Something I don't understand about portable heaters

[datsunfan]

I've been searching this board and reading posts about portable electric space heaters. But I still don't understand why two different units with the same heat output are rated differently as to how much area they can heat. For example these two:

http://www.northerntool.com/shop/tools/product_200632847_200632847

and

http://www.agrisupply.com/milkhouse-style-electric-heater/p/88346/


They both say 5200 btu, 1500 watts, but the more expensive one is rated at 1000 square foot and the cheaper one says 400 square foot.

If the btu's are the same, what difference does it make how the heat is delivered?

 

[Falcon67]

1500 watts to 1000 sq/ft sounds like marketing BS. Electric heat is 100% efficient so what goes in comes out. A better fan will help spread the heat around.

 

[rburke65]

Neither one is being compared to a constant such as a room with the same R value, temperature rise in a given amount of time. As said someone is BSing someone. And a watt is a watt.

 

[dfiler2]

Rating a heater by square footage makes no sense, even if all of the outside conditions are the same, a 1000 square foot greenhouse and a 1000 square foot well insulated building would have completely different heat loads.

 

[jvitez]

Rating a heater by square footage makes no sense, even if all of the outside conditions are the same, a 1000 square foot greenhouse and a 1000 square foot well insulated building would have completely different heat loads.

+100!

Btu's are btu's, and watts are watts. Well, 3.413 btu's per watt actually.....

How much heat input you need is entirely dependent on the size, insulation, air sealing, design temp (how hot you want it to be inside), outdoor temp, wind, size of man door, size of garage door, level of insulation of each, and size and thermal efficiency of windows. That's why HVAC pros need to do a detailed calculation when designing systems for houses and commercial buildings.

We can be a lot more cavalier for garage calculations, but you should completely ignore any mention of how many square feet any heater can heat. Only look at heat output and go from there.