Teaching load for lecturers and professors is usually given in hours per semester (German: Semesterwochenstunden = SWS). And of course this differs from country to country and from state to state. Senior researchers with a full-time position in Zurich should teach 4 SWS; full professors at the University of Zurich should teach 6 SWS, in Baden-Württemberg (i.e., Universities of Konstanz, Heidelberg, Stuttgart) teaching load for professors is 9 SWS. A course has a certain number of hours per semester, usually this is the number of hours student spend in class; this is also given in SWS. Depending on this number, a professor in Zurich teaches two to three courses per semester, while a professor in Konstanz teaches three to four courses. That's almost twice as much!
Two of the courses I teach or taught in Konstanz, I already taught in Zurich ("Introduction to Perl for computational linguists" and "Introduction to Prolog for computational linguists"). For the Perl course, students in Zurich would earn 3 credit points, in Konstanz they get 9. In both cases, I taught 2 hours per week in class face-to-face, students then had to do exercises. There was also a tutorial, where students could go to get advice for solving tasks, this was one or two hours. I had/have a teaching assistant for this tutorial hour(s).
According to the Bologna rules as implemented in Switzerland and Germany, 1 ECTS point is equivalent to 25 to 30 hours per week; this "hour" is made of 60 minutes, whereas the hour in "SWS" is made of 45 minutes only. So for 9 ECTS points in a 15-week semester, students should invest 15 to 18 hours (for a 14-week semester, its 16 to 19 hours). If we subtract the face-to-face hours, students have to invest 12 to 15 hours per week working on their own: reading articles, solving tasks, preparing talks, etc.
For a programming course, students should get immediate feedback. Usually, I prepare several tasks per week, students then have to submit their solutions before the next lecture, the teaching assistant helps with assessing these solutions. For the face-to-face time, I have to invest a certain amount of time for preparing slides and example programs; this time is the same, irrespective of the number of ECTS points students get. But it makes a huge difference when preparing tasks, so students spend 15 more hours for 9 credit points or 3 more hours for 3 credit points, and the difference is even bigger with respect to assessing their solutions and giving feedback.
Taking the face-to-face time into account, professors in Konstanz have to invest more time for teaching (including preparing each lecture) than in Zurich, depending on the SWS for each course, it's 1.5 to 2 times more. But considering the number of credit points for each course and taking into account the time needed for preparing appropriate tasks and giving adequate and helpful feedback, it's way more: 3 courses with 2 SWS and 3 to 4 ECTS points each (ca. 6 face-to-face hours and 12 ECTS points in total) vs. 4 courses with 2 to 3 SWS and 9 ECTS points each (ca. 9 face-to-face hours and 35 ECTS points in total).
Teaching load for lecturers and professors should thus be calculated taking both numbers into account: the number of face-to-face hours (i.e., SWS) and the number of credit points students can earn. The ECTS system should not only be used for calculating the amount of work of students but, as this has a direct impact on the workload of instructors, it should also be taken into account for them.