This year we decided to bite the bullet and replace our Onan. Not because of intrinsic reliability issues, but because of a lack of spare parts availability from Onan. We had several major routine maintenance issues coming up, and it was clear that parts just were not going to be available.
We looked at deck mounted, "walk-on" solar panels, but at a cost of about $10 a watt (!) the cost was very unattractive for a solution that still wasn't sufficient to meet all our needs.
You can find a detailed description of our logic and design process here:https://fetchinketch.net/boat-projects/power-to-the-people/
The short form answer: We analyzed how we use our boat, and our electrical needs, and came up with what has seems to be a very good solution for us. A DC generator from Whisper-Power. It is smaller, lighter, and much more efficient than the Onan (Light enough that the permanent list to port is GONE!). It is the last piece of a long, steady modernization of our boat's electrical system.
With the addition of this generator, and a Victron Cerbo GX monitoring system, we finally see our systems set for comfortable, simple, extended off dock cruising for the foreseeable future.
Maybe the next time we need batteries (in 8 to 10 years), we will jump to a Li system, but for now we are staying with our Firefly Batteries that seem to give us 90% of the benefit for 50% of the cost.
Fort Lauderdale, FL, USA.