Many of you know that I'm an advocate of simplicity and elegance in systems design. What, though, does that really mean?
Firstly, it emphatically does not mean leaving out systems that the client wants and can afford. If you're moving aboard a yacht but you can't give up your business activities, I will have no qualms about specifying a hefty battery bank, a nice inverter or two, a fair-sized solar array, shore power charger and associated monitoring instruments so that you can power some computers, a printer, long-range WiFi booster, LTE modem, network hubs, gadget chargers and all the other trappings of a modern shipboard office. If you tell me you're heading for the tropics and like your beer cold and your movies big, I'm not going to skimp on refrigeration, inverter or data storage capacity for the sake of "simplicity".
Simplicity also doesn't mean that I'm going to cut corners by leaving out monitoring shunts, specifying lower quality wiring, using non-marine breakers, or recommending other cost-cutting strategies. That doesn't pay off in the long term; the cost of replacing stuff that breaks prematurely is far greater than the cost of doing it right in the first place.
So what does "simplicity" mean around here?
Proven technology. Anything mission-critical should be based on robust, proven components. New technology, such as computerized distributed power nodes or networked multi-source AC generation, need to be proven over time in "early adopter" applications until the bugs are worked out.
Field repairable. Any competent technician, anywhere, should be able to fix a fault with common tools and common technical knowledge. Anything that requires a vendor-specific diagnostic tool should be viewed with caution.
Isolation of independent systems. A failure in one system should not take out unrelated systems. If a battery charger fails, you should be able to isolate it for repairs without shutting down the solar array or the house electrics. The engine should still be able to start if the main DC bus is dead. A failure of the power monitoring system had better not shut down the nav computer- or the head.
Logical architecture. The layout of the electrical, mechanical and plumbing systems should be clean, logical and organized so that the captain can look at the drawing, look at the equipment, and quickly understand each component's role in the overall design. This is as much a function of documentation as of the actual systems design. It is possible to have two identical boats, one "horrifically complex" and one "fairly simple to understand", differing only in the accuracy and clarity of the systems schematics, manuals and on-board labelling.
All necessary parts, no unnecessary ones. If you rely on a main diesel engine, then redundant, parallel plumbed water-separating first stage fuel filters and ultrafine second stage filters are not excess complexity, they're a necessary hedge against crappy fuel. On the opposite hand, if your routine AC loads can be run from one or a few stand-alone inverters when underway or at anchor, there's no need to distribute AC shorepower throughout the boat; it only needs to go to the battery charger.
Expandability. Many boats start out simple and end up as a rat's nest of wiring after a few additions to the equipment inventory. A good initial systems design includes the extra power distribution capacity and the conduit runs to allow clean, easy upgrades later on.
Avoid active solutions where passive ones are appropriate. Does your boat really need an air conditioner (and therefore a generator, and AC distribution, and ductwork, and condenser plumbing, and...) or could you solve the problem with awnings, better ventilation, less clothing, and some cabin fans? I'll design in the AC if you really do need it, but think carefully about the other options before dropping that money.
I doubt that any ten skippers will ever agree on what level of systems complexity is appropriate for a particular mission. I do believe that most skippers, at least among the ocean-going, long-term cruising crowd, would prefer a design that allows them (or local technicians) to fix anything that could break, without flying in a field service guy from halfway around the world. That's what I like to strive for: a balance that provides the feature and functionality you want, with a level of complexity that you can handle, and that will remain robust and reliable for many years. That balance will be different for each yacht; if you're in the market, it's worth thinking about where in the spectrum your own needs fall.