How to Size an Electric Baseboard Room Heater

Stay warm this winter

electric baseboard heater

So what do you do when you have a cold room that just won't warm up? Well, electric heat may be the fuel source of choice if natural gas or propane fuel is not viable or available. In many cases adding supplemental electric heat is the easiest "serious" way to add heat to a room because it is a stand alone solution that requires no additional ductwork or piping.

A 120 volt or 240 volt electric baseboard heater is also a great solution to add heat to a room if easier ways of adding supplemental heat to a room have not resulted in the desired results.

An electric heater can come in a 120 volt or 240 volt version. It can also come in a straight resistance heating style or a hydronic heating style. The resistance heat style just heats up a heating element in the baseboard heater. The hydronic style actually heats a self contained fluid that in turn heats a finned tube and provides radiant convection heat.

Before going through the expense of buying an electric heater, you may to try checking out these possible problems that prevent heating a cold room:

  • Heating register is closed or not adequately opened
  • Dirty furnace filter is reducing air flow
  • Heating ducts are crazy dirty with debris!
  • Hot air from furnace coming out of heating register is blocked by furniture or draperies or carpeting
  • Thermostat located in an area where it gets warm quickly
  • Thermostat is not functioning properly, or is improperly set or adjusted
  • Leaky / drafty windows or doors
  • High ceiling that require a reversible ceiling fan
  • Poor insulation in walls


Sizing an Electric Room Heater:
Once you decide the type of electric heater you want to use to heat a room, the next step is determining the size of electric heater you will need.

Electric heaters come in a range of sizes and are measured by how much energy they consume and heat they put out. This unit of measurement is called a Watt.

To size an electrical heater for a room, first understand that the size will be affected by heat loss through the walls and windows in the room. So the amount of insulation and quality and number of windows will have an affect on the heater size.

Room Heating Size Rule of Thumb:

As a rule of thumb, assume the heater to be sized at 10 watts per square foot of room being heated.

  1. Measure the length of the room and the width of the room.
  2. Multiply the length times the width and then multiply that by 10. This will give you the rough wattage for the heater.
  3. A 1500 watt / 240 volt unit can heat a 150 to 175 square foot room.
  4. If the room is poorly insulated or has a lot of windows, select a slightly larger unit.

You may also want to check out the 5 Ways to Reduce Your Home Energy Cost in your home to reduce the demand for supplemental heat.