Ride-Through Time

Ride-through time is the period a data center's UPS can carry the full IT load on batteries or flywheels after utility power fails. It lasts until generators take over. Typical lead-acid or lithium-ion UPS systems are sized for roughly 5 to 15 minutes at full load, while flywheel systems provide tens of seconds. Standby generators normally start and accept load within about 10 to 15 seconds, so the ride-through window exists mainly to cover generator start failures and transfer switching, giving staff time for a controlled shutdown if a generator does not start. Longer ride-through raises battery cost, floor area and fire-safety requirements, so operators balance it against redundancy level. Uptime Tier III and IV designs pair ride-through with N+1 or 2N generators to avoid ever relying on it for long.