My LR is kinda small @12x16 and it just takes a little while. Guess it depends on how cold the room is to start. The heater is either on or off...not adjustable, doesn't power off by itself. One night I fell asleep a couple hours with it on and it was really warm in the room. To sum it up, it's a nice unit for the price, but if heat is on the top of your list, I might look elsewhere. Hope it helps!