It took over a week for her to even try it. The unheated one I purchased last year was at one end of the area, the pad that reflects her heat in between. She would lie curled up on the pad near the doors, but would enter neither of the houses. Then one day she tried the heated one, and now she stays in it most of the time except on sunny warm days. She is 14 years old. I recommend both the heated and unheated ones.