Pros: Simple and durable
Cons: Needs to be on level ground and not in the open
I've used every winter for the last five years, it's works really well with metal double wall water fonts however it's *not* meant to be used with plastic water fonts. The heating element is on the underside and it has a simple thermostat that comes on when the temps falls below 40 degree F. It generates just enough heat to keep the water from freezing. The manufacture doesn't guarantee that it works below 6 degrees F however I've used in temps colder than that and it's still going strong after five years. The only downside is that it really need to be on a level surface so the water doesn't splash out. Also you might want to place it on a hard surface like a board. This is because one year I was breaking it down in the spring and when I lifted it up a mouse ran off! He had spent the entire winter nesting under heater where it was warm. He also had a supply of feathers for his next and a steady food from dropped chicken feed. Fattest mouse I ever saw.