This is what I use. It is in a ceramic dish.

"It features a built-in 200 watts, 120 volts AC, fully grounded built-in thermostat that conserves energy. It also has a stainless steel guard and auto shut off for safety. Full 4 year warranty."

I've had it for 2 years. It worked great last winter, keeping water from freezing below 0ú for 10 days straight. No complaints. I have also seen similar heaters for less $ at feed stores. Perhaps you might check there first.

A link that might be useful

WBU Bird Bath Heater (1517)
http://shop.wbu.com/p/wbu-bird-bath-heater?pp=12

I'm no expert in electrical matters, but I think that your 250 watt heater is probably sized for fairly large troughs, maybe livestock water pans.

That said, it should cycle on and off only enough to heat up whatever volume of water you give it. If the volume is small, like a small birdbath, it would only be drawing power for a short time. It might heat up the water a little faster than a lower watt heater but I doubt that it would waste electricity since the amount of electricity used would depend on the volume of water, not the wattage.

Claire

This post was edited by claire on Wed, Dec 3, 14 at 10:51

Thanks dreamgarden and claire!