Electric baseboard heaters are a very efficient alternative to forced air heating. They are a reliable supplement for wood, coal and pellet burners. Perhaps the most useful aspect of baseboard heaters is the flexibility in temperature control they provide. Each room of the house can be kept at a different temperature. The correct size baseboard heater for the room is necessary for the room to be heated efficiently.

Measure the Room

Measure the room. You will need to determine the square footage of each room. Measure two adjoining walls and multiply the two figures. This will give you the square footage of the room. To figure the square footage of a 10-foot by 12-foot room, multiply 10 times 12, which equals 120. The room has 120 square feet of floor space.

Wattage

Figure out what wattage the heater should be for the room. About 10 watts is needed per square foot of floor space, so multiply the square footage of the room by 10. For instance, a 10-foot by 15-foot room, or 150 square feet of floor space, would require a 1500 watt baseboard heater. For a room with a high ceiling (more than 8 feet high) add 25 percent to 10 watts for each 2 feet of ceiling height over 8 feet. For example, you should use 12.5 watts per square foot of floor space for a 10-foot by 15-foot room with a 10-foot high ceiling. Baseboard heaters come in a wide variety of sizes, from a 24-inch 375-watt heater to a 120-inch 2500-watt heater. Have a licensed electrician run the wiring for the heater to make sure it is up to local building codes and that there is sufficient electrical supply to run the heater.

Wall Space

Consider how much available wall space you have for the baseboard heater. A typical 1250 watt heater is 60 inches long, 8 1/2 inches high and 3 inches wide. A 500 watt heater is about 28 inches long, 6 inches high and 2 1/2 inches wide. Make sure there is enough room on the wall to have at least a few inches of space between the end of the heater and the adjoining wall. Install two 1500 watt heaters on opposite walls in a large 15-foot by 20-foot room to avoid taking up most of one wall with a baseboard heater. Install the heater under a window if possible. This is recommended but is not absolutely necessary for the heater to function efficiently. Keep in mind that the furniture in the room should not be right up against the heater. Furniture too close to an electric baseboard heater could be a fire hazard or, at the very least, could damage the furniture and interfere with proper functioning of the heater.

Source:

HouseNeeds.com: What Size Electric Baseboard or Space Heater Do You Need?

Heater-Store.com: Heater Calculator

Heater-Store.com: Baseboard Heaters