u/Flimsy-Attention-722

Need to replace my unit. Looking at US Energy solutions and Comfort Monster. They borne have good reviews but I'm hoping to hear from someone here who had used either.

My daughter inherited a stamp collection and knows less about it than I do which is next to nothing. I told her I would see wen fast I could find out. Can we start with, I'm assuming canceled stamps have no value? Is the some general rules to this that will help me figure out how to help her? Thanks