Added Oct 30 2017
I bought this one on Amazon and we love it, the kitty loves it too. It was only about $45. There are so many feral cats in our area and they keep the rat population to a minimum for us so the least we can do is provide homes for some of them. If you have a covered outdoor area with an outlet you can plug this in, takes very minimal power to run. https://www.amazon.com/gp/product/B004ZJOH06/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 here is a picture of the kitty in my backyard enjoying her house.