Most of the time when buying a house you know your square footage(sq ft). If you don't know the size of your home, we can always look it up for you. Otherwise, knowing the width, depth, and height of the area you are heating is important. We do not want to oversize a heater for the home. We also do not want to undersize the heat. Either one of those extremes will cause discomfort in the home and create a negative feeling toward your purchase. (We don't want that!)
If you share the sq ft of the entire home we automatically acknowledge that you aren't heating your entire home. (Sorry closets!) We do want to look for units that SAY they can heat that area, so it can compensate for when the doors are open. Wood stoves are the only ones you can undersize a LITTLE, only because then you can push your unit to burn the most efficiently. You want to be as accurate as possible for Pellet, so it can get started - run accordingly- then shut down (without needing to start back up immediately). Gas/LP units can heat up and cool down as needed, with a thermostat you will never be uncomfortable in your home.