We dont have electricity where our animals are. We run a long extending cord out to the water basins for the water heater. We live in upstate NY and we get really cold here. Its the only way ive found to keep their water from freezing.
True, I find a bit of clear plastic (or clear-ish tarp, or fogged window, etc) on the fence, put outside waterer up against the clear plastic, and it helps tremendously with keeping water thawed for longer