A multi-stack electrochemical hydrogen compressor system, comprising: two or more EHC stacks (121, 122), wherein each EHC stack comprises; at least one electrochemical cell; and a power supply (151, 152); a controller in communication with the power supply (151, 152) of each EHC stack (121, 122); wherein the controller is configured to independently control the power supply (151, 152) of each EHC stack (121, 122); characterized in that the system further comprises: a water distribution circuit configured to circulate water through each EHC stack (121, 122); a coolant distribution circuit configured to circulate coolant through each EHC stack (121, 122); and at least one sensor (161, 162) disposed in the coolant distribution circuit at the outlet of each stack (121, 122) and configured to generate a signal indicative of the coolant temperature at the outlet of the stack; and at least one sensor disposed in the coolant distribution circuit, configured to generate a signal indicative of the coolant temperature at the inlet of each stack (121, 122); wherein the EHC system is configured such that a coolant flow distribution through each stack (121, 122) is determined based on a temperature differential of the coolant through each stack. two or more EHC stacks (121, 122), wherein each EHC stack comprises; at least one electrochemical cell; and a power supply (151, 152); at least one electrochemical cell; and a power supply (151, 152); a controller in communication with the power supply (151, 152) of each EHC stack (121, 122); wherein the controller is configured to independently control the power supply (151, 152) of each EHC stack (121, 122); wherein the controller is configured to independently control the power supply (151, 152) of each EHC stack (121, 122); characterized in that the system further comprises: a water distribution circuit configured to circulate water through each EHC stack (121, 122); a coolant distribution circuit configured to circulate coolant through each EHC stack (121, 122); and at least one sensor (161, 162) disposed in the coolant distribution circuit at the outlet of each stack (121, 122) and configured to generate a signal indicative of the coolant temperature at the outlet of the stack; and at least one sensor disposed in the coolant distribution circuit, configured to generate a signal indicative of the coolant temperature at the inlet of each stack (121, 122); wherein the EHC system is configured such that a coolant flow distribution through each stack (121, 122) is determined based on a temperature differential of the coolant through each stack. a water distribution circuit configured to circulate water through each EHC stack (121, 122); a coolant distribution circuit configured to circulate coolant through each EHC stack (121, 122); and at least one sensor (161, 162) disposed in the coolant distribution circuit at the outlet of each stack (121, 122) and configured to generate a signal indicative of the coolant temperature at the outlet of the stack; and at least one sensor disposed in the coolant distribution circuit, configured to generate a signal indicative of the coolant temperature at the inlet of each stack (121, 122); wherein the EHC system is configured such that a coolant flow distribution through each stack (121, 122) is determined based on a temperature differential of the coolant through each stack.