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Using European AC Power Aboard

© Copyright 2005:  Jack Tyler

Taking European AC Power onboard will be an essential capability for all but the simplest boats and crews out cruising today.  Assuming your boat isn’t already set up to accept European power and you want AC power aboard, we’ll look at several basic options from which you can choose.  And depending on how simple or complex your choice, you are likely to find it easier to modify your AC system before departing your homeport, or it might make more sense to await your arrival in Europe before your AC modifications.  But to start at the beginning, you may be wondering why you can’t just change some connectors and use what’s on the dock when you arrive in Europe.

Can I plug in?  Boats from countries where 120V (and also 220V/240V) 60 Hz AC power is the norm, including North American boats from the U.S., Canada and much of the Caribbean, will show up in Europe wondering if they can just split out Europe’s 230-250V 50 Hz AC and plug in.  Depending on your location in Europe, you will find the dock’s voltage ranging from 230V to 240V and, in some parts of the Eastern Med, up to 250V.  The EU standard is 230V 50 Hz and I’ll use that standardized voltage reference when talking about European AC.  But, as you will learn with much else about the EU and its legislation, the actual electrical standards in use are to some extent still in transition.

Regrettably, Europe’s standard is single phase AC that is not directly compatible with the North American standard.  Europe’s AC is also 50 Hz, which we will discuss in a moment.  If this topic has not been considered before their ocean crossing, owners of even the simplest boats will initially find themselves on arrival in Europe wondering how they can, at a minimum, hook up the battery charger to support their 12V/24V DC systems.  This issue will surface not only because they will not want to run the engine to charge their batteries when they can avoid it, but also because they will quickly discover the cost of European diesel fuel.  Over time, they may want to add a local (which is to say, a 230V 50 Hz AC) TV, or perhaps a tool or a small appliance that they find in a local shop.  If they plan on wintering somewhere in Europe, they may soon wish to plug in a space heater…and so it goes.  Even on the simple boats, it is hard to escape the lure and luxury of AC power.

About that 50 Hz Issue:  None of the common methods found on cruising boats to accept European AC will resolve the problem of powering 60 Hz motors on European 50 Hz power.  All the options other than expensive, complex ones intended for larger vessels will result in 50 Hz AC being brought aboard your boat.  Some AC motors and other devices are intended for use on both 50 and 60 Hz.  One example is the later model inverters/battery chargers.  Another example are laptop computers, which typically come with an AC adapter that will work across the 50-60 Hz range.  Ferro-resonant battery chargers are an example of equipment that will not accept 50 Hz.  If you have one of these, it would be best to replace it before your departure.

I recommend you check the owner’s manuals and data plates on all the motor-driven AC appliances on your boat, from hair dryers to air conditioning system(s) to your AC reefer, if you have one.  (Resistance-type appliances such as your water heater will not be harmed by 50 Hz power).  What happens if you run a system designed for 60 Hz electricity on Europe’s 50 Hz AC?  Motors designed for 60 Hz AC will still work but will run approximately 18% slower on 50 Hz AC, therefore perform less efficiently, run hotter as a result, and ultimately be taxed harder and wear out sooner.   This puts us in the position of weighing the length of time over which we may use a given piece of equipment (and the amount of abuse it will receive) against the expense of modifying or replacing the system, so it can operate longer-term on 50 Hz power without damage.

For example, let’s assume you plan to heat using your reverse cycle air conditioning system, quite a pleasant and practical option in much of Europe presuming sufficient dockside power.  You will want to confirm your system is compatible with 50 Hz power and would do this by viewing the data plates on all three of the unit’s motors - the circ water pump motor, compressor motor, and fan motor.  Why?  Because it will be a critical system for your winter comfort and it will also be in constant use for an extended period of time, perhaps even for multiple winters.  Contrast this with bringing along one or two small, inexpensive 1500W space heaters not designed for 50 Hz AC but which are readily, inexpensively available back home.  These represent a small investment, will work for some time before failing, and can easily be replaced with local units found in Europe, assuming you can supply 230V AC aboard your boat (which I will later cover).  Losing the use of a small, replaceable space heater is one thing; losing your reverse cycle A/C system is something else, entirely.

