Tier IV

The top Uptime classification meaning fault tolerant: the facility survives any single failure with no impact.

Current numbers

99.982% / 99.995%legacy Tier III / Tier IV availability (~1.6 hr vs ~26 min/yr down) — figures Uptime no longer endorsesas of 2025 · register ↗

~25–40% facilitycapital premium for Tier IV (fault-tolerant) over Tier III (concurrently maintainable)as of 2024-05 · register ↗

~25–40% facilityTier IV capital premium over Tier III for the fault-tolerance step (the two-independent-path guarantee)as of 2024-05 · register ↗