1st volts = potential difference - or - potential work that can be done.
2nd Amps = the flow of charge per second through a simple circuit.
3rd watts = The work being done - or - power it takes for the work to be done.

ok now lets look at this. If you incress the volts the amps will decress for the same of power. Same goes for amps. If you incress the amps you will decress the voltage to get the same amps. step-up/down only incress or decress the Voltage or amps not the power. What you get out of a gene/dynamo (as far as watts go) is all you get. So if you have a 12v 2amp gene/dynamo all you can get from is 24 watts. Now if you step up the voltage to 48 volts than all you'll get 24 watts but now at .5 amps. There is no way to incress the watts at all. Thats why the electric company bills you in watts. Because there no way to cheat.