If you haven't yet, do it! For five years, Farmboy and I have been hauling water from the house to the barn. During winter, the trek is made several times a day to keep the water thawed. This year, December 2016, I invested in some heated buckets. I purchased mine from Tractor Supply but they are available a lot of places.
I wanted to know more about how they work so I called the company, Miller Manufacturing Company, and asked a couple of questions. The thermostatic control turns the heater on if the water gets below 42 degrees F and turns off when the water reaches 60 degrees F. They will keep water ice-free down to -20 degrees F. They use .9583 amps.
I wound up needing an extension cord for mine. The buckets are LOCKNDRY compatible (a type of extension cord) if your extension cord will be used outside. Since my buckets are inside the sheep barn, I bought a 16/3 wire outdoor extension cord (the same gauge wire as the LOCKNDRY cords). Be sure and purchase the shortest extension cord you need for safety. During the Christmas season is a good time to purchase cords because folks are needing them for outside lighting and decorations. It seemed like there was more options for shorter cords than what there normally is. I only needed an 8 and 10 foot cord.
I use a double-sided hook to attach the handle to the pen fencing so they don't get tipped over.
I don't know how I lived without these!
Note: Folks have commented one must make sure the buckets do not get totally empty. They will still keep heating and the possibility of a fire is there. And, I wanted to point out again, do use something to attach the handle to a fence or some kind of support to keep them from being knocked over and having all the water spill out.