Where we live, we rely on solar, petrol generators, and mains power, in that order. (Our mains bill is typically less than £15 monthly, and frequently less than £8.)
For times when sun isn't shining enough to generate enough solar power (fairly often, in the UK?), or when (shoreline) mains isn't available, a Honda Inverter would provide enough power for most daily needs? You could pipe the exhaust out of the boat, thus leaving the generator mounted in a specific location.
Personally, I have two, 2000 watt Honda Inverter gensets. I purchased both early last year. They are the single best financial investment I have made in a long time. They run reliably (generating clean, constant, pure sign wave voltage). They are very quiet, and they are quite economical to run. I can run one, or both synchronized together if more power is needed.
Lastly, there are YouTube videos online, offering a number of different ways to add external petrol tanks, thus allowing extended run times.