hello! We live in Nh, and when we built our coop, we insulated really well with a buch of stuff left over from the house. Then, we installed a light bar, that has two heat lights, one white one (250 watts) that come on in the day time, and a red 250 heat light that comes on and off just before and after the white one. We have found that with the insultion, our coop stayed a comfy 40* even recently when it was bitter windy and cold down to -17!
Some would say that the day light one is over kill, but our chickens dont come in from the rain willingly, and being cochins, they look all bedraggled and soaking wet, I have seen them come in and scratch around on the floor under the white light until they where warmed up or dry, and then either roost, or go back out! The light keeps the daytime temp even, and the shavings and coop dry! The red light gives me the ability to do a nightly headcount, and make sure everyone is present and accounted for without turning on a light. In the summer I use just a regular red bulb.
We originally installed a panel heater from shop the coop, and we love it for the peace of mind it gives us, but honestly, I dont htink it comes on very often, Maybe during the wee hours of the coldest nights, but I think the insulation and heat lights do just fine. The insulation really makes a difference on the drafts too, there are none!
Many people believe that chickens dont need any kind of heat, I just know that I was not comfortable sleeping in my warm bed unless I knew my critters were safe and sound. I do agree that they dont need or do well at higher temps, but I like to keep them above freezing. usually around 40-45.
You will get lots of advice, some of it conflicting, but the sound and consistant advice will harp on the need for ventilation, but no drafts. Dry Dry Dry. (humidity and built up ammonia can kill or at least sicken!) and adequate space for roosting, nesting, and moving around if confined on nasty weather days. Light via windows is also encouraged, but can be worked around.
You will sort out what sounds right to you, and what you can afford. My best advice is to do what you need to to sleep well at night.