I only have 3 birds, but this is my setup.
I got a small electric pet dish- it has a 25 watt heater which is thermostatically controlled, holds a quart. I wanted more capacity, so I used a 1 gallon jug, wrapped it with a 9 ft long 18 watt pipe heat tape which I already had(cost about $10, as I recall) this is also thermostatically controlled. I made a harness for the jug so it hangs in the pet dish and becomes a vacuum waterer.
it holds a lil over a gallon, and lasts me almost a week. I have not gotten a power bill so far, but dont expect much- 25w+18w=43 watt, only on when needed.
if they both ran 24x7 it would be 1032 w/day, and cost about $.12/a day for me.
Croney00-
that is a long run for that many watts. one thing you could try is to make a cord from 12-2 romex(the kind of wire that is inside your walls), using the outdoor stuff(grey) as AC current travels better in solid wire. or else you need to run 2 cords on 2 circuits, not the same plugin. and the biggest wire gauge cords you can afford.(smallest number)
solar is not gonna cut it, unless you invest thousands. even then, you are at the mercy of the sun.
another thought is to find lower wattage heaters. this will save you money, too, as long as they are enough to keep water thawed.