Home   |   The Boat   |   First Mate   |   Admiral   |   Guestbook 

Date: 11 April 2016. Solar Makes Power (Part II)


My friend says people prefer to have all the information on one page and in one article. I do not particularly care to click through either. In any event, I have covered a lot of material herein. In bite-sized pieces the articles are:

  1. Batteries Store Power (Part I)

  2. Solar Makes Power (Part II) ←this one

  3. Power Used Aboard Seaweed (Part III)

  4. Inverters Make AC Power (Part IV)

The complete version with all the information
contained in the four articles is on this page:

Solar, Batteries and an Inverter, the complete series.


This is Part II, entitled
Solar Makes Power.
I now have a bunch of solar panels and could not be happier. Recently I added two more 85 watt panels. They were a gift from Bucky. With the addition of those two it matters not if I am at anchor or at a dock. Everything works. Except me!

Behind the solar panel there is an anhinga sitting on a piling to the immediate left of my wind generator.

I now have a total of 445 watts in five panels atop Seaweed. At this latitude with a plain old solar controller I have about 150 amps of power incoming each day. Life is wonderful afloat.


How to figure out how many amps from each solar panel.


Here is a rough way to figure out how much power your solar panel will produce: It is all related to the angle of the sun, closeness to the equator, and cloud cover. This is what I have found:

At the Florida/Georgia border (latitude 30) using a standard solar controller (not the more expensive MPPT controllers that are lots better) the math works out thus: Take your wattage and divide by three. Call it amps.

Panel Watts Total Daily Amps   Panel Watts Total Daily Amps
10W 3A   100W 33A
30W 10A   150W 50A
60W 20A   225W 75A
90W 30A   300W 100A
    Me 450W 150A

It matters not if I am plugged into a shore power or at anchor. My life is the same.

EXCEPT I cannot run the wall-banger air-conditioner while at anchor. Well, actually I can run the a/c unit though I must simultaneously run the engine. It has to be mighty hot and muggy for that to happen!

One thing to remember is it is not just power generation you need to deal with. You also must have a place to store the power derived from solar, wind, etc. So as you are thinking about what you require, also factor in batteries.

Aboard Seaweed I have 700+ amp hours in seven batts. I get about 150 amps per day from my solar panels. Additionally I have a wind generator that helps bump things up too when the wind blows.

Note: It is never windy enough if you are like me and anchor close to shore and in the lee of islands. I prefer calm quiet anchorages to bumpy exposed places.


Please Note: This is a multi-part series about power for your boat's goodies. It encompasses solar power, batteries and inverters. Part Three, is next: Power Used Aboard Seaweed. The complete version with all the information contained in the four articles is on this page:

Solar, Batteries and an Inverter, the complete series.

Currently (April 2016) my Comments are broken. Fortunately folks have emailed input, so here you go:

From Cap'n Todd:
1. MPPT controllers - These controllers are great IF you have multiple solar panels wired in series. If you only have one panel or have your panel wired in parallel there is very little benefit to an MPPT controller versus the much cheaper PWM or simple on/off controllers.

2. Actually during the summer we have more hours of sunlight up north than you do down south. For example right now you have about 13 hours of sunlight a day while here in Maine we have about 14 hours. In late June we will have almost two hours more sunlight each day than you do. The difference is in the sun angle (ours is lower). That matters for horizontal fixed panels, but in late June/early July we will not be far behind you in power from our solar panels due to our longer days. If you have solar panels that are angled to account for sun angle (doesn't work on the hook), you can do better here than down south during the summer. However, that requires an active sun tracking system which takes power to run and will reduce useable output and will break down now and then. It is an option for the dock queen type boat, but not needed if there is shore power available.

UPDATE: Thank you Cap'n Todd. I did correct the chart. Great explanation too!

How many solar panels do you have aboard your boat?
Do you use an MPPT controller or the standard one?

Regarding the Comments Section, found at the end of every article:

  • Before you type in each block be sure to hit the backspace key. Coding inserts a space in every box. Your email address will come back as malformed unless you remove that space. (You don't have to include your email address.)

  • The capcha is case sensitive.


2016, 2021, 2023

Categories: Boats, Gear, Wild Things,

Batteries Store Power ~ Previous Post ...    ... Next Post ~ Power Used Aboard Seaweed

First Mate's Gallery now open ~ Crew photos welcome via Email.


The Archive holds a running list with synopsis of published articles, and links to same.

A favorite aphorism:  A comet's tail always points away from the sun.

Contributions to my Cruising Kitty via
are always appreciated.

Every gift helps.

The Cruising Kitty is what boaters refer to as spending money. There's never enough aboard Seaweed!

I am also an Amazon Affiliate.

My Buddy, and his girlfriend...

Copyright Janice Marois  |  Home  |  Archive  |  Topics  |  Boat List  |  Site Map  |  Email Me  |