Greenhouse heater for playhouse.

I want to get one of those greenhouse tubular heater thingies for my bun Sam and his future wifes new playhouse.Its insulated and size is 5.5foot x 3.5foot x about 4.5foot high.Im wondering what wattage to get?
I know its not necessary to heat an insulated playhouse but its the first time ive had rabbits outside in the winter and for my peace of mind I just want to take the chill off inside the house.Theres a leccy supply(socket right at the top out of reach).

Could I ask if anyone has used these and what their set ups are/were?

You might be better off getting one of the green house haters like the Dimplex Coldwatcher Electric Heater from screw fix. As there is less chance of the rabbit burning it’s self, as the tubular heaters get very hot. And should be mounted out of the rabbits reach. Or have a fire guard placed round the tubular heater, to prevent direct contact with the heater.

I had them in my playhouse and they do help to keep it from freezing in there in the cold nights and help to stop the water freezing over. They were located halfway up the wall, well out of reach of the bunnies.
I have now upgraded to a "dog chalet" and panel heaters.

Thankyou both for your replies:thumb:

Just not sure what wattage/length to get.Dont want it too warm in there of course but I do want it to be afew degrees warmer than outside during very cold weather.