expressing uncertainty in the past: "could be" vs. "would have been"

Question

Yesterday I wrote the below snippet in an email, but looking at it again it doesn't sound right:

Last term I did way too much teaching related stuff (my fault, didn’t really know how much time consuming it could be)

Now, the sentence between parenthesis is the one bugging me. I'm not sure if something like this would have been better:

... (my fault, didn't really know how much time consuming it would have been).

So, I guess my doubt stems from the usage of “could be” vs. “would have been”, but I'm not sure how to even frame it in grammatical terms. Any thoughts on this would be very much appreciated!

Sorry if the above makes little sense, but I'm not a native speaker.

Answer 1

You're using the conditional perfect tense here, so an acceptable form of words is:

... (my fault, [I] didn't really know how time consuming it would be).

Note

You should leave out the word much. Time consuming is an adjectival phrase describing it; it is not quantifiable, and therefore much is inappropriate.

However, you could also write

... (my fault, [I] didn't really know how much time it would consume).

and it would be equally correct and convey the same meaning to the reader.