I don't use a heated unit like that, but I use a metal heated base with a metal waterer on top. My original one circa 1993 would keep water ice free down to at least 0F sometimes below. The one I replaced it with is seemingly the same, but in between the waterer walls & on top it now freezes when it gets below 10 for more than one day. I have to bring it in & run it under hot water to open it. I don't think many of these things do the job.