It still feels like black magic that you can take heat -- however diffuse -- from an area that is already colder than the interior of your house (e.g. the air outside) and use that to increase the existing heat differential still further, transferring energy against the heat gradient! (As Flanders and Swann memorably put it: Heat won't pass from a cooler to a hotter/You can try it if you like but you far better notter :-D)