Why does it take so much less electrical energy to rotate a fan than it does to produce heat?

Question

I have this 2kW electric heater at home that's well.....2kW. I found out that I'll never need to use it again, though. My gas furnace looks like a wood burning stove that just heats up a pipe that goes up to the roof. It takes forever to heat the house so I usually run a 2kW electric heater at the same time.

Anyway, recently got the idea to set up a fan to blow air on that pipe and now the room heats up 4 to 5 times faster. I guess I was losing a ton of heat just straight up and out through the roof. I looked at the fan label this morning and it was only 60 watts!!! The blade is like 2 feet in diameter and it's pretty powerful so it got me wondering. It seems like I'm getting something for nothing here.

So why is rotational energy draw so much less power?

Sorry. Why DOES rotational energy use less?

Answer 1

That's a good question. Electric heat, incidentally, is 100% efficient - that's not true with any other heat source for your home. Unfortunately, electric heat is also the most expensive simply because it takes lots of watts (current x voltage) to produce the necessary heat and we pay for electricity by the kilowatt hour.
A fan, on the other hand, doesn't effectively heat or cool the air (the residual heat produced in the motor is insignificant in actually heating the air.) And there really isn't a heavy load on the motor (60 watts is actually a serious fan and it will move a substantial amount of air - as you have found out.)
You haven't gained something for nothing - you have simply recovered a substantial amount of heat that was being waisted - in other words, you have made your gas furnace much more efficient in doing what it was intended to do - heat your home.

Answer 2

>>getting something for nothing? No, but you are now putting energy to use that was being lost up the the exhaust pipe.

The fan isn't doing the heating, it's helping the heat in the exhaust to stay in the room.