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ITGlossary · UPS technology
MTBF
The average operating time between failures of a device, used as a measure of its reliability.
Technical level:Intermediate
MTBF is expressed in hours and is derived statistically from the behaviour of a large number of units or from component reliability calculations. A figure of 100,000 hours does not mean that a particular unit will run for about 11 years without failure; it means that, across a large population of units, failures occur on average at that rate.
It is mainly useful for comparing reliability and for designing redundant systems. Together with MTTR, it is used to calculate a system's availability.
Only compare MTBF figures when you know how they were calculated, because different methods and conditions give very different numbers. Also, the figure for a UPS often excludes the batteries, which wear out much faster than the electronics.
Related terms
- AutonomyThe time a battery-powered system (like a UPS) can continue operating critical loads after a power failure.
- MTTR (Mean Time To Repair)The average time it takes to repair a system after a failure occurs.
- Cooling FanA built-in fan in UPS or batteries used to dissipate heat during operation.
- AC EfficiencyIndicates how efficiently a UPS converts incoming AC power into usable output power during normal operation.
- Capacity SystemParallel UPS units that share the load with no spare unit (N configuration), so the failure of one unit overloads the rest.
- DC EfficiencyMeasures how effectively a UPS converts battery power into output power during battery mode.