How much current does the Eltako ER12-001 need to switch the output?
The electronics does not have an internal power supply and therefore no standby loss.
  The microcontroller is activated when the control contact closes. This switches the bistable
  relay to the correct direction. The bistable relay switches back either when the control contact
  opens or when the control voltage falls.


(page 306)

Control current universal control voltage at all control voltages 4 mA ± 20%.

Source, page 312.