We installed one by cutting a hole for it in existing wall. This option is certainly less expensive. It includes a removable shutter for when the door needs to be sealed up. It also includes weather stripping to prevent heat/air loss. I've had it for over a year and it didn't make an impact on my power bill, which is a relief because I live in Las Vegas and the air conditioning can be steep in cost. The main thing is to train and reward your dog to accept the new door. We have 2 dogs: One older, one is only a year old. The younger dog adapted pretty quickly after a few sessions of having him come to me when called from both sides of the door. The older dog would often go outside and forget the dog door when it was time to come back in. There was definitely a learning curve, so you should make sure for the first few days that you have time to reinforce training on using the door rather than assume that a few successful uses means understanding. It takes a little longer for old dogs to learn new tricks, but I helped her by hiding her bones on the other side of the door and repeatedly calling her to come inside through the dog door. Hope this helps!