How long do UPS batteries last, and how often should they be replaced?

Design life and service life are different numbers and the gap is mostly temperature. A EUROBAT Long Life class VRLA is classified at 10–12 years on float at 20 °C; in a plant room running at 30 °C that becomes roughly five years, and at 40 °C roughly 2.5. Australian field policy for comparison: AusNet uses 12 years typical while capacity stays above 80%; Powerlink uses 12 years for 2 V cells and 8 years for 12 V monoblocs. For a monobloc UPS string in an uncontrolled room, planning on 4–6 years is more realistic than planning on the design life.