Choices:  Let’s look at some escalating choices in accommodating European AC, along with their consequences and costs.  Keep in mind this is a broad topic given the diversity and in some cases, complexity of our boats - and it could be added, the desires of their crews - so treat this as a starting point in your own planning.  Also keep in mind that we are discussing ways to bring AC power from the dock power stand aboard your vessel and connecting it to your boat’s existing DC or 120V AC system.  We’ll tackle the topic of powering 230V European appliances like a TV, which you can’t plug into your boat’s 120V system, further on.


Option 1:  Minimalist Approach to Using 230V AC

Suitable for:  Crews with boats containing no high-draw onboard AC systems; who can rely on their boat’s 12V or 24V DC system (with support from a battery charger) to meet most of their needs; perhaps also for boats planning only a short stay in European waters; and finally, for boats with onboard heating capability that is not dependent on AC power, should they be planning to winter over.

Description: This option is simple, indeed.  On arrival in Europe, purchase a suitable 12V or 24V battery charger intended for marine use and designed to be used on the local power grid from a shop in your first foreign port.  If not already so equipped, also purchase a lengthy (25M+) extension cord with a Euro-standard dock power plug to which you can connect your new battery charger.  The extension cord will allow you to connect to the dock power stand but with the battery charger mounted below deck, near your house bank. Connect the charger to your house bank in a fashion acceptable to your engine’s alternator charging system.  Horta (one common first port for European-bound boats) has an amazingly large number of appliance and electrical supply stores and a 30A 12/24V charger runs barely more than €100.

 Disadvantages & Consequences:  There are not many for the simply equipped boat, although this option begs the question of how to enjoy AC power aboard beyond charging the boat’s house bank.  Let’s assume that you would like to have a small 230V AC TV aboard for news, language improvement or entertainment.  Since a North American NTSC TV will not function properly in Europe’s three broadcast environments, a smaller DC-powered inverter will need to be purchased to power a European 230V AC TV (unless it is equipped for 12V DC power).  If it’s a higher-demand 230V AC space heater that you wish to purchase and bring aboard, you will find it necessary to revisit the whole issue of AC power…so read on.

A caution:  It’s difficult to discuss anything complex or potentially destructive – AC power is both – without being tempted to wander rather deeply into technical discussions.  In lieu of doing so here, I refer you to the references for this section which include excellent technical information on AC systems.  However, let me mention for those of you attracted to Option 1’s simplicity and affordability that it is easy to purchase a battery charger (typically, an automotive type) that will share a common neutral AC wire across both sides of the charger.  This offers the opportunity to cross the neutral and hot leads by doing something as simple as reversing the power plug, or perhaps unluckily finding an improperly wired power stand on the dock.  This can do lots of damage, not only to your boat but also to nearby swimmers.  If you opt for a 230V powered battery charger, be sure it is the type with a true isolation transformer inside – the kind where the two windings share no common wire.  These will cost a bit more but are well worth it.

Option 1A:  Onboard High-Capacity Inverter plus Variable Voltage Battery Charger

It is possible to find and install a high-capacity, sophisticated battery charger that can accept any conceivable dock voltage, and use it to charge & float substantial house battery bank(s), which in turn would support a large onboard inverter to supply AC power to the boat.  I have found this – although rarely – on European boats which are already equipped with 24V DC systems, as 24V DC power can support some of the heavier duty jobs such as a high capacity refrigeration system.  While this is another ‘battery charger only’ scenario that can be considered, it is at the opposite end of any “Minimalist” continuum.  These sophisticated variable voltage battery chargers will, by themselves, cost at least as much as a permanently installed transformer.


