Of all the winter watering I've done, I always needed electrical heat to keep it from freezing.
The nipple waterers are great -they do well to keep messes from happening, but I've always had to put one of those aquarium heaters dangling inside the bucket. It needs to be checked frequently for issues such as going dry or leaking, Even then, the nipple device itself sometimes freezes up at -20 and -30. This winter wasn't terrible, and I don't think we saw that this year, but it's Maine so any temperature is possible :)
I have a metal base heater too, I try to have a couple of back-ups on water, especially in the winter, In the warmer months I just put out rubber hose dishes full of water- but I have like 45 birds who drink water like crazy.