Bear Foot Farm's suggestion about a lightbulb in a box is a great way to go. I noticed someone in upstate NY thought he was too far north for that method, but I disagree. Though I just moved south, for the last 4 years I lived way up in Northern Michgan where winter seems to last a full 6 months---lots of snow, hard blizzards, and sustained freezing temps. I used a lightbulb/box over which I placed my water bowl. It never froze. I did try it with a larger bowl that DID freeze at the top.
I guess it depends on a lot of factors. I had moved my chicks into a pole barn and set up an indoor cage/run for them during the winter months. The pole barn was not insulated (just steel) but in there I had no wind chill issues to deal with.
But you do have added electricity to worry about. I'll in favor of keeping costs down. Since I already had another bulb running for light (to keep egg production up), I eventually discontinued using the heater. I found it easier just to go out twice a day with fresh water. They don't wast time drinking, so they get plenty before it freezes. Keep in mind that in the wild (before chickens were domesticated) they didn't sit around all day at a river or pond. The scavenged for food AND water. Having access to water a few times per day is just fine (sure, it's better and more convenient to always have water...but my point is that when its not practical to do so we shouldn't fret too much).
