You would not be asking the question, if you had made a list of
electrical equipment, both 12v and 230v. You should do that before doing anything else.
Typical 230v
equipment on board a largish cruising
boat:
television
chargers for phones and laptops
microwave
air conditioning
tea kettle
washing machine/dryer
watermaker
hot water
heater
electrical heaters
Obviously, a
generator will run any of these. Besides that, a generator has the extremely useful function of
charging your
batteries.
Some of these things can be practically run off an
inverter:
TV
chargers
microwave
kettle
power tools
Those are things which are either small loads, or large loads run for short periods of time. Things which are large loads run for extended periods of time:
air conditioning, watermaker, washer/dryer, hot water
heater, electrical heaters -- are not practical or possible to run from an inverter.
For large loads run for brief periods: kettle, microwave, power tools -- you want a large built-in inverter.
If you don't want the ability to run things like that, then you can get away with a small, perhaps not built in inverter, for the chargers and the TV.
It all depends on what equipment you will use, in what way.
Even though our boat has a generator, I find the
electric kettle and microwave to be so extremely useful on board (among other things, they reduce the hazardous and somewhat awkward use of propane), that I am planning to install a large built-in inverter sometime this year.
KISS principle or not, I wouldn't want to be without the generator. There are different circumstances, where you want 230v power on board, beyond what an inverter can provide. Air conditioning is far less useful, if you can only run it on
shore power. And you save your main
engine from the potentially damaging job of
charging your
batteries at
anchor. Besides that, you have a backup redundant way to charge your batteries, should something happen to the main
alternator, which is a frightening thought since all of our navigational equipment,
autopilot, nav lights, etc., depend on having power.
That's why a typical large cruiser, designed for autonomous use away from
marinas, will have a generator
and a large, built-in inverter.
But if you really want to be without those complications, then, of course you can live without 230v power on board, or even 12v power. If you really wanted to go whole hog, you can buy oil-fired
navigation lamps,
oil lamps to light your
cabin, and you can steer by hand and use a hand-held battery-powered
GPS. Only you can decide what items of electrical equipment you need or want.