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Old 05-10-2019, 12:35 AM   #1
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City: Pnw
Country: USA
Vessel Name: SARAH TOO
Vessel Model: 40’ beer can
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How much solar?

I’m sure it’s being discussed at length but what do people need for their solar set up’s. We are away from shore power full time on the hook but only part time on board. I’m considering a full-time AC system to run the fridge but not much else while we are away. But when we were on the boat we would want more power for pumps lights heating. I’d rather not rely on genset at all which is a tall order I know, but I want maximum sustainability, and we have a large roof area to use for collection. With new more efficient panels and mppt controllers how much do we need to keep us online full time unassisted? I can get around 1200w on the roof and match it to 400AH or so battery pretty easily.
If running inverted AC full time is not feasible I do have a 12v chest fridge we could use but that would be a whole different system. I’m even considering a 24v house bank and and running everything on AC. Might waste some power here and there this way but it would be easier to wire, and the power lost at lower voltage might be more than the losses from conversion to low volts for lights and phones etc. Basically the fridge drives the whole system lol. I would need 12v for furnace and water heater though.

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Old 05-10-2019, 04:03 AM   #2
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Join Date: Jan 2010
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I am a proponent of installing as much solar as you can physically fit on your boat .you always find use for electric. If you have excessive power you can heat hot water or run a water maker

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Old 05-10-2019, 04:31 AM   #3
City: Canaveral
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1.2 kW-hr on your roof is an excellent spread. Considering your profile of using the boat part time, but being on the hook, your panels will have plenty of time to bring your batteries up full. You can easily support double that battery capacity if you need to expand in the future. Definitely install a PSW inverter for your 240/120 VAC.

It sounds like you have not installed a refrigerator yet, or are open to changing it. Since that is your highest load, purchase an A+++ domestic unit. Also, I'd go with a domestic hot water heater (240V) as well, if you're looking to upgrade, although it would be better to buy a unit designed for solar installations so it can accept an engine loop heater.

Since you're in the PNW, on a given winter overcast day those panels should still generate about 1kW in energy, maybe a bit less. But an efficient refrigerator will use 0.5 kW per day, so you're good to go!

Since you don't have/need air conditioning, there is no need for a generator.
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Old 05-10-2019, 05:14 AM   #4
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City: Litchfield, Ct/Punta Gorda, Fl
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There are several articles in the misc section of this forum’s library that discuss sizing and installation of solar.

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Old 05-10-2019, 06:28 AM   #5
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The battery killer is always the reefer system.

There are multiple options , all work if selected for your lifestyle .

The archives will help decide what should work better for you.
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Old 05-10-2019, 06:42 AM   #6
City: Carefree, Arizona
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If you're planning on being away on boat for lengthy periods why worry about keeping a fridge going? Seems like a lot of effort for a cold beer. Where in PNW would boat be moored?
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Old 05-10-2019, 09:52 AM   #7
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City: Pnw
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Vessel Name: SARAH TOO
Vessel Model: 40’ beer can
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Well mainly the reason is just so we don’t have to shuffle fridge stuff like condiments and semi perishable food etc. plus a cold fridge is a clean fridge, decommissioning the fridge every time is a pain in the butt.
The boat currently has a dorm style fridge, not sure if it’s A+++ rated but it looks modern. I guess my thought is if the system can handle 3 days on its own then it can handle indefinitely too, so why wouldn’t we? Little more load on electric and batteries but sometimes keeping that stuff on and warm is better than a shut down period. I dunno.

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