Option 2:  Portable Isolation Transformer

Suitable for:  Boats with an existing 120V AC system where circuit protection (in the form of circuit breakers on an AC Panel) and wall outlets are already conveniently installed and which the crew wants to use BUT who don’t want the permanency of (or don’t have the room to accept) a larger, heavier built-in transformer system.


Typical Portable Isolation Transformer (Mfgr: Taylor)


Description:  Isolation transformers are essentially two independent windings inside a common case.  One or more voltages can be accepted by the transformer’s primary winding, depending on its construction, but the secondary winding will always produce your required onboard voltage.  With the two windings adjacent to but not connected to one another, the onboard AC is isolated from the dock’s AC.  This provides not only safety for those aboard from an improperly wired dock power stand but also protects the boat from galvanic corrosion if properly installed.

Some Europe-bound yachtsmen are first introduced to portable stand-alone transformers when arriving in Horta, Faial in the Azores, where these are sold by Mid-Atlantic Yacht Services (  This unit is in fact a tool transformer and is representative of a wide variety of such devices used in the UK, so let’s take a look at it. The specs on this unit are:

This transformer would not be 'hard wired' into the boat.  It most likely will live in the cockpit when in use, which is acceptable since it has a plastic case and is waterproof.  You could connect it to the AC Panel by making up an adapter cable or pigtail, connecting one 120V AC outlet of the transformer to the boat’s external AC receptacle, which in turn supplies your boat’s AC panel.  According to MAYS and the manufacturer, the transformer should only be asked to provide about 65% of its full rating for continuous use or 15+ amps of 120V AC.

Disadvantages and Consequences:  First, let’s keep in mind you are only bringing 15+ amps of AC service into your boat, perhaps via your AC Panel with its circuit protection, while most boats are accustomed to having more AC service aboard.  This may especially be true when increased AC service is needed:  imagine wanting to use a small ceramic heater over the winter while you have the AC frig, microwave, dehumidifier and/or water heater on service.  There will be much ‘breaker jockeying’ required!  And let’s not forget that your installed battery charger will need a bit of this 15+ amp service, as well).

You may wonder how we got from 3000 watts of rated capacity to only 15+ amps of sustained service.  It’s important to keep in mind that the intended application of these sealed units is use as tool transformers at construction sites in the UK, where 120V power and isolation protection are stipulated by code for safety reasons. The transformer’s normal use, therefore, is to power multiple smaller motors (i.e. hand tools) for short periods of time; it wasn’t designed with cruising sailors and liveaboard lifestyles in mind.  Also, the unit has a 95% efficiency rating, the other 5% being lost in heat.  So the actual output computation for continuous service is:


3000 watts/120V = 25 amp max capacity

25 amp max capacity X 95% efficiency X 65% continuous duty rating = 15.5 amps

Of course, you can attempt to draw more from the transformer and it will attempt to supply it, but at the cost of a shortened lifespan due to heat build-up and component breakdown.   Another consequence of this approach is that there is no circuit overload protection downstream of any wire run directly into the boat from the transformer, another reason that connecting it to the boat’s external AC receptacle and then using its output via your AC Panel’s circuit breakers is a good idea.  Finally, this approach begs the question of how to power a locally purchased 230V appliance.  You’ll notice I haven’t answered your question about powering that European TV yet.


Option 3:  Permanently installed, variable voltage Isolation Transformer

Suitable for:  Owners who want to draw more AC capacity from their AC panel than described above, who prefer the simplicity and elegance of a built-in system for more (but perhaps not a lot more) money, and/or want to have the protection of an isolation transformer all the time, whether in European or home waters.

