Thermal-Bowl is the answer to freezing water bowls.

Simply plug it in, and your pet's water will remain open all winter down to 20° below zero Fahrenheit. All electronics safely sealed inside.  5 1/2 foot, steel-wrapped cord to prevent abrasion and chewing.  96 oz. or 1.5 gallon size. Limited one-year warranty.
 

96 oz. Size (KH 2010) - $ 21.79