Definition - What does Hold-up Time mean?
Hold-up time refers to the total amount of time a power supply unit (PSU) of a computer continues to operate in case of a power failure.
It is the time until which the PSU can provide a consistent voltage necessary to keep a computer powered up.
Techopedia explains Hold-up Time
Hold-up time is primarily the ability of a PSU in time, to hold and deliver electric current after power breakage, outage or shutdown. Typically, the hold-up time is measured in milliseconds.
Most modern computers PSU have a hold-up time of 15-25 milliseconds. This means the computer will continue to operate for 15-25 milliseconds after is power input is ceased or terminated. Although, the hold-up time is generally meaningless for users, 10-15 milliseconds of hold-up time is enough for the OS and firmware to store essential data and state.