-10F as our lows for the last few days... today we finally got snow and it warmed up to 14F...
Still no heat in the layer coop, and the 15 chukars are doing just fine, too. I did break down and add a heatlamp to my Ameraucana babies in the breeder coop, as they were showing signs of distress. They're only 9-10 weeks old, and though they're fully feathered, they're not quite used to 12°F, which is what it was IN the coop when it was -10F outside.
I have 100watt heat lamp that comes on at 7:30am during the day and shuts of at 8:00pm at night. Our temps right now is going below -7 C. I have an led night light for them that comes on after the lamp goes off so they can go to bed.
We still don't have a coop, so we have 12 chickens in a 10' x 20' chain link run, 6' high, under a Costco tent. The plastic sides of the tent are down on the 2 long sides and one short side. The other short side is pretty much protected by trees. The door is not covered. There is deep litter on the ground, some logs on the ground for roosting, and a branch tucked into the chain link for additional roosting.
Temps here rarely go below freezing for more than a few hours, but we are it the middle of a cold snap that has kept us below freezing for days. The water bucket froze solid, but the chickens are cheerful & laying eggs (although I think I learned chickenspeak for "cold").
BTW, we fixed the frozen water problem with an aquarium heater. Works like a charm.
Edited to add: The aquarium heater must be the submersible type. With an auto-shutoff in case the water level goes too low.
I have two coops and both has electric outlets and lights, both also insulated, but I don't heat niether one of them just to be completely honest, in the seconed coop where the little pullets live I put a heat lamp on sometimes when it get real cold, but when they get old enough no more heatlamp.