Description:  Imagine having one dock power cord on which only the power stand connector is changed, depending on whether the boat is in Europe or back home. That one cord runs from the dock power stand to the external AC receptacle on your boat, after which internal AC wiring is run to the input taps of the newly installed isolation transformer.  A second wire run would then connect the transformer’s output taps to the main breaker on your AC Panel. You can even specify that a transformer be equipped with a switch allowing you to match the transformer to differing dock voltages without any rewiring being needed by you at the transformer, making it a ‘variable voltage’ transformer.  To accomplish this, one would purchase either an off-the-shelf or custom-built transformer, permanently mount it and then reroute the AC wiring as described above.  The benefits are obvious:  adequate AC power, for all the voltages you anticipate, with increased safety to boat & crew, wherever you choose to cruise.  These units are heavier and larger than portable units so a suitable mounting location must be found and they need to be adequately thru-bolted.  To give you a benchmark, our 2.5 KVA transformer had a shipping weight of 105 pounds, including its wooden shipping base.  It came with three welded lugs that would accommodate up to ½” fasteners. We brought it aboard and maneuvered it into a locker using our halyards and winches, and then located it on a bulkhead using small blocks & tackle plus wooden braces inside the locker.

Disadvantages and Consequences:  One disadvantage that comes to mind, as I think back to our own experience, is that both shopping vendors and ordering the unit are required well in advance, with installation still needing to be done before the boat leaves for Europe. This can be tough given the many competing priorities in time and expense - the sheer crush of work – before shoving off.  On the other hand, preparing for AC power onboard is an issue that must be faced at some point, and you will find that careful shopping will reduce your acquisition cost over purchasing once you’ve arrived in Europe.  Moreover, it was great to pull into our first ‘European’ port with the only requirement before plugging into dock power being the purchase of a €2 dock connector.  From Bill Seifert’s excellent Offshore Sailing we learned of Olsun Electrics in Richmond, IL ( and had a potted, U/L approved 2.5 KVA switchable (120V/230V/250V) isolation transformer built for us for about $450 U.S.  For comparison’s sake, note that this is rated to provide a continuous 22 amps of 120V AC, weighs three times as much and is over twice the size of the 3.3 KVA tool transformer described in Option 2.  Since over-demand and the resulting heat are what can break down a transformer, you can appreciate the difference in longevity we might expect from this beefier unit, but at the inconvenience of installing something this bulky.

Olsun and similar manufacturers will build whatever capacity transformer you may choose for your AC panel, so the level of AC service can be as high as you wish to pay for, assuming suitable space and your willingness to live with the weight.  And you may find the rewiring needed to be minimal.  In our case, we were able to simply reroute our existing internal AC wiring which led to our AC panel.  By disconnecting this wiring from the back side of the externally mounted receptacle, it was a simple matter to reroute it to the transformer’s output taps.  Thus, the only new wiring required was from our boat’s external receptacle to the transformer input taps.


To summarize:





Est. Cost ($U.S.)

Materials Req’d

1. 12V 30 Amp Battery Charger

-Eliminates need to run your engine

-Quick, easy & inexpensive

-Brings no 120V or 230V AC service into your boat

$120 (excluding wiring)

Buy when you arrive

-Battery Charger

-Euro dock connector

-25-30M cord

2. Portable Isolation Transformer

(as illustrated by Taylor Model E255 unit)

-Little rewiring required



-Can use AC Panel protection

-Convenient AC use thru-out boat

-Offers isolation protection

-No downstream circuit protection except via AC panel

-May be easy to overwork the unit

-No 230V service into your boat

$300 (plus wiring & connector for AC receptacle)


Buy when you arrive; these are least expensive in Britain and available in many capacities there


-Multiple Euro connectors

-25-30M cord

3. Built-in Isolation Transformer

 with Variable Voltage feature an option (as illustrated by Olsun 2.5 KVA unit)

-Can be custom built to suit needs & for worldwide use

-Uses AC Panel protection

-Convenient AC use; 120V & 230V

-Offers isolation protection all the time

-Requires upfront planning & effort

-Requires space for mounting


-A bit more costly, tho’ not much when all the pieces are added up

$450 (excluding wiring, and also freight if unit is being shipped from mfgr.)


