What is the difference between UPS and a generator for power protection?

An uninterruptible power supply, or UPS, provides immediate battery backup power when utility power fails, covering the gap of seconds to minutes until a generator starts or power returns. It also conditions power to protect against surges, sags, and electrical noise. A generator provides longer-term backup power by converting fuel into electricity, but requires 10 to 30 seconds to start and reach full capacity.