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Wait Mike! You said that you didn’t like being constrained by a budget. That’s true, where money is concerned, but the budget I am referring to is our energy budget, or in other words, how much electricity we have to run all of our boat’s tools and toys. We’ve spent a lot of time talking about increasing the solar or wind generating ability on our boat, and even the addition of a gas-powered portable generator. Some or all of those things are still in the works, but just about everyone recommends that the first step in the electrical input-output equation is determining what your needs are. Hence, the budget!

Disclaimer: This is yet another item in the long list of things I know very little about. More trial and error.

The Budget image below is a work in progress. I spent a chunk of the morning pouring over the various manuals we have for our boat gear, trying to find the manufacturers’ estimated power consumption for each device. Some I could find and others I couldn’t.

Assuming we could find what a particular device consumes, the next step was to estimate how many hours per day we will be using said device. Some are easy to calculate (for example an anchor light is on from dusk ’til dawn, or approx. 12 hours) while others are only used intermittently or while underway. Because of this, a portion of the figures in the image are correct while others are just placeholders. So, if a device uses 1 Amp and we run it for 12 hours, that equals 12 Amp/hours.

What do we have to draw from? Our boat’s battery bank can obviously only store a certain amount of energy. We have 8 – 6V batteries, each rated at 105 AH. Wired in series/parallel (my terminology might be off there) that should equal 420 AH at 12V (I certainly am leaving room to be correctly here). This doesn’t mean that we can use all 420 AH though, as the batteries couldn’t be depleted to zero without killing them.

Now here is where this gets really similar to a financial budget, at least for us anyway. Just like money, we are really good at spending the electricity. Determining how we will replenish the supply is the yet-to-be-determined part. Let’s see what we can come up with! 🙂


  1. Mike, my theory on electrical and monetary budgeting is the same–overestimate the outgo and underestmate the income, thus arriving at a positive balence. I also do my battery bank figuring with no more than 50% of the theoretical capacity, since that’s all you can use without ruining the batteries. In fact, there are some recommendations for only using ~25-30% of total battery capacity as one’s starting figure. One also needs to allow for power loss in the runs to the device from the batteries, as well as loss from anything ( like the panel) in the line between the batteries and the device. Sort of like allowing for the money you will spend for items not in the budget!

  2. I find it useful to think of an “at anchor” energy budget and an “on passage” energy budget.

    For example, we would use our GPS/radar/AIS a lot on passage and probably not at all at anchor. Also, we would have our anchor light on while at anchor but running lights on passage (which may take more amps).

    Kudos to you. We, by the way, haven’t really done this well yet. We know from experience about what we use right now at anchor but we are installing some energy hogs like our SSB and eventually a watermaker and also adding solar.

  3. Ahh…Pirate’s at Norman. And you just haven’t lived until you stagger off the Willy T from a night of fun beverages.

    Consider swapping all your lights over to LED’s,particularly the interior lights.make sure you use the “warm white” ones,as the regular ones are too harsh. There are some good LED’s for anchor lights now too.
    Save your electricity budget for crankin’ out the bushwackers!!

  4. Very nice. I actually posted a copy of my “budget” next to the panel, so the family could see the size of the items.

    The 420AHs is when the batteries are NEW. Use the 25% factor, which over time will become 50%! Also, you want to either be conservative, have a separate starting battery, or practice pull-starting.

    All kidding aside, do practice pull-starting. Make up an emergency handle ahead of time and store it next to the engine. Lift the engine ~ 1/4 up so that it is a straight pull. Use a little starting fluid – it helps. It’s not hard and it is a good skill to know. If the batteries get flat, no big deal.

    Allow something for fans. I carry an 18-inch fan and we find it very useful as an AC substitute, particularly when buttoned up because of mosquitoes. I thought it was a silly waste of space when I found it on the boat. Truthfully, we use it far more than the AC, because we can use it on the hook and it only pulls a trickle on low. Sometimes we use it with the AC, to spread the cool. Sometimes we set it on the nav table facing up, sometimes in a bedroom door.

    We also have 4 small fans, all of which see some use.

    The fridge is the power hog. Ouch. But I don’t like my propane fridge enough to recommend it. Fortunately, I have learned to like stout served warm. My gut says you will not use the fridge all of the time. I think I would rather have warm food than be tied to a gas generator, and solar and wind may come up short.

    Otherwise, your budget seems to be close to what we have found. We can go 2 days without charging, but that is the safe limit.

    • Good reminder posting the budget by the panel.

      I wrote fans on the list but didn’t include values because we have yet to buy any. Knowing how hot we were while hiding from the mosquitoes last year we definitely need to get some!

      As for pull starting, for sure we should learn how to do that. I just ordered the Yamaha service manual this morning. Do you think that skill will be detailed in it?

      And warm beer? ummmm… I don’t think so.

  5. Pull-starting is covered in the owners manual ( on pages 11.5 to 11.6. It’s easy.

  6. We have a “magic Bullet” blender ( Not the best blender ever, but it fits in the shallow kitchen cabinets and has made many dacs and smoothies.

  7. Btw, I think your math for the fridge is wrong? Not sure, but I think the 5 AMPS you mentioned is what it’s using when it is ACTUALLY COOLING. But, with a decent fridge it is not supposed to work 24×7, more like half an hour every 1.5 hours or something like that. And only during those 30 minutes it only consumes that much? I know somebody who spent like 4 hours with a stop watch next to his fridge to actually measure how often does it turns on and how long it works, to make the budgeting for it proper.

    • I am sure you are right, Max. I was just doing an estimate / average kind of thing, based upon whatever info was in the manual. Once we get back on the boat I’ll be able to check it a bit more accurately, as your friend did. I do know that the previous owner installed a little computer muffin fan to circulate the cold air in the fridge. He told me that this helped a lot.

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