How to Calculate Baseboard Heat Needs

Baseboard heaters are a low-profile and inexpensive method of adding heat to a home. They can be purchased in a range of sizes to fit the available space, and they do not require any ductwork or expensive retrofitting. As electric heaters, baseboard units are rated in watts. A higher-wattage heater will produce more heat more quickly. The amount of wattage you need to heat a room depends on the square footage of the room, the height of the ceiling and the quality of the insulation.

Baseboard heaters are flexible additions to any home.
  1. Calculate the square footage of the room you wish to heat by multiplying the room's length by its width.

  2. Measure the height of the ceiling. For every 2 feet above 8 feet, you will need to add 25 percent to the total wattage. For example, a room with 10-foot ceilings would require 25 percent more wattage, while a room with 12-foot ceilings would need a 50 percent increase.

  3. Determine the quality of your insulation. An average home will require 10 watts per square foot. An older home or one built to less expensive specifications will require 12.5 watts per square foot. A home with above-average insulation (grade R-19 wall insulation and R-38 ceiling insulation or higher) will require 7.5 watts.

  4. Multiply the square footage of your room by the wattage per square foot determined by your insulation. For example, a 10-by-10 room with average insulation will require a 1,000 watt heater.

  5. Adjust the total based on ceiling height. For example, a 10-by-10 room with average insulation and a 10-foot ceiling would require a 25 percent increase, or 1,250 watts.

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