The advantages of a shore power connection
Power demands on a boat are directly correlated with the level of comfort desired by the boat's occupants. Refrigerators, freezers, electric hobs and the use of computers are quite commonplace on most boats nowadays, and when docked in a marina, connecting to shore power is the best way to supply your boat with 230 volts, without worrying about solar panels, wind and weather, and without the sonorous humming of a generator disturbing the peace. Adding shore power to your boat is an important part of your on-board energy management system. And that means not only more comfort, but above all safety. Because before you set sail again the next day, you should make sure that your batteries are all fully charged.
Why shore power is important
Anyone who wants to retrofit a boat shore connection benefits in two ways. Firstly, 230V is available, which makes life on board much easier, and secondly, your onboard batteries will be fully charged, which means that adding a marina shore power connection to your boat is a massive step in the right direction towards better seamanship. A power failure at sea can have serious consequences, and result in important navigation equipment such as chartplotters, depth gauges or autopilots failing. Not only that, if the fridge loses power, those cold beers won't stay cold for long! Connecting your boat to shore power is the most common, simplest and also the cheapest alternative to ensure the power supply on board stays strong. But: What is shore power for boats actually? To put it simply, it's like plugging your living room into a giant extension cord from the power grid. However, there is a lot more to consider when installing on board.
Planning and preparing the upgrade
The first step is to clarify the energy requirements on board. Which suppliers should be connected directly via 230 volts? How many sockets must be installed on the boat? What capacity do your boat batteries have and how much charging current should they be charged with? And then, of course, there is the question of where the connection can be installed on board. You should also take a look at the land-based charging station even if there are unlikely to be any major surprises there. In European marinas, the so-called CEE power distribution is the only authorised system for boat shore power.
1. Requirements: What is required for installation?
If you want to add a shore connection to your boat you first need three components for a secure connection between the power column in the marina and the boat. Firstly, there is the three-pole shore power cable, or ship-to-shore cable, which should be UV- and seawater-resistant, abrasion-proof and flexible. This cable is connected with the distinctive blue CEE shore power plugs but can also be purchased as a set. The female connector for the on-board power inlet (or receptacle) is fitted with a spring-loaded cover and a latch or a small pressure lever to ensure that the plug connection does not come loose on its own. This robust connection is also protected against water from the rain. The third component is the shore power connection, also known as the ship-to-shore power connection or shore power coupling, which is permanently installed on the boat. Bellow deck, further installations such as a switch box with fuses and a galvanic isolator or isolating transformer are required. In order to distribute the shore power on board as required, only sockets suitable for marine use need to be installed. A charger suitable for the battery capacity and on-board power supply voltage is also required to charge the boat batteries.
2. Checking the on-board electrics and existing tech
Now is the time to take a look at your on-board electrics. In an ideal world, there would already be drawings of the previous installations, which should be supplemented by a boat shore connection wiring diagram. On older boats, which have already passed through the hands of several owners, many of whom will have, no doubt, tinkered with the electrics, the cables might look a bit of a mess. In which case, proceed with caution. Poor electrics or the use of inadequate materials is the most common cause of fires on boats.
3. Gathering necessary components (plugs, cables, fuses)
In European marinas, t0/>shore power supply with CEE plugs is not only standard but also mandatory. The blue CEE plugs always have three poles, which has a major advantage over the standard household earthing contact plugs (SchuKo). This is because the position of the two current-carrying poles is always clear. The use of other plugs can be difficult to explain to insurance companies in the event of damage. Anyone who wants to retrofit shore power should therefore look for high-quality components that promise durability, but above all safety, and have proven their suitability for the maritime sector.
The so-called CEE shore connection, i.e. the on-board plug, is also 3-pin. The housing for the boat shore power connection is usually made of high-quality, impact-resistant and splash-proof polyamide, but more sophisticated stainless steel versions are also available.
One question remains: Which cable for shore connection is the most suitable? Only a special cable that is resistant to seawater, oil, grease, petrol and UV rays may be used for the 230V power supply. It must also be abrasion-resistant and flexible. So stay away from cheap DIY store goods for the household! Up to a cable length of 15 metres, a three-core cable with a cross-section of 1.5 square millimetres is sufficient. A cross-section of 2.5 square millimetres is required for cable lengths of 25 metres or more. So, once you've got the power on board, now a cable, which should not be longer than one metre, must be laid to the fuse box, from which all 230V cables branch off. Due to the wet and general electrical safety on board, a residual current device (RCD) must be installed here.
4. Overview of expected costs
If you want to add shore power to your boat, you can expect manageable costs For a medium-sized boat, such as those widely used in the sport boat sector a dimensioning of the components with a load capacity of 16 amps is usually sufficient. At 230 volts, this corresponds to an output of around 3680 watts. By way of classification: A fan heater usually consumes between 1000 and 2000 watts, charging a laptop around 65 watts and charging a smartphone sometimes less than 10 watts.
