Cumulative observing efficiency (as a percentage of the elapsed survey time) as a function of time for each eROSITA camera (labeled according to the associated Telescope Module, TM) during eRASS1. With the exception of TM5, badly affected by light leak, all cameras achieved an efficiency of more than 95% by the end of eRASS1, with TM1 reaching close to 99%. The largest loss of net observing time was caused by an ITC malfunction on February 10, 2020.