Solar System design for mini houseboat questions

Hillbilly2 Registered Users, Users Awaiting Email Confirmation Posts: 1

Hello,  I am brand new to this forum and hope that members will be able to help me learn to design, select components, then install Solar panels on my, just purchased, very tiny 28” Landau Pontoon Houseboat.  As the boat must be moored, most often, to a buoy with no electrical hook up available, I want to design and install a system that will provide enough, 110v and 12v juice to power it’s old and future Solar driven equipment.  As the attached rough diagram reflects, I want to install a number of pieces of electrical power equipment, which will allow me to use the boat on weekends with its bank of house batteries charged when I arrive.  I’m looking for guidance on how to design the boat’s complete electrical system, recommendations on the best, most appropriate and size products to purchase, and instruction/hints on how to best install/adjust them into a well functioning, off grid power system. I have tried to estimate the DC and AC power requirements to allow selection of type and size/capacity of the system’s electrical components.  I don’t really need a roof Air Conditioner, but want to determine how much it will cost to have that capacity.   I saw that Amazon is offering a 1,600W flexible panel kit for  $190 which got me thinking about using an air conditioner off-grid.  I have also included both an DC/LPG and a small inline A/C hot water heater because I haven’t decided which way to go on that

Please look at the design of my Solar system and tell me what I should change due to my mistakes/lack of understanding of Solar power, and fill in its blanks on component capacities, wire size requirements, and your recommended component brands.  Any other advice/guidance you can provide will really be appreciated as I know almost nothing about employing Solar panels.

Feel free to call me, Jim Price (Hillbilly2) at (859) 351-3215 or email me at if you need to connect with me.  Thanks for taking the time to look my design over.  Jim

NOTE:  I was not able to attach the Solar System design drawing through NAZ,  Please email me and I will froward the design drawing by email.  Really disappointed in NAZ's shortfall on being able to send out photos/drawing to the forum.  


  • BB.
    BB. Super Moderators, Administrators Posts: 33,442 admin
    Welcome to the Forum Jim...

    You should be able to take a photo (or scan), and use the little black box with sun+mountain:

    I usually use my phone, or at least use the phone to take photo and upload to post--Then I can finish the post on a laptop computer.

    My first suggestion is "DON'T PURCHASE" any hardware right now... Do (usually multiple) paper/back of the envelope designs first--Then pick the hardware that will fit your needs (and your wallet).

    For example--The Amazon 2x800 Watt flexible panels... I do not believe the numbers... The physical size of those panels are (rough guess) closer to 140 Watt panels, not 800 Watt (by physical panel size). Also, I would highly suggest avoiding flexible solar panels as they usually do not last more than a few years. Pricing is usually closer to $0.50 to $1.00 per Watt for "good" glass panels. Pricing can be all over the place--And many good panel deals are "killed by shipping costs"--And some companies have what seems to be free shipping. Anyways...

    I like to start at the beginning... And that is to design and measure/estimate your loads. Solar power is not cheap (batteries+panels are a major cost). And it is usually less expensive to choose your loads with conservation in mind. Aka smaller/efficient loads (LED lighting, efficient fan, LED TV, battery/DC powered radio/sound system, etc. And another "power sink" are "smallish" loads that run per day vs big loads (such as a microwave) that only runs 15 minutes per day.

    Just for the heck of it (and to save a lot of vague typing)... I will just make up a "plan" to show you how it works... Say this is a 28 foot (28" inch?) x 5 foot boat. And that you can fit 17.34 Watts of solar panels per square foot of roof space (very rough numbers:
    • 28 foot * 5 foot roof * 17.34 Watts per sq foot = 2427.6 Watt array on boat roof
    Again--Just making an example of the process.

    Next, figure out how much energy such an array can create per day, based on your location (again, guessing). Flat to roof array (zero tilt) near George Kentucky. Plugging into a solar calculator (I simplify the data entry numbers for "close enough" estimates and less confusion):

    48% losses are assuming Flooded Cell Lead Acid batteries, and a DC to 120 VAC inverter (more or less "worst case assumptions"--Note I am not using the "LOSSES" or 1 kWatt array size number on this website).

    The above is Hours of Sun per day... I will pick "9 months of usage" or February at 2.85 Hours of sun per day "break even" (some days more, some days less).
    • 2.85 hours of sun per day * 2,427.6 Watt array * 0.52 off grid solar AC system eff = 3,598 Watt*hours per day for "average" February day
    That is quite a bit of solar power--Enough to run an off grid cabin or very energy efficient off grid home (LED lighting, full size refrigerator water pump, LED TV, clothes washer (a few loads a week, etc.)... Obviously, as you go into summer months, more solar energy is available.

    There are various meters you can use to measure your electrical loads (like a "Kill-a-Watt" brand meter) to figure out what your loads would be.

    Sizing the battery bank... For an off grid cabin or home, would be suggesting 2 days of storage * 50% max planned discharge (for longer battery life)--For a weekend boat, your could pick a smaller battery bank (use a backup genset for battery charging, or don't go boating on cloudy days, etc.)--Use your "fudge factors" that make sense for you.
    • 3,598 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge * 1/48 volt battery bank = 353 AH @ 48 volt battery bank
    This is not a small battery bank (especially for a boat). And if you pick 24 volts, it would be 2*353AH=706 AH @ 24 volts, etc...

    I will stop here... I am sure you have lots of questions, I have made many guesses that need to be corrected... But this gives you a quick method to size your components and figure out component size/weight/costs and you can plug in the numbers that make sense for you.

    Again, solar power is expensive and does not really "generate" that much power (per $$$, per LBS, per Sq Ft, etc.)... And you will have real limitations for a boat (roof area, wind gusts, weight, space, costs, etc.). But this gives you some basic math to at least size your solar possibilities, and how much power is available....

    The load size calcs are pretty easy too. Some simple examples:

    10 * 8 Watt LED lamps * 5 hours per night = 400 Watt*Hours per evening
    1,200 Watt Microwave * 1/4 Hours (15 minute per day) = 300 WH per day

    A full size fridge:

    150 kWH per year fridge (from EPA yellow tag) / 365 days per year = 0.411 kW per day = 411 WH per day

    Take care,
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset