This may sound dumb since I've raised chickens for quite a while, but what is the purpose of the waterer's with heaters. Possible from keeping the water from freezing during the winter??
Thats it. There are several ways to keep water from freezing in the winter, but not all of them are effective so pay attention to make sure your chickens have water.
We live at 8,000 ft in Colorado, sub zero, -20+ in the winters, we still check the waterer every day, and still have to crack through the top think ice layer, but without the heater to set the water on, we would be refilling and deicing a water all day!