Hiya, and welcome to BYC!
We heat our coop 5'x12' coop with a 400-watt oil-filled radiator heater. On nearly its lowest setting, it will keep our coop to 40F, except we have to turn it up a tish when it goes below zero. This one can get a bit too hot to touch, so we have it on a shelf behind wire so chickens can't get to it. If it would ever tip over, it's got a safety feature to shut off, or if it overheats, it will shut off. We've run this one for eight years without an issue. I have one of these under my desk too.
I'll put links in the pictures so you can see them at TSC. They could be cheaper elsewhere as I didn't shop around.

For the hutches in the temp/breeding coops, we put a 200-watt Cozy Coop radiant heater in those. It's a bit thinner and smaller than the NewAir above, and it doesn't get hot. These aren't meant to heat an area, but they are to just be there in case the birds get a chill, then they can go stand/lay by them.

Even with the NewAir keeping the coop to 40F, the 5-gallon waterer near the floor has gotten ice on it, so we have a Cozy Coop behind it.

We heat our coop 5'x12' coop with a 400-watt oil-filled radiator heater. On nearly its lowest setting, it will keep our coop to 40F, except we have to turn it up a tish when it goes below zero. This one can get a bit too hot to touch, so we have it on a shelf behind wire so chickens can't get to it. If it would ever tip over, it's got a safety feature to shut off, or if it overheats, it will shut off. We've run this one for eight years without an issue. I have one of these under my desk too.
I'll put links in the pictures so you can see them at TSC. They could be cheaper elsewhere as I didn't shop around.
For the hutches in the temp/breeding coops, we put a 200-watt Cozy Coop radiant heater in those. It's a bit thinner and smaller than the NewAir above, and it doesn't get hot. These aren't meant to heat an area, but they are to just be there in case the birds get a chill, then they can go stand/lay by them.
Even with the NewAir keeping the coop to 40F, the 5-gallon waterer near the floor has gotten ice on it, so we have a Cozy Coop behind it.