It's really important to sit down and work out a power budget, and be scrupulous. There are small systems that are running and are easy to forget about, like a sniffer, a propane shut off solenoid, radio, and so forth. To be realistic you should list everything and to be safe double it, and you'll probably be closer to real consumption. And you likely are aware that these alternative power sources very rarely achieve anything close to their rated output. That's why it's important to have the best charging system you can afford.
And while redundancy is a very good idea, remember that reliability tends to suffer the more complex the system is.
I understand this, and thank you for the reminder. I adhere to the "triple/thirds" rule: triple the amp capacity you expect to use, based on only one-third maximum performance of one's gear.
The complexity thing may be an issue in terms of failure, but I'm hoping that buying quality...and quality spares...plus the ability to test and fix the larger sorts of circuits (wires, switches, solder jobs, etc.) will serve.
Due to a relative immunity to weight kept low, I'm able to have more battery capacity aboard than most, and this is the key to my evil plans: constant charging in one form or another to keep the whole battery system above 80%.
Note that while I've stated I don't care to run the alternator to charge the batteries, if I have to, I'll have to, and then I'll have to consider a built-in genset, or more solar/wind charging capacity. But we don't anticipate running A/C or electrical pressure/hot water or vast freezers or other big draws offshore. If this changes, I would have to rethink it. Right now, it looks as if even under marginal conditions, I will make more amps than I can use. Put me in high latitudes in winter, and this might change, but we plan on being for the most part between 40 N and 40 S.