The Best Way to Size a Space Heater

NewAir space heaters are a reliable way to heat your home. They provide power and flexibility, allowing you to concentrate heat where it’s most needed most and save a few bucks on your heating bill. If you’re looking for a space heater, how do you know what size to buy? How big does your space heater have to be to heat the room it’s put in?

Estimating Heater Size

The easiest way to figure out whether a NewAir space heater is big enough is to remember this guideline: 10 watts per square foot. For example, a 10 x 12 foot room has an area of 120 square feet, so to warm it you will need a space heater that can produce at least 1200 watts (120 * 10 = 1200). This rule of thumb works well for most rooms, but there are a few factors that can throw it off.

Ceiling Height

NewAir AH-450 Electric Oil Filled Space Heater

Rooms with high ceilings are difficult for NewAir space heaters. High ceilings not only means there’s more air to heat, but the heat will also accumulate farther above your head than normal, which either means it will take longer for the heater to warm you up or it will run continuously without ever warming you at all.

For rooms with high ceilings, the best solution is to increase the heater size an extra 25 percent for every 2 feet of extra ceiling space.


Windows are bad insulators. They’re exposed more directly to the outside air and are therefore colder than the surrounding walls. When it’s cold outside, they’ll absorb the heat from the air and radiate it out of your home. If your room has large windows or a large number of windows, you’ll need to increase the size of your space heater in order to keep it at a comfortable temperature. How much depends on the quality of your windows, but anywhere from 25-50 percent is possible.


How much insulation your home needs depends on where it’s located. Colder climates require more and warmer climates require less. Find out what your recommended degree of insulation is by clicking here. If your homes has significantly more than what’s recommended, lower the number of watts per square feet from 10 to 7.5. It has significantly less, increase them from 10 to 12.

Have any questions for us regarding NewAir space heaters? Leave them in the comments!

The Best Way to Size a Space Heater

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