My general comment is, that isn't good management.
Let's ignore the fact for the time being that most chickens don't need heat.
Like most earthbound animals, chickens need hemeral lighting - a light and dark period each day. In concentration camps they used to subject prisoners to 24 hour light. Lay that one on your friend. Even a red light is too much light around the clock.
If one must heat, for instance if they have young or fragile breeds, there are better ways to do so without subjecting the animals to light at night.
Now let's get to the heat and the main reason they don't need it.
Do you know what breed/s your friend has?
Let's assume for the moment that they are what 80+ % of chicken keepers have - an American, English, Continental or Mediterranean class breed.
The first 3 come from cold climates developed in the last 300 years. New Hampshires, Jersey Giants, Plymouth Rocks, Ohio Buckeyes, Delawares, Rhode Islands, - those are very cold states in winter. Britain gets cold in the winter and Sussex, Orpingtons, Aorps are among those breeds. Continentals like Welsummers, Marans, Hamburgs, Faverolles etc. come from places where it gets cold in winter. Even Araucaunas and their derived breeds - Ameraucanas and EEs come from Chile and those American and European areas. Chile gets very cold in winter. I guarantee 200+ years ago, they didn't put white heat lamps in tight coops. Guess what, those breeds survived.
Even Mediterranean breeds can handle temps well below zero. I've had most of the Mediterranean breeds and it gets down to -20. I've never had a real health issue with them. Some of the roosters will get frostbitten combs but that's it.
Even the ancestor of modern breeds, the jungle fowl was adaptable to a wide range of climates. True, it occupied tropical areas of SE Asia, but it also lived in the Himalayan foothills. It gets cold in the Himalayans.
Ask your friend if he also heats the run and pasture. Why not? If they need heat in the coop then they shouldn't be allowed in an unheated run. What's that about?
A bird kept in a warm area at night and turned out into a -20 wind in the morning can be stressful enough to kill them. They need the opportunity to acclimate.
A warm space without big ventilation gets humid and promotes pathogens. A warm moist area combined with feces and organic matter is the breeding ground for disease.
Bacteria and viruses have a tough time living well below zero.
If the coop is able to be heated, there is likely insufficient ventilation.
There is some danger of fire when heating a coop. There are countless stories of coops burning down at night.
If one heats their coop, they better hope and pray they never have a power outage, that could kill the chickens.
Heating a coop is very expensive and negates any small financial advantage that may exist raising birds.
For that wasted money, added to the cost of housing, feed, etc. one could buy organic pastured eggs and chicken from Whole Foods Market or Trader Joe's.
Remind your friend that they go to bed wearing their winter coat, not a negligee.