Why is a vacuum cleaner not as good heater as an electric radiator? I've read this question and answer: How efficient is an electric heater?
, but still don't understand.
If I have an electric radiator it heats the room with 1000 Watts of power. And I feel the room's getting warmer.
In contrast, if I turn on a vacuum cleaner which consumes 1000 Watts as well as the radiator, it doesn't seem to heat the room as well.
Why? Won't all kind of energy transform into heat ultimately?
 A: It is because you wouldn't hide in the corners like your kitty does!
A electric radiator is designed to be directional and therefore it doesn't heat the unnecessary part of your room. It makes you feel warming in front of it, but some part of the room don't get heated like those corner and the ceiling. In comparison, a vacuum cleaner heating the gas instead, so it is much more uniform, but less efficient from your point of view because you don't feel it (Your kitty might be happy about it though).
As what @JohnRennie, they dissipate the same amount of heat (and some become noise).
A: A more creative answer involves knowledge of statistical physics:
Using the vacuum cleaner will transfer the system (your room) in a state of less entropy (if the rising temperature is neglected) as the  dust is compressed in a smaller volume (just like the mixed state of two gases has more entropy then the state where the gases are separated). This transfer costs energy (that follows from the second law of thermodynamics) and thus the vacuum cleaner needs to use some of the energy for this transition reducing the heating power.
The heater doesn't reduce the entropy in any way.
Therefire the heater is a tiny bit more efficient.