Affordable land connection sockets are available for less than 20 euros, while high-quality versions with a chrome-plated surface or made of stainless steel cost between 100 and 150 euros. The length and cross-section of the cable are important. For example, a 3-pole CEE extension cable with a rubber sheath including fitted plug and a length of 20 metres with a cable cross-section of 1.5 mm is available for less than 50 euros, while the same cable with a cross-section of 2.5 mm costs just under 80 euros.
An galvanic insulator costs from 120 euros, with a further 100 euros for the fuses. Then there are the costs for cables, connections and sockets. All in all, the components cost from 300 euros.
Jens' tip: How to plan the upgrade
If you want to add shore power connection to your boat, you should familiarise yourself with DIN EN ISO 13297 ‘Small craft - Electrical systems - Alternating current installations’ a standard that deals with personal protection, the safety of electrical systems and fire protection on small craft. DIN EN ISO 13297 regulates how to retrofit shore power and connect shore power.
However, if you are not a trained electrician, it is better to leave this work to a specialist, who should also draw up a so-called shore connection diagram for the boat - for any subsequent repairs. To save costs, you can carry out various preparatory work yourself if you want to retrofit shore power to your boat . For example, calculate which cable is required for shore connection install the junction box, fit the fuse box, install the charger - and lay the cables to the sockets.
Tech for retrofitting a shore connection
Installing the shore power connection
First things first: electricity is not something for amateurs to 'have a go' at. Even if retrofitting a shore connection to a boat is not ‘rocket science’, only those who have the appropriate expertise should dare to do it themselves - for insurance reasons alone. First of all, of course, you need to find the perfect place to install the shore power connection, ideally protected from the weather. On most boats, it is located at the stern or in the cockpit. The fuse box, from which the 230V cables are laid, should also be located not far from the connection, below deck. For documentation purposes, we recommend sketching the installation layout and labelling it Circuit diagram Shore connection boat. The installation can then begin.
Safety measures and preparation
Before you can connect the shore power all components should be installed. When selecting the 230V cables it is important that no cables with rigid wires are used, as they can break due to vibrations. The cables must consist of individual flexible wires, known as strands, which in turn are fitted with ferrules. Solder connections are unsuitable. The cross-section of the 230V cable must be at least 2.5 square millimetres. If you want to retrofit shore power to your boat, you should run the cables to the sockets through a flexible protective conduit that is temperature-resistant, UV- and oil-resistant and waterproof. At the sockets, ensure that the deck seal runs into the housing from below so that no moisture can run along the cable into the interior.
Step-by-step instructions for installation
Once all the sockets have been installed and the power cables have been laid in their protective conduits, professionals can start connecting the cables. It is important to switch off the power on the boat. Switch off the main switch and disconnect the batteries for safety reasons. The boat must also not be connected to shore power. There should be no more than one metre of cable between the boat shore power connection and the fuse box. All 230V lines now come together in the fuse box, protected by a so-called fault current circuit breaker (also known as residual current circuit breaker or personal circuit breaker). A circuit breaker is mandatory if you want to retrofit boat shore power.
Integration into the on-board electrical system
When fitting a shore connection for the boat, a cable is laid from the fuse box to the battery charger, which feeds the onboard batteries. Modern, high-performance battery chargers can charge several battery banks simultaneously, for example the starter battery and the service battery, and are suitable for almost any battery type - including lithium-ion batteries. In a final step when fitting the boat shore connection, the protective conductor of the alternating current must be connected to the ship's earth. This is a regulation. The negative terminal of the on-board battery or the engine can be used as the ship's earth, or the hull in the case of metal yachts. If the boat is connected to the shore power supply, a galvanic current flow may occur.
And this must be avoided. This is because this current can trigger an electrochemical reaction in which metal parts such as propellers, rudders or sea valves corrode. There are two ways to prevent galvanic corrosion. The cheaper one is an galvanic insulator, also known as a ‘zinc saver’. But how does a galvanic insulator on a boat actually work? The galvanic insulator is installed in the earth line between the boat and the shore power network and blocks the flow of current through small direct voltages, which are the main cause of galvanic corrosion, but allows larger alternating currents to pass through. The alternative is a isolating transformer, which forms a protective separation in the boat shore connection between the marina's power supply and the on-board power supply. It is the conceptually cleanest solution - but also the most expensive.
Common mistakes
The most common errors when installing shore power boot lie in the choice of insufficient or mismatched components. For example, no cables with different cross-sections may be combined, because a cable cross-section that is too thin leads to voltage losses. In the worst case scenario, only 200 volts instead of 230 volts arrive on board. Another common source of faults are poorly processed connections or corroded cables. It is important to protect the electrical system in accordance with the requirements. A combined RCD/LCB suitable for the amperage (e.g. 16A) is a safe bet. An overvoltage protection system is also available to mitigate voltage peaks in the shore power that could damage the electronics on board.
