This type of pet door is usually used for cats, but I have seen many applications where it has wokred very well for small dogs.  There are a surprising number of houses that actually have ground level windows, or windows low enough that a spry little mutt can jump up into it.

As you can tell from the picture, this unit fits intto the window, much like the doggy door patio panels.  You open the window where it’s going to live, put it in place, and close the window on it.  And there it lives.  Panels are usually adjustable over a certain width, somewhere between 2-5 inches, so you do have to measure your window to make sure it will fit the width and the heigth!

For enegery purposes, look for double paned glass or at least a “Low E” glass with a coating on each side to reduce heat transfer.  The type and quality of the actual door will vary quite a bit as well.  The high quality ones will last much longer and be much more energy efficient.

The price range that I’ve seen for these pet doors is anywhere from $350 plus to less than $100.  Obviously, you’re going to see a difference in the quality of materials (fit, form, and finish) in the lower priced ones, but that doens’t mean they aren’t well-suited for the job!  There’s no need to go spend a small fortune on a doggy door if you don’t need to.  Find something that will suit your needs and go from there.