Subject: Is electricity ever 'used'?

I understand that in a battery, chemical changes occur, and hence the battery 
becomes depleted.  However, when you hook up, say, a coil heater to AC mains 
supply, the electrons flow through the live wire, and through the heater, and 
presumably they exit through the neutral wire.  Why can't the escaping 
electricity be re-harnessed? (If it is indeed escaping, however for the 
electrons to be 'used' I imagine chemical reactions taking place....and they 
don't, right?)  If this is wrong, then what about the electron flow is changed?  
Is it the speed of the flow?  The direction of the flow?  Or is it something 
more complex like a change in quantum state?  Or are the electrons actually 
'used' up?  Or, finally, is electricity being described as a 'flow of electrons' 
just an analogy to make it easier for high school kids like me to understand 
it's nature? (By god it wouldn't surprise me.) Thanks!

Re: Is electricity ever 'used'?