We are not that cold yet, and what I have done will use some electricity, but it keeps the eggs from freezing. I found a twin size electric blanket at the Goodwill, and I hung it over the back of the nest boxes, I have rear roll out nests. The blanket has a shut off after 12 hours, so I turn it on at 5am before I leave for work, and then I am home and checking for eggs by 5:30 pm. It works great and keeps the egg area darker so the hens dont try to pull the eggs back in to the nest.