Imagine a professor who is reasonably conscientious about teaching: not someone who devotes themselves entirely to teaching but also not someone who just phones it in and might as well be standing in front of the class reading the textbook aloud. This is a person who is going to spend time organizing the course, preparing each lecture, being accessible for help outside the class time, and providing timely feedback to students.
Imagine that this professor is you or someone you know fairly well. Place the items, currently listed in no particular order below, into an order from TAKES THE MOST TIME (top of list) to TAKES THE LEAST TIME (bottom of list) for teaching, considering time for all teaching-related activities within and beyond the classroom. With apologies to colleagues who teach classes + labs, this list is mostly geared towards a university setting in which faculty are unlikely to teach labs but are more likely to teach giga-classes with hundreds of students. Feel free to add course formats that are missing but relevant to you:
- graduate seminar in your field of expertise
- graduate seminar in a field you want to learn about (so you teach a class on it)
- graduate or senior-level course (lecture format)
- small freshman seminar type course
- large intro non-majors survey-style course
- medium-sized course for majors in your field of expertise (TA teaches lab)
- medium-sized course for majors, topic not in your field of expertise (TA teaches lab)
And then let's throw team-teaching into the mix. It might seem that team-teaching reduces the time required to teach a course, and this is generally true. However, I recently team-taught a new course, and the newness of it dominated the team-taughtness of it. Teaching the course took an order of magnitude more time than a similar sized, non-team-taught course I'd taught before. Other team-teaching time factors are the work habits and sanity level of your teaching colleagues. Team-taught classes are a mixed bag (for faculty and students).
I have found that the emotional energy required to teach some classes is also an important factor. Perhaps the prep time for a large intro course is about the same as for a smaller course for majors, but the emotional energy necessary to teach an intro class, including dealing with a large number of students with complex lives, is definitely a factor in the overall equation of the "effort" required to teach a class. And as we all know, effort and time are very different things.