You don’t need to heat your chickens. Protection from wind and moisture is all you need to worry about. They will need food and water though, so you might work on a way to incorporate that. They make electric water bowls that don’t tip over. If it’s going to get cold here (Colorado), 15 degrees or lower, I will feed the girls a warm dinner at bedtime. This warms them up and has their bodies creating heat during digestion. I use a base of quinoa with and assortment of veggies, greens and dried bugs. If temps are below zero, I will do the same in the morning. We have had temps as low as -9 here with no issues. We had one who was missed during evening head count and spent the night outside alone at 9 degrees. She was fine, hungry and thirsty, but fine. Chickens are incredibly resilient creatures! You will see that given a clean, dry place to sleep and lots of clean water, they will thrive with very little work! Good luck