It's not necessary and a waste of energy to heat a coop, but it if makes you happy by all means do it. .
(For you newbies it would help if you put your location under your avatar)
We are all about the eggs! Adding a lamp in the coop increases the Winter egg production and the girls love to spread their wings and sun bathe under the lamp on cold Winter days. We sell at least $7 in eggs per day so we don't mind supplying a few dimes of energy of that for the heated water dispensers and a brooder lamp.