Jens' tip: Don't cut back on the electrics!
Even if you have hours and hours of sailing under your belt, which would mean you should be able to handle almost any on-board task unfortunately, when it comes to electrics, this isn't always the case. Electrics are such an issue, especially when it comes to 230 volts - as with shore power, that if you get a shock it can be fatal. A blown fuse or the wrong, poor quality material can cause a fire. You don't want that in the middle of the ocean. That's why we have two rules on board: Firstly, if in doubt, ask a specialist. And secondly, don't save money in the wrong place.
Because if you buy cheap, you end up paying twice. Unfortunately, the previous owners of our Moody 425, built in 1988, did not always take this to heart. And now we have to, literally, untangle the mess ) of their wiring). If there is a tricky, safety-relevant task that should be carried out on board, better to leave it to the experts, even if it does put a dent in your ego and your wallet.
Plug for shore connection
Sockets for shore connection
Safety and maintenance
If you have installed your shore power connection for the boat safely, you can now connect the appliances to the installed 230V mains and charge your batteries at the same time. However, care must always be taken not to operate too many ‘power guzzlers’ at the same time in order to prevent overloading the on-board power supply. An installed energy meter can help to keep an eye on current consumption. Bear in mind that 230 volts in the damp environment a boat always represents a risk - albeit a calculable one. Nevertheless, it is necessary to check the shore power connection regularly. Above all for moisture.
Protection against overload and short circuits
The shore power connection must be checked regularly to avoid damage on board or hazards such as fires or electric shocks. A look at the FI circuit breaker, which protects against electric shocks and residual currents, is therefore just as appropriate as a check of the circuit breaker, which in turn protects against overloads and short circuits. If visual changes are recognisable, for example due to excessive heat development or moisture, the circuit breakers should be replaced as a precaution. The best protection against overloading and short circuits are high-quality components such as water and UV-resistant cables and cleanly connected lines.
Regular inspection of the system and replacement of worn parts
All cable connections should be checked regularly for corrosion. It is also advisable to check the cables for kinks or breaks. If the cables become unusually warm, they should be replaced. The same applies to the fuse box. Loose screws or heat developmentmay indicate problems. In most cases, however, faults can be traced back to the shore power cable, caused by improper storage or loads on the jetty. The following applies in all cases: Worn parts must be replaced in good time.
Tips for safe use on board
If you have installed the circuit breakers and the galvanic isolator professionally, you are actually on the safe side. It is unlikely that the isolator is not working properly. It cannot be destroyed except by lightning. How does a galvanic insulator on a boat work again? To test whether the lt;strong>insulator is working, the voltage can be measured with a multimeter in diode test mode. In both directions it should rise to around 0.9 volts and remain there. After the capacitor has been discharged, it should rise again from 0 to the previous value.
Cables and accessories for shore connection
Jens' overview and personal tip
Summary of the key points
A shore power connection is part of the basic equipment of a cruising yacht. Admittedly, we rarely use it. But that's because we're hardly ever in a marina and produce enough electricity from our solar panels. This is usually possible in the Mediterranean and the Caribbean. Nevertheless, the shore power connection is an important backup. During a period of bad weather lasting several days, our lithium batteries were almost drained and we wanted to start the engine to generate power via the alternator to bridge the gap. But the device was defective. Without the shore power connection we would have been lost. Consequently, we were able to borrow a portable generator and connect it to the shore power connection and the situation was saved.
Selection guidance for boat owners
In most areas, a shore power connection is completely sufficient for the supply of the on-board batteries. For example, anyone sailing in the Baltic Sea and heading for a harbour in the evening rarely needs alternative energy sources such as solar or wind. And in an emergency, there is still the alternator. On site in the harbour, there are usually pillars with sockets at the berths, mostly standardised for 16 or 32 ampere connections. The boat is connected with a suitable shore power cable. Depending on the harbour, payment is made by inserting coins, cards or apps. Once activated, electricity flows for on-board devices such as lights, refrigerator or chargers. Always pay attention to this: Cables and adapters must comply with the requirements to ensure safety.
Frequently asked questions (FAQs)
About Jens:
Jens Brambusch, born in 1972, worked as a reporter for the Financial Times Deutschland and the business magazine Capital. He has been living on a Moody 425, the Dilly-Dally, since 2018 - initially in the Mediterranean, and in 2022 he set off for the Caribbean with his girlfriend, dog and cat. Since then, it has travelled almost 30,000 nautical miles. Brambusch has written several sailing books, is a regular contributor to Float magazine and publishes videos about his sailing adventures on the YouTube channel ‘Sailing Dilly-Dally’.