A method for saturating or re-saturating ammonia storage material (1) capable of reversibly absorbing and desorbing ammonia in one or more storage containers (2), wherein said material is partly or fully depleted of ammonia, with ammonia to a predetermined saturation degree comprises a. placing the storage container(s) (2) in direct or indirect contact with a thermostatting medium (4) at a temperature level TT≦ about 65° C.; and b. connecting the storage container(s) (2) to a source of gaseous ammonia wherein at least during a part of the method the gaseous ammonia during saturating or re-saturation of the ammonia storage material (1) is at a pressure PS≦ about PT, wherein PS is the ammonia pressure during saturating or re-saturating of the ammonia storage material (1) and PT is the equilibrium vapor pressure of liquid ammonia at the temperature level TT.