MTBF and MTTR (Mean Time Between Failures / Mean Time to Repair)

MTBF (Mean Time Between Failures) is the average operating time a piece of critical infrastructure runs before it fails. Such infrastructure includes a generator, UPS module, chiller, or switchgear breaker, while MTTR (Mean Time to Repair) is the average time needed to restore that component to service once it has failed. Facility engineering teams use both figures, sourced from manufacturer data and their own maintenance logs, to size spare-parts inventories, schedule preventive maintenance, and calculate theoretical availability: higher MTBF combined with lower MTTR raises the modeled uptime of a given system. The metrics also inform N+1 versus 2N redundancy decisions, since a component with low MTBF or high MTTR is a stronger candidate for parallel redundancy rather than a single high-reliability unit. Vendors publish MTBF ratings for UPS modules and generators in the tens of thousands of hours, but real-world MTBF is typically lower once installation, environment, and maintenance quality are factored in — a gap operators track through their own outage and repair records rather than relying on datasheet numbers alone.