The thing should list how many watts it uses. That would be listed per hour. SO, multiply that value by 24 and you get per day, and 30 to get per month. Now, if it has a thermostat, it might not be on all of the time. If you look at your electric bill, that would get you your cost per KW (thousand watts). You can figure out a worst case cost if it was on all of the time. It probably won't save you any money, but may make you feel more comforatable. Depends on what you do with the rest of the house, and how easy it is to close off that one room. In most places in New England, electric costs are worse than other forms of heat, but who knows this season.