Order and install before leaving; lead time essential for custom build


-Add’l AC internal wire run

-Euro dock plug

-Optional fuses & 230V AC power strip


-25-30M cord

- AC Adapter Pigtail (see below)


The nice thing about these choices is that they don’t span a huge cost envelope.  Our more integrated system was roughly only $300 U.S. more, installed and including shipping, than the cheaper portable transformer option.

Can I Install an Isolation Transformer?  There’s always some risk in tackling a project alone vs. e.g. using an ABYC certified specialist, but probably no greater risk exists than when working with AC electricity.  It can and has killed people who handled it improperly, so if you are less than absolutely certain of what you are doing, I would recommend seeking professional help for the actual electrical hook-up.  This doesn’t preclude you from selecting, ordering, loading aboard and mechanically bolting the unit in place, and also running the wiring needed, all time consuming chores.  Use your ABYC electrician to check over your specifications before placing the order and then later to connect the wiring and test your newly modified AC system.

AC Energy Budgets:  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.  You will sometimes find power stands, especially at the smaller club marinas and in non-marina berthing spaces, offering less service.  Sometimes, you will only be offered 4 amps of 230V AC.  (You’ll also find the nightly berthing fees much reduced as a result).  It’s also possible the entire power stand will be fused for only 32 or even a minimal 16 amps, meaning all power stand users collectively must remain under that threshold.  So first be clear on what essential AC systems you wish to commit to, understanding that your ability to supply them from a shore source will at times be limited and you may need a back-up alternative.  A good example is a boat that hopes to rely on small, inexpensive space heaters for heating aboard.  A relatively simple bulkhead-mounted heater, which requires no AC electricity, could make a good back-up during the Spring and Fall cruising when the dock power stand, if present at all, offers less power than you otherwise would need.

Once you confirm which AC systems you will want to use, next consider how many amps of AC power you will need to draw at any one time.  There is a good reason why your conclusion might not simply be the combination of all your individual AC loads.  For example, if you are willing to throw off the AC breaker supplying your domestic hot water heater when infrequently using the galley microwave at dinnertime, you may save yourself additional size, weight and cost when specifying your isolation transformer.  The same would be true if turning off a small space heater for the few minutes each morning while a hair dryer is in use.


                        Decision Tree for Determining Transformer Capacity

   What are my necessary AC systems while in Europe? Þ

               What are their individual AC amp loads when in use? Þ

                           What will be my likely maximum combined AC amp load? Þ

Result = Minimum Continuous Rating of my Isolation Transformer

(E.g. 120V x Max Amps = Transformer Wattage

for 120V AC boats; vendor can convert to KVA rating)


A final bit of advice:  Try to tackle the issue of supplying AC power early enough that you can consider the custom-build choice, which will include time to identify your transformer specs, and shop vendors and prices.  Given the many competing priorities and ever escalating lists that emerge as one prepares to ‘go foreign’, this is much harder done that said.  If you find yourself struggling to make this a priority, ask yourself:  How many liveaboard systems will I appreciate more than reliable, safe AC power?

We concluded that being able to supply two 10-amp 120V appliances while keeping the battery floating and using a few additional, modest AC appliances was a practical, maximum sustained draw, and we believed this would only require a small amount of ‘breaker jockeying’ from us, whether in the U.S. or Europe.  And that’s how we came to spec a 2.5 KVA transformer.  Other boats will be more electrically complex and demanding than WHOOSH, which has few AC systems, or their crews less tolerant of monitoring breakers and ammeters, and will probably only be satisfied with a larger unit.

 How do I use 230V European appliances once I arrive?  It is now time to think about buying that TV.  And perhaps you lust after a DVD player that plays Region 2 (European) DVDs…or you forgot the clothes iron and would like to press an occasional blouse.  If you choose Option 1 or 2 above, and accepting the reality that you will only have access to a single dockside power stand outlet, you will be restricted to using only those European appliances you can run off a DC-powered inverter, provided you have one.


