@Mfranks, I was in the same boat. I have chicken wire over the roof of the run, then tarps over that. The plug end of a cord will fit through the opening of the chicken wire. So I have a heated dog bowl kind of waterer with the cord going straight up to the roof of the run, and the plug sticking through. The extension cord is on top of the chicken wire, but under the tarp, so it stays out of the weather.
The tarp is held down with bungee cords hooked through the grommet holes of the tarp, then hooked on the fencing of the run. I unhook the tarp at the corner, fold it back, plug or unplug as needed, then resecure the tarp.
We've used what @aart described to take care of the hole we cut in the garage wall that we strung the extension cord through, as there is no exterior outlet.
The tarp is held down with bungee cords hooked through the grommet holes of the tarp, then hooked on the fencing of the run. I unhook the tarp at the corner, fold it back, plug or unplug as needed, then resecure the tarp.
We've used what @aart described to take care of the hole we cut in the garage wall that we strung the extension cord through, as there is no exterior outlet.