Why do people .......................?

[easygrinder]

buy an extractor fan and then get a variable speed controller to turn it down, why not just get a weaker cheaper fan in the first place

 

[DirtyCanuck]

Sound and temperature control.

 

[Prot3us1]

A smaller fan running at 100% will usually cost more to run, be louder and wear out faster than a more powerful fan that is running at a lower speed...But its a good question

 

[easygrinder]

Sound and temperature control.

if your fan is too loud but has the right temps, then its the right fan,

if your fan is too loud and you need the temps to be a bit higher, then you got the wrong fan,

so, i don't think this is a good reason

plus if you have a 100 cfm fan for arguments sake and you run it at 80% i'm not sure that it would use less electricity than an 80cfm fan