So you’re looking for a new furnace and you’ve got a lot on your plate. You’re probably buried in comparisons between fuel types, AFUE vs HSPF ratings, and a dozen other considerations. So, it can be pretty tempting at times to just go with whatever furnace fits in the space you have available just to get the whole process over with. We don’t recommend that for a number of reasons, one of the most important being this: size matters. If the furnace you install in your home is too big, or too small, you’re going to be amazed at how quickly things are going to turn sour for you.