Setting Up Electrical Systems on a Boat


Last Updated on September 8, 2019 by Amy

Electricity.  It’s something we use every day, but it’s always been one of those mysteries of the world to me.  Volts, watts, hertz/frequency and many other terms all seem like they’re from a foreign language.  Sure, I took physics in high school and can barely remember diagramming out various circuits and doing some calculations, but that was about the extent of my knowledge.  Until recently…

One of our biggest challenges on Starry Horizons is preparing the boat to be a world traveler.  On past travels, being prepared meant buying a few adaptors so you could still plug in your phone and laptop.  But things are never that simple on boats.  Not by a longshot.  Here, as briefly and clearly as I can put it, is the challenge we face.

Electricity throughout the world is generally set up using two different power systems, a 110v(volt)/60hz (hertz) system which is common in North America/parts of South America and what is used in the United States, and a 220v/50hz system which is fairly common throughout the rest of the world.

Map of World by Voltage and Frequency
Map of World by Voltage and Frequency

Fountaine Pajot offers to set up the boat using either system, and since we are based in the US and plan to return to the US once our travels are over, we elected for the 110v/60hz option.  The trouble comes in figuring out what do do when we are in countries that are shaded blue in the above map.

Our onboard generator will be sufficient to provide power for air conditioning and other AC (alternating current) systems whenever we are at anchor.  However, when we are staying in a marina, we don’t want to run the generator all the time and be “those people” who annoy everyone else around them, in addition to putting a ton of hours on the generator. Staying in a 110v/60hz marina won’t be a problem as we can just plug directly into shore power, however setting the boat up to be able to operate on shore power when we’re in a marina that has a 220v/50hz power system is the real challenge.

The Air Conditioning Dilemma

Almost everything on the boat can be run off DC (direct current, ie the batteries) power or has a small enough power draw that we can easily use an inverter.  

Except for the air conditioning units. We will likely be installing air conditioners from the factory, which are set up to run on 60hz and do not like running at 50hz.  (A fantastic discussion of what happens when you run a motor on a different frequency than intended can be found here)

In my research and in talking with our dealer, I understand that previous boats addressed this issue by buying “dual cycle” air con units that could operate on both 50hz and 60hz and then would use an isolation transformer to “step down” the voltage from 220v to 110v and thus would allow the air conditioners to work.  However, apparently the marine air conditioning manufacturers no longer offer these types of units.

So, as I understand it, these are our current options.

  • Go without air conditioning in a 220v/50hz marina.
    • This can really depend on the scenario. Some marinas we’ve been to are breezy and comfortable without air conditioning. Others, like One15 Marina in Singapore, for example, are well protected and we received almost no wind.
  • Run the generator at the dock in a 220v/50hz marina and be “those people”
    • While I’ve been told the installation of the exhaust of the generator is done in such a way to keep the generator very quiet, I still don’t really like the thought of continually running the generator 24/7 when in a marina.
  • Install an isolation transformer that can “step down” to 110v and run the 60hz air conditioners on 50hz.
    • My understanding is this would cause the motor in the air con to run 20% slower, but would also increase the V/f ratio which would likely shorten the lifespan of the air con or could kill it outright. A few people have told me some manufacturers allow reducing the voltage to the air con when using 50hz in order to keep the ratio constant/similar, but I haven’t had a chance to confirm this with a manufacturer
  • Combine a battery charger that can accept both cycles with a large inverter to power some/all of the air cons on board.
    • Our dealer has advised that the reaction time between the inverter and battery charger wouldn’t be quick enough as the battery charge would constantly be lagging behind the inverter.
  • Install a “shore power converter” that would convert both voltage and cycles. I’ve also seen these referred to as frequency converters or voltage conditioners. They would convert 240v 50hz to 110v 60hz.
    • This is a very expensive option, and getting one large enough for our needs would be quite heavy and take up a lot of room on the boat.

