What Size Electric Heater do I need?

What size Electric Baseboard or Space Heater do you need?

1) Measure the length and width of the room to determine total square footage.

2) Select your level of insulation

  • Poor - Little insulation (Older homes) - 12.5 watts per foot
  • Average - R-11 in walls and R-19 in ceiling - 10 watts per square foot
  • Full - R-19 in walls and R-38 in ceiling - 7.5 watts per square foot

 

3) Make adjustments as necessary.

  • For ceilings above 8 feet - increase wattage by 25% for every additional 2 feet in height
  • Use a minimum of 1000 watts in a bathroom
  • If a recommended wattage falls between two sizes - select the large heater
  • For colder climates (prolonged winter temperatures below 20°F) use the next higher wattage up to 15 watts per square foot

 

4)  Use the chart below to calculate the recommended wattage or calculate it yourself with this example:

A room that is 10 feet wide by 13 feet wide with an 8 foot ceiling and Average insulations =  10 x 13 = 130 then 130 x 10 watts/per square foot = 1300 Watts

 

 

Room Size
(Sq Ft with 8 foot ceiling)
Watts
(Poor Insulation)
Watts
(Avg Insulation)
Watts
(Fully Insulation)
20 square feet 250 250 250
40 square feet 500 500 500
60 square feet 750 750 450
80 square feet 1000 1000 750
100 square feet 1250 1000 750
120 square feet 1500 1250 1000
140 square feet 1750 1500 1250
160 square feet 2000 1750 1250
180 square feet 2250 2000 1500
200 square feet 2500 2000 1500
220 square feet 2750 2250 1750
240 square feet 3000 2400 2000

 

Please Note: All these numbers are for general information - each install will vary depending on many other factors.