I know you said you do not want electricity to them. I run the Ritchie's with the balls.  As long as the float level is set correctly and there are cattle drinking out of them I rarely have a problem.  That said, if I was installing new ones of any kind, I would definitely at least run conduit in the trench while I was installing the water lines.  Personally I would go ahead and run the wires and be done with it and just leave the breaker off.  You never know what is going to happen in the future and you would be setup for anything.  I have a big 6 hole Ritchie that has 100+ cows on it right now.  But in 30 days there most likely will only be 2 or 3 head drinking out of it.  If, we get a forecast with highs of around zero and lows of -10 for a week I will kick on a 250 watt doughnut heater in it and not have to worry at all.