Much will depend on your physical location in the USA. What works for some places is useless for others. I am in MI, which has so many (normally) cloudy days, that solar power is pretty ineffective to power the fencer or a water tank heater. I would be wasting my money on such things for my location.
Further West, the sunshine is “more powerful” in the brightness that comes on the land. This is measured by Lumens. So even if I get bright days here in MI, the sunshine is not as bright, less powerful, for those solar cells than sunshine in Nebraska for instance.
We built our wood insulated boxes that hold the stock tanks, using Styrofoam insulation to help keep the water unfrozen. Sure didn’t cost $600!! Find a local Carpenter to make some up for you around your tanks. Our wood boxes have a half cover, screwed down, so only one end is open for drinking. Half cover also is keeping the tank warmer and preventing horses from reaching the sunken tank heater. We don’t use floating heaters since they seem to have a shorter life and are IRRESISTABLE to the bored, playful horse who will pull them out and break them or set things on fire!!
With the boxes being insulated, I only run the heaters at night, since our horses are all in the barn at night. This night use of heaters is on cheaper electricity, with no chance of a possible short in the heater to Zap a horse trying to drink. The water stays warm all day for us, with no heater running. So I get a bit of money savings doing this. I put a cover on the open half of tank for the night, again to help hold in heat, save some money.