financial institutions. Most of these organisations will have large, stationary generators that are designed to handle multiple devices.
Diesel generators have built-in fuel tanks that typically last 8-12 hours, although some models are fitted with external tanks that extend running time for up to several days. An alternative would be a gas-powered generator.