As it says on the tin 😉. I do appreciate people's mileage might vary. My university and especially department is fantastically opaque with these things, I was teaching 8-10 hours per week for 20 hours per year as a research fellow (so yeah.. I was supposed to be focusing on research), and, not knowing any better, I didn't complain. Eventually my teaching load stabilized at something like 6-7 hours per week (120-140h per year) and I assumed that was the norm for everyone in my department. Now as HoD I am discovering that some people teach like 4-5 hours per week and consider it excessive (many of our courses have very complicated timetables, with different types of sessions, not of which run every week, and course convenors sometimes ask PhDs to teach some sessions behind my back - so it's historically been very difficult to ascertain how much everyone teaches, I'm only getting to the bottom of it now).
A colleague in another department tells me that even within the same parameters (A&H, on a R&T contract), 10-12 hours of teaching per week is the norm at some RG unis...