• Electric baseboard heat is sometimes the practical solution for a room.Heizung aufgedreht image by Tribalstar from Fotolia.com
  
  Supplemental baseboard heat is used in rooms that do not have ducts connected to the main furnace, in rooms that aren't used often, or in rooms that need extra heat. Square-footage guidelines for baseboard heaters depend on the quality of insulation and the strength of the heater. There are several steps to calculating the size of a baseboard heating system.
  
  

Heat Load

• To properly size a baseboard heater, complete a heat load calculation. The Air Conditioning Contractors of America have a complete calculation in their Manual J, and HVAC specialists often refer to heat load as a manual J calculation. A homeowner can also do a rough room specific calculation. Take the area of the wall surfaces and the thickness of the wall, and estimate how quickly heat or cold moves through the walls. If there is no insulation and the heat moves through quickly, the homeowner will need more output from a heater.
  
  

Length of Heater

• A rule of thumb is that a room will need five to eight watts of electric baseboard heat per square foot of a room being heated. An average baseboard heater provides about 250 watt of electric heat for every foot of heater. So a 3-foot baseboard heater gives off about 750 watts of heat. That should heat approximately 150 square feet. If heat loss is high, however, the demand rises. A room that loses 4,000 watts per hour from heat loss will need two 8-foot heaters.
  
  

Amps and Volts

• A baseboard heater should pull 240 volts. Although it's possible to find 120-volt heaters, they are much less efficient and are expensive to run because they draw twice as much current for the same output. The baseboard heaters draw about one amp per foot, so it's important to use wire that can safely handle the number of amps drawn by the system.
  
  

Thermostat

• Some homeowners like the convenience of a single wall thermostat. This allows all the baseboard heaters in a room to be turned off and on at once. Individual thermostats on the units allow zone heating, where heaters can be turned off or on as needed. If a home has baseboard heating in a number of rooms, it's advisable to have separate thermostats for each room or section of a home.