“Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.” – Mark Twain

Trying to Make Sense of Solar Options


I posted about some potential solar options last year.  But after considering the feedback I received it was clear I had more homework to do.  So I have been trying my best to do good due diligence on solar panels.  But I now feel like I have hit a stage of analysis paralysis.  I am hoping someone can help get me past this hump.  Here are the options I have been evaluating.

What type of Panel?

Solbian: With Compass Marine’s help last year I had determined that for the Solbian panels I could fit two (2) of the SL90L or SP112L panels on my bimini.  They have the same foot print but the SP series is the highest efficiency and therefore more money.  I don’t see the SL series listed on Solbian’s website anymore plus I think I would pay the premium for the more efficient panel if I went this route.  So for now I am planning as if I were to use the SP series but I am looking at the SP100L to make sure I get the best fit on my bimini.  Estimated cost without including the solar control (see below) is $2,750.

Rigid Panels: This would obviously mean I would have to build a frame and would have a bigger hassel for dismantling and storage below during a storm.  I would also mean more overall weight.  Neither of these are things we want when cruising in a smaller boat.  But I think I still need to consider this as an option.  So for this setup I looked at two 140 watt Kyocera panels (KD140SX-UFBS).  Estimated cost without including the solar control is $1,800.

Chinese Semi-flexible Panels: I know, I know.  Quality sucks.  You can’t believe the ratings. They are just poor quality knockoffs of the Solbians.  But the biggest thing I want from the Solbians in the mounting and storage ability.  I could possibly be satisfied with the performance of these panels.  And now you can buy them from American companies or on Amazon that might help with warranty issues.  I can’t not include them in my evaluation without later doing the “what if” game.  So I looked at the Go Power! GP-Flex-100.  Estimated cost without including the solar control is $1,350.

Here are the specs from the panels:

Peak Power (watts) Open Circuit Voltage Rated Voltage Short Circuit Current (amps) Rated Current (amps)
Solbian SP100 102 21.8 18 6.1 5.7
Kyocera 140W 140 22.1 17.7 8.68 7.91
GP-Flex-100 100 20.8 17.8 6.10 5.62

What type of Solar Charge Control?

MPPT vs. PWM: So I was starting to put together a review of maximum power point tracing versus pulse width modulation charge controls.  I was going to my typical go-to source for info, Compass Marine AKA Maine Sail, and he just published an evaluation of the two types of charge controllers.  His conclusion is that MPPT Controllers give you approximately 20% more power than PWM.  Seems like a no brainer but let’s see what that money difference is before we decide.

For costs, I looked up a few different options.  Compass Marine has a few brands I have seen him post favorably about when it comes to controllers: Genasun GV-10 MPPT, MorningStar has been given some good words in the past, and I also wanted to look at something bigger and Compass Marine has recommended Rogue in the past.  For PWM, Compass Marine used the MorningStar PS-15, the MorningStar Sunwize Sunsaver Duo and the GoPower! Digital Solar Voltage Regulator.

Here are the specs and costs on these controllers:

Type Amps Stages Cost
Genasun GV-10 MPPT 10 4-Stage $170
MorningStar SS-15L MPPT 15 4-Stage $200
Rogue MPT-2024 MPPT 20 6-Stage $250
Rogue MPT-3048 MPPT 30 6-Stage $350
MorningStar PS-15 PWM 15 4-Stage $85
MorningStar Sunwize Sunsaver PWM 25 4-Stage $170
GoPower! PWM 30 4-Stage $124

So clearly there are differences in quality; I included some lesser quality products like the GoPower!.  But if you look at similar MorningStar products you are going to pay around twice as much for the MPPT as you would for the PWM.  But if we are talking about a 20% increase in efficiency for about $100 it seems worth it.

What do I really need?

I did a power consumption work sheet.

Power Consumption worksheet 2

Based on the work sheet I am estimating around 125 Ah per day usage while cruising in the Bahamas and the Caribbean.  My real-world data courtesy of my Victron Battery Monitor puts me closer to 80 Ah per day.  I am continuing to size based on the 125 Ah per day because I do expect to use more power when we hit Florida, the Bahamas and the Caribbean.  But the hours of good solar energy should go up too.  So I am estimating I have 5 hours of good solar for my estimated power generation.  I don’t expect to get more than 4 while we are still in the Northeast but we will also be at a dock during that time except for weekends and some limited cruising.

So, that’s a long winded way of saying if I assume 85% charging efficiency on the solar panels and I run my engine for 1.5 hours per day, I would generate 115 Ah per day.  So this would mean that I could go with the Go Power! or some other semi-flexible panels and the result would be I would have to run my engine an extra hour on 1 or 2 days during the week to keep near 100% SOC.  Additionally I wouldn’t gain much power generation for the double the cost of the Solbian panels.

So where am I thinking wrong? 

The things that are in my head are as follows:

  • Is 5 hours too high of an estimate for good sun in the tropics?
  • Is 85% of the stated Ah rating too high to use on the panels?
  • Should I be taking temperature into account and, if so, how?

Bottom Line

After thinking about these options it’s clearly the installation method for the Solbians is what got me going in that direction.  While rigid panels offer the best performance for the area, the inconvenience of installation and storage take them off the table.  As far as charge controllers go, the MPPT seem to be the best bang for the buck and worth the small amount of additional money to get better performance.

Next step: research the Chinese made semi-flex panels and MPPT controllers and place an order.  Unless someone talks me out of my plans for solar again.

6 thoughts on “Trying to Make Sense of Solar Options

  1. After much agonizing, we bought 2 Kyocera 140w and 2 Genasun GV-10. When we went to install them, we realized there was no way we could live with that did not look terrible. After many hours of trying, we sold them to a friend with a bigger boat (we are 34, he is over 40). If you go with 2 or less of the Kyocera 140W panels, I think the Genasun controllers are hard to beat.

    Now I bought a Midnight Solar “Kid” controller and 4 x Renogy 100W flexible panels. The panel are probably the same panels as the GoPower, but are only $200 each. Since they are so light, the do not need a reinforced arch and are easy to move. I can fit 400W of these panels easier than the 280W of Kyocera. The price and convenience are hard to beat. If they only last 2 years I will be bummed, but it is a risk I am willing to take. Reviews of them that I can find seem pretty good overall, but none reflect 2 years on a sailboat in the tropics.

    • Yeah, those panels are high on my list. I used the GoPower because those are available at Defender and they usually stick by the products they sell. I think the GoPower and the Renogy panels are very close to the same.

      I did a layout of the Renogy on our bimini after I posted this today. It looks like I could fit 250 watts on the bimini. I also have a plan for another 2 100 watt panels. I just need to think it through some more.

      Thanks for the post and for reading.

  2. I feel your pain buddy…been going over all the options and scenarios and it can boggle the mind. Good luck with whatever you decide.

  3. Pingback: Planning Our Solar Array « s/v Smitty

  4. Pingback: Solar Install |

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