Complexity of calculating a single model versus all models of a propositional formula with a SAT solver

Question

I have little background with SAT sovers and theoretical computer science.

How can I describe the complexity of calculating all models of a propositional formula versus just the usual SAT problem of finding just one model?

I am writing a paper, in an area where finding a single of a model of a type of propositional formula is considered "easy", but for my reasearch I need to calculated all models. (I am using Picosat that can calculate all models of a logic formula.) Is there a way to describe how "hard" or "complex" finding all models is compared to finding a single model?