In the past student assistants who have a dual relationship as a student and employee were regarded as employees and all printouts were charged to the organizational unit.
Starting from 01.04.2017 the student relationship is prioritized and student assistants are considered as students. They will have a free quota of CHF 18.- per semester. If a student assistant has to print for his work, you have to transfer balance with the print tool at https://print.ethz.ch
PhD students are regarded as employees and printouts are charged to the organizational unit.