Friday, June 14, 2013

A Year with Solar, or is it: “Wait until he figures out what a monumental waste of money that was”. . . . .

Less than a month after installing our two large Solar Panels on Viking Star I overhead a passerby make the above statement to his companion.  I did reply to him that he was a bit presumptive with his judgment and that modeling indicated they would have a ROI of less than 5 years.  I can tell you he just discounted me as one of those ‘fantasy’ types.  Well, here we are – a bit over 1 year on this system and I think it would be good to look back and see how well they actually worked.   Was installing Solar a great idea, or as so elegantly put a ‘monumental waste of money’?

Before deciding to place the panels aboard, one of the greatest difficulties I had was getting actual DATA from folks on how their panels performed.  I got things from ‘All We need’ to ‘Great’, to ‘Fills my batteries by 11am’.  (Monumental guy did not have any panels, so I am not considering his input).  But without exception:  all the ‘observations’ were gut feelings.  No real data.

Being a (at one time, before crossing to the dark world of Marketing) Engineer – this just would not do.  So I set out to model the panels, you can read more about that here:

To get actual data - the charge controller I purchased has data logging capabilities.   But before we get much further, let’s make sure some ground rules are established:

  • We cruise in the Pacific Northwest- if you are somewhere else, likely your results will be different.  (See the Modeling post to learn more).
  • Our  ‘Cruising’ season is March through the end of October.  During this time we are very rarely in port, and even more rarely have access to low cost shore power.  

That last point is a critical one, as it means -- almost without exception -- every AH we consume we need to make on the boat.  Either via the large 270A  Leece Neville alternator attached to our main engine, or via the Kubota Dc generator -  OR  via the Solar Panels.  And this, to be fair, is huge.  It is VERY EXPENSIVE to generate electricity on a boat.  I estimate it costs $1.14 / 100Ah running the DC Generator – direct costs only (Oil and Fuel).  That does NOT include any amortization for the original cost of the Generator, or depreciation for its replacement.  Every 100Ah costs over a buck….   And with us away from the dock so long, costs add up very quickly!

OK, on to the results.  Here is a graph of the actual daily AH log as provided from the Solar Regulator.  The thin purple line is the actual daily results – you can see cloudy days and sunny ones.  The black line is a 15 day rolling average - to try and smooth things out a little.  Finally, the thick blue line is what the modeler predicted our output would be.

1 year actual results
(Click on image for a larger version)
You can see the modeler did a rather good job of predicting.  In fact, over the year the Actuals were 2% greater than the Modeler predicted.  Looking behind the scenes in more detail:  Over our cruising season (March through the end of October) we produced an average of 124.7Ah/day.  We saved 245 hours of run-time on the generator and that results in a raw ROI of 5.5 years.   Figuring in the Federal Tax Credit, it drops to 3.9 years.

So, for a boat cruising in the rainy Pacific Northwest, the Solar Panels have a ROI of under 4 years.  And best of all?   I do not need to listen to the Generator during most of the time as a result!   In fact, we are back into the time of year where we likely will not need to use the Generator at all until the end of September.  And then only when we do Laundry.

(To see all our posts on the Solar Panels, click here: )


  1. I really have a hard time believing someone would say that. I mean are they just completely ignorant of how cruising works? Or maybe they just have a perma-dock queen boat that is always plugged into shore power? It is a mystery.

    Sundowner doesn't even have shore power. Literally everything comes from solar when we don't run the main diesel engine (no generator). I can't imagine it any other way for a boat that spends any real time at anchor or in far away places.

    1. Well, perhaps I would assume - based on what little I know of this person - his boat does not leave the dock much, and when it does does not exercise the anchor much :-)

      We use a rather largish amount of power for a cruising boat - but perhaps not for a 'power' boat - we have the small refridgerator, an Engel freezer, and we find the laptops can use a lot on their own. So in the end: we could not be happier with our panels.

  2. I'm not disciplined enough to monitor our results as thoroughly as you have done and we've had the panels for a much shorter time than you have. Despite that my WAG at a payback time was 6 years and I honestly don't remember what all went into that but it did involve the back of a napkin and some beer so it must have been very technical. We're tied up to the current bush for another couple nights and then its off to Port Angeles. We'll give you folks a call whenever we get an arrival time firmed up for P.A.

    1. Well, see - that goes to prove the Power of Beer and WAGs!!!

      We will be in Friday Harbor until the 27th, and then be heading down over the next two days towards the Seattle area.