The electric bill isnt too bad, ok its a lot higher than an average households at around £350-£400 a quarter (a bit less in high summer when no heating is required) but considering its a large 4 bedroom house which not only has my fishroom but 8 vivariums with bugs and snakes in as well and a 150 gallon tank in the living room its not completely over the top.
The fishroom is heated by one 2000 watt oil filled electric radiator which is set on a timer to come on at staggered one hour on-one hour off intervals during the day and 15 minutes per hour over night, and has a thermostat set at 78f so once the room is at temperature it shuts off. The fishroom is also fully insulated (thats what the foil material on the far wall and door is) and sealed so it holds its heat very well.