Lots of youtube videos of making actual boxes for your water troughs.
Here is most of my post from Off Course:
[I] The K & H heaters have thermostats, so they turn on & off as needed. Applause to them for that. Another HUGE savings factor on electricity, bedside using being smart enough to use a smaller wattage heater in the first place…
I cut a piece of plywood to fit over slightly more than just half of my 100 gallon Rubbermade stocks tanks. Cut a sized to fit hole in the plywood, where the heater cord WITH ITS COVER, come out of the top of the stock tank. I cut this hole so the cord will then be hidden behind the tank & unreachable to prying paws & nosey mouths. Then bolt the plywood cover onto the tank.
Not only does it help hold in heat during the winter, especially during the strong Prairie winds we get here in Oklahoma; in the summer the cover helps to shade the water from the sun, keeping it significantly cooler.
I painted my plywood black side up for winter. White side up for summer. I went the extra mile & then coated the paint with a food grade varathane or urathane I bought on Amazon. So any snow melt or rainwater that runs into the tank is not tainted from paint. I know, a little paranoid, but I love my for legged beasties.
Another thing I do for the water tank is set in the slightest depression of earth, that I filled with fresh manure. I then bank the water tank with compost for added insulation. When I do change the tank water, I try to dump so the water goes into the depression, thus preventing an ice slick around the tank. Then rebank the compost.
Quite honestly, I have never had an issue using just the 250 watt heater. The top cover makes all the difference in the world. I do own a 500 watt heater, just in case. but have never had to use it. Granted, I do not live in Buffalo NY with 8’ of snow.
Here is their zone chart: http://www.khmfg.com/edi/images/medi...Tank-Chart.pdf
They say I should be using a 500 & 750 watt heaters on my tanks, but again, putting a top cover on the tanks makes all the difference in the world! We do just great in subzero weather with the 250 watt heaters.
One can also build an entire plywood box for their tank, & insulate it if they choose. Thus making a small wattage tank heater more probable for those in the perpetually frozen Great White North. Though again, covering at least a portion of the top of the tank makes all the difference in the world. Me, as said, I just bank the tank with compost.
If one has an appropriate plug in place, they may also try using “Thermo Cube” type plug ins, to help save on electricity. I have seen them for sale in a couple of different on/off temperature ranges. http://www.amazon.com/Farm-Innovator.../dp/B0006U2HD2
Hope what I do saves others many dollars. It sure has saved me $$$.[/I]