What are good methods for determining course instruction workload equivalency? The courses at my university are assigned a number "units" that basically correspond with the number of in-class hours per week, i.e. a 4 unit course is often two 110 minute sessions per week. Different types of courses require different amounts of time for the instructors. Professor teaching distributions are often set by simply stating something like "a regular faculty member must teach 1 four unit course per quarter". The courses in my department vary from 10 students to 300, we may get teaching assistants, and courses are traditional lecture styles, laboratories, project based, etc. It is likely not a good idea to say that 1 four unit course with 10 students requires equivalent time/resources as a 4 unit course with 300 students, but that is what we do. Instructors may not get fair teaching distributions due to this and it also has bearing on merit and promotion cases.

How do other institutions and departments compare courses in terms of instructor workload? I assume there may be ways other than simply the # of hours in class per week (credit/unit measure).

Edit: I'm particularly interested in precise definitions of this measure.
Actually, most universities I've heard about specify either courses or numbers of “contact hours” per week. It is the job of the department chair (or executive officer or equivalent) to make sure everything is properly distributed within the department, so that one faculty member isn’t teaching only 300-student lectures while another faculty is only teaching specialized seminars for 10 students.