I have one of each. The reason for the alternator is that my 13 amp generator did not provide enough juice. The sum of the lectrical devices should be less than 75% of the XX amp output of the generator. In my case it was a 13 amp generator. On an appraoch at night, I have the GPS, the transponder, the radio, the nav lights,the collision avoidance thingy and the strobes running, as well as instrument lights. When I flip on the landing lights my GPS goes dead. Now, on one plane I have a 25 amp generator. On the other a 60 amp alternator. With the alternator, although it never puts out 60 amps, there is still power for everything. Alan Fairclough N87333 N94694