Permanent Isolation Transformer with

230V Fused Line awaiting Power Strip

(Note acrylic cover over 230V Terminal Strip)


An additional advantage of choosing Option 3, a mounted and hard-wired transformer, is that it offers you access to its input and output taps.  This permits you to lead off a separate multi-conductor wire from the input side of the transformer, which can be fused and then connected to a locally purchased AC power strip that you locate conveniently inside the boat.  Simply and inexpensively fused, the strip will safely supply the same local AC power in the boat that is available at the dock’s power stand.  (Any exposed terminals or connections in this 230V AC line must be shielded from inadvertent contact and protected from salt-water, as well).  To illustrate how quickly this can be helpful, we unexpectedly picked up a dual band GSM cell phone shortly after arriving in the Azores, and found we had an immediate need for 230V AC in order to charge the phone.  (A 12V charger was not immediately available in the stores). With the installed power strip, we were ready.

Slimming Down:  Benefits of an AC Pigtail:  The majority of non-European boats we have seen in Europe were from North America, and most of them had an isolation transformer installed back home before departure.  And just like us, before departure most continued to use their existing heavy gauge yellow power cords, typically 50’ in length but long enough for use in their home marina.  (Using this heavy cord is necessary due to the higher current coming aboard the boat at the lower 120V voltage).  Inevitably, this means that the same heavy power cord remains in use once the boat arrives in Europe, one end just receiving a Euro-standard plug in place of the connector used back home.  This will work fine but there are two problems with it.  First, the typical 50’ length, adequate in well-equipped marinas back home, is often too short for European docks.  25-30 meters of power cord is usually a better length, although occasionally an extension is needed beyond even this.  The second problem is that the heavier, larger gauge wire in the cord makes it more awkward to haul out of a locker, lay out and plug in…only to be hauled back aboard and stored the next day.  This is great as an upper body workout but you’ll soon grow tired of it.  The Euro boats of course use much smaller gauge shore power cords (due to the lower amp loads at higher voltage being brought aboard) and so they typically handle a cord that's light, easily coiled and stowed, but which is also rated for the full 16 amp service at a normal dock power stand.



AC Adapter Pigtail & Extension Cord


Making up your own AC pigtail is a way to enjoy these same benefits PLUS having an additional extension cord available when you need it.  Make up an adapter pigtail by attaching a female 120V AC connector (which will mate with your boat’s existing external receptacle) to one foot of spare cord, and attach a standard Euro 230V male connector to the other end.  Once you have arrived in Europe, shop for a standard 25-30M extension cord with Euro marine plugs (male & female connectors), as commonly found in chandeliers and some DIY stores.  You now have a much easier-to-handle dock power cord, light and easily coiled, which is usually long enough and which mates with your boat’s external receptacle via use of your pigtail.  When you need an even longer cord, remove the pigtail, reclaim your original NA power cord from the locker and, since you installed a 230V Euro receptacle on one end, add it in-line with the lighter 25-30M extension cord. Using or ignoring the pigtail makes both options possible, for only the cost of the Euro extension cord and the connectors mentioned above.

What Happens When Returning Home?  What if you want more AC capacity at your AC panel once you return home, perhaps to a marina environment where a power stand has much greater capacity?  To increase our AC Panel capacity at a later date, the existing AC wiring can simply be disconnected from the transformer and rerouted to the backside of the external receptacle.  However, we would be reluctant to give up the electrical isolation that’s a side benefit of an isolation transformer, which is why we thought about the maximum AC load we felt we needed in the U.S. as well as Europe when selecting our transformer’s capacity.  Adding a permanent isolation transformer has not only given us AC power flexibility, but also decreased the chance that bringing AC aboard would introduce polarity issues, pose a safety risk or damage the boat.  All things considered, this seems to be good value when considering its cost in comparison with its simplicity of use, protection and flexibility.


© Copyright 2005:  Jack Tyler

 For comments or questions on the content of this page contact Jack & Patricia Tyler at "jack_patricia @" (remove spaces from the address when using)