As recently as five years ago, selecting an alternator was simple. Most of us had 12-volt boats, with a few 24-volt. And 12-volt alternators were about 50% efficient, and a little better than that for 24 volts, but not enough to justify a change, at least not as the only reason.
But now we have a whole new generation of alternators with claimed efficiencies as high as 80%, and further, with the availability of higher-powered DC/DC chargers it’s easier than it was to install a charging system and battery bank at a higher voltage than the loads on the boat, so it’s time to take a deep look at choosing the best alternator for our particular usage profile1.