Moderator Post (s) for this thread: >Very strangebyHandyman on 12/10/2008
Assuming the quality of insulation of the room is satisfactory and considering the cost of resistance heating, the rule of thumb I use is 10 watts per square foot of room area. Therefore, if your room is approximately 150 square feet, the minimum rating of the baseboard heater should be 1500 watts. Look on the back of the baseboard heater or inside it for any labels indicating how much power it uses. Try to match the heater with one closest to the power the present one uses to avoid underheating the room on one extreme or overloading the electric circuit at the other extreme. Do not install a heater which consumes more power than the existing unit unless you are certain the existing electric wiring will carry the additional current or you get an electrician to heavy up the circuit.
I have seen the 6 foot heaters with 220 volt 1500 watt and 8 foot heaters with 2250 watts on the shelf at Home Depot. Unfortunately, the ones from Home Depot come only in white color which means you have to repaint them to match paneling or another color. I have seen both the Cadet brand and the Fahrenheit brand made by Marley at Home Depot. Personally, I like the Fahrenheit brand since it looks a little more rugged but haven't bought anything yet while trying to find some baseboard heaters off the shelf in a factory brown color. (I don't want to try spray painting white baseboard heaters brown myself using high temperature paint if I can avoid it!)
BTW, some money spent on insulation both in the attic and walls is money well spent if you are using electric heat. You will find that running several KW of electric baseboard heat will make you good friends with the power company.