12/24/48v - how to know what is optimal for 42’ Trawler yacht?

[Mtitania]

I’m starting to design a solar power system to replace my Generator on my 42’ Trawler. What size system should I be considering?

Thanks in advance for thoughts and experiences. All of our appliances are electric - including stove/oven. It’s a 40 year old boat, if that makes a difference.

 

[Ampster]

Do you know how many Watts are needed during a time when those appliances are running?

 

[svsagres]

So, what you need to look at your loads. If most of your loads are AC, then yeah, going for a 48V system will make sense. If a lot of your loads are 12VDC (lighting, refrigeration, bow thruster, etc… ) it might make more sense to be 12VDC. If your 12V loads are relatively modest, it likely makes sense to use a DC:DC converter to go from a higher voltage bank down to 13.5V (or whatever) to supply your other house loads. On the flip side, if you have a 24V windlass and/or 24V thruster, it might make sense to design around 24V.

In all cases, you need to design around your loads. I have a much smaller boat (27’ sailboat) and all my house loads are 12V, so I built my system on 12V. It meant about 16’ total of 2/0 to feed the 2000W inverter/charger, but that was better than converting for me.

 

[Mtitania]

Thanks for your response @svsgress! It helps to understand how to think about it. I‘ve got to do the calculations on watts needed, etc. which I’ve not done. I won’t be back at my boat for another 4 mos, and trying to get some outlines and research done between now and then.

The boat has DC and AC right now. But I’m not sure whether 12 or 24DC. How do you figure that out? The stove and oven are AC and I believe the watts are between 110 watts to 550 watts … im not sure about the wattage for the windlass. I have Garmin chart plotter and Simrad auto pilot. No bow or stern thrusters… Twin Cat Diesel engines. Lights have all migrated to LEDs where possible, including new deck lights. TV (Roku) is minimal with inverter, and internet router/Wi-Fi (planning on using Starlink When at anchor). Refridgerator is DC. There’s a second one, like a dorm fridge that is AC. Adds capacity that’s nice. Previous owners added that. Also not sure what water pump pulls. It’s also DC. And the toilets (electric flush) - we have 2 heads. Horn is DC, lol. I’ve got an electric kettle (AC). Our Dinghy Davit is all manual. And we’ve got 2 laptops, iPads, and other electronics also.

I’d like to be able to selectively charge the batteries from the engines if it’s cloudy out, also from the generator if needed. Going to use Lithium batteries.