For those of you with chickens and other animals, you might be wondering how water stays melted when hoses cannot be hooked up. I used to think that chickens needed to have water inside their coop in the winter along with their food. I bought heated bases for the traditional waterers, but the chickens made a continual mess of the waterer - with bedding and poop in the water. And you are only asking for rat and mouse problems if you keep these inside the coop!
As it turns out, chickens will wander outside in even the coldest of temperatures for food and water.
After spending tons of money on different solutions, I found low wattage stock tank heaters to be the easiest solution in 5 and 2.5 gallon buckets. Stock tank heaters are now made to go into many different plastic containers too. If you cant run a hose due to cold temps, the bucket can be small enough to take easily take inside to change water. Stock tank heaters are thermostatically controlled only to go on when the temperature gets below freezing. I prefer a bucket and stock tank heater over the heated (plug in) bucket because if one side fails, either the heating or the bucket, you still have the other to use.
I like this 250-watt version for a bucket from K and H Pet Products (available on Amazon).