Installation of Shore Power Converter

This was the biggest and most complicated project by far that we tackled when we arrived in Florida. I haven’t heard of another sailboat in our size range that has this equipment on board, so there is a very good chance that Starry Horizons may be among a small handful in the world, and likely is the only Helia in the world, that has this equipment installed.

The complicated explanation (stop reading now all you technophobes!) is that the shore power converter will take the shore power input (AC power), convert it to DC power and then re-convert it back into AC power at the 240v, 60hz power that is used onboard Starry Horizons. So even though the input power may be at 230v and 50hz, the power we’ll be able to use onboard will be nice clean American style power.

We decided to install the unit because we will eventually be staying in marinas around the world where the input shore power will be different than the power that is used aboard Starry Horizons and being able to easily operate all equipment onboard (air conditioners especially!) will be very nice. Plus, we didn’t want to be those people who have to run their generator at the dock to keep their batteries topped up!

A few more technical details… the entire converter is made up of 3 components: 1) The control unit 2) the transformer and 3) the inverter. The transformer is extremely heavy (it was quite entertaining watching the 4 guys moving it onto and around the boat!) and the only place we could find room for everything was under the master berth. There is a fiberglass lining that FP made for storage under the bed that had to be cut out so that the control unit and inverter could be mounted to bulkheads. A special platform was glassed into the floor of the compartment so the transformer could be bolted down and special supports were made to help prevent it from coming loose while the boat is underway.

Needless to say, this was an extremely complicated install and probably the main reason for our extended stay in Miami.

Sandy Drilling More Holes in the Boat
Sandy Drilling More Holes in the Boat
Lifting Shore Power Converter Onboard
Lifting Shore Power Converter Onboard
Shore Power Converter Installed
Shore Power Converter Installed

So Plugging in is Easy, Right?

No, no it’s not. While we’ve been cruising many places that are 220-240V/50 Hz, it’s not as simple as plug-and-play.

First, just because these countries are on the same voltage and frequency does not mean that that are using the same plugs. We now carry two shore power plugs with us; one American-style plug and one Australian-style plug. Sometimes we’ve had to buy new plugs and cannibalize them to make a franken-plug that works for us. Other times, we’ve rented an adapter.

The 240v 50hz to 110v 60hz converter is HEAVY. We easily added 500 lbs to the stern of our boat.

And, it lets off a lot of heat. If we are plugged into shore power, we have to be running an airconditioning unit, otherwise, the 240v 50hz to 110v 60hz converter will overheat.

Would We Recommend a Shore Power Converter?

No. In fact, we’d like to get rid of ours. Does anyone want one?


  1. Hi Guys, thanks for the great blog with loads of valuable insights!
    I know this is an old blog post but can you advise what decision you came to regarding ‘shore power converters’? We may be in a similar situation travelling with a 110v boat in rest of world and would love to understand more about how to be best prepared!
    Thanks again

    1. We do have a shore power converter on the boat, and while it has been useful I don’t think I’d do it again. My biggest concern was having our air cons work when in a country with 50hz power. Our dealer swore that our air cons wouldn’t work at 50hz, but it turns out they even have a sticker on them that just say “derated at 50hz”. Derated I can live with. An even better solution is some of the new 12v air cons.

      Instead of the shore power converter, I’d do an isolation transformer to convert any 230v power supply to 110v. It would still remain at 50hz, but our inverter/charger doesn’t care about that and will still charge the batteries. Almost all the rest of the electronics on our boat run off of the inverter anyways. The one thing I haven’t done much research on is if our Victron Multiplus Inverter/charger combo would still provide 110v/60hz power (converting it from 12v battery power) or if a separate inverter or charger would be necessary for these occasions. If you go that route, definitely let us know!



  2. I think ultimately today with the advancements in lithium batteries, solar, high output chargers, and inverters, it is time to think about getting rid of conventional shore power, and running everything off of onboard inverters. You can plug just the battery chargers in, which accept any volts, or hertz you may encounter, and you get rid of the green wire shore power connection and potential safety and corrosion issues. This would certainly work for mid size cruisers and could probably be scaled to work for even large ones.

    1. Technology is moving very quickly. I doubt we will still have Starry Horizons when it’s time to replace the batteries again (7 years, hopefully??) but I expect by then things will have changed a lot.

      1. I certainly wouldn’t suggest it on your boat with the equipment you already have. But if I were building a new boat today It would probably not have a generator or conventional shore power. It would all be done with solar, large alternators, AC chargers, and water power.

  3. Hey Guys, I know I’m digging up a pretty old post here but I’m curious to know what you ended up doing to solve this problem.
    I have been racking my brain trying to figure out what makes the most sense. I’ve been thinking lately that I might just wire a separate 240/50hz AC distribution to a few plugs only, branching it off the input side of a isolation transformer to run a portable AC unit and vent it. This would allow for a PAL TV etc when staying in a Marina over the winter. Fair winds!

    1. We did end up going with the shore power converter that takes 240v/50hz power and converts it to 110v/60hz. But I wouldn’t do it again. It’s expensive, heavy, we so rarely go into marinas and even when we do, we don’t always hook up to shore power.

      A lot of the equipment on the boat would likely run fine at 50hz, including TVs, laptops ad most modern electronics. And as it turns out, even our CruisAir (Dometic) air conditioners are labeled that they’re “derated” at 50hz, but they will still run. Off the top of my head, I’d think a microwave would be most sensitive to the voltage change.

      If I were doing this all over again for our cruising agenda, I’d go for the step down transformer to bring the voltage down to 110v and just live with being plugged in to 50hz power. It’d be a lot simpler, and cheaper, to buy a new microwave (or portable AC unit if you really want) if you’re staying in a marina all winter. Now, if you’re planning on returning to the same location winter after winter, then I’d say you’d probably be better off going for a 240v/50hz boat.

  4. Thanks for sharing that link Price. I finally got a chance to read through the whole thing and I think it is a pretty good summary of the options available. However, it doesn’t discuss “shore power converters” which is what we’re looking at, and it doesn’t explicitly mention that Isolation Transformers won’t take a 50hz input and change it to a 60hz output. That issue seems to be the biggest one as the air con units in the Helia aren’t rated to run at 50hz and thus, as he discusses, will likely result in a shorter lifespan if run on 50hz.

    We’ll probably end up with a shore power converter that will be sized smaller than would be required to run the full boat, as we’d be happy to be able to run a couple of air cons and charge the batteries while we’re at the dock. This should work for us since we don’t plan on spending a large amount of time in a marina, but we do want some comfort while we’re there.

  5. Here is a link to an interesting discussion on this topic.


    One thing that caught my eye was the following:
    “Cruisers are accustomed to developing DC energy budgets, as this is where we begin when determining the size of our DC house bank(s) and, subsequently, the capacity of our DC charging systems. But we tend not to be so diligent about AC demands, usually finding enough AC power at our homeport dock to meet our needs. This is less true in Europe where the typical maximum AC power from a single dock power stand outlet will be 16 amps @ 230V.” It seems to me that this may place a practical limit on the useable output of your transformer, regardless of it’s theoretical capacity. The implication being that you will have to be selective about what you plan to run. This will obviously have an impact on the size of transformer you will actually need. Just a thought. P.

  6. we will be facing the same issue and i have be pondering this myself. I will be very interested to hear what you decide to do. your description of a shore power converter says it is “big” and “expensive”. do you have an idea of how big it is and what it costs? Thanks, Price.

    1. Hi Price. What my dealer and I are currently looking at as a solution is to get a 5Kva shore power converter, which would be large enough to run some air cons on the boat, but likely not all at once. This would be a decent compromise for us as we don’t intend on spending a lot of time in a marina if we can avoid it.

      Those units are approximately $9k+, with install probably another $1.5-2k. Not quite sure on actual dimensions, but they can weigh upwards of 250 lbs.

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