Shore Power Supply

How Does Shore Power Work on a Boat?

Shore Power for Boats: Accessories and Connection Options

To safely and reliably connect your boat to shore power, you need the appropriate accessories. These include special sockets, adapters, cables, electrical distributors, and extension cords. For boats with low to moderate power requirements, a 16 A socket is usually sufficient. It is robust and waterproof. For energy-hungry yachts with high consumption (up to 100 A), a 32 A socket is recommended. The higher capacity ensures you can run multiple electrical devices simultaneously—such as refrigerators, heaters, or power tools—which are increasingly standard on modern boats. 

Harbor and marina connections typically feature a three-pin CEE socket. These connections are secure, weatherproof, and easy to use. Cables connecting the boat to shore power are usually 20–30 m long and have a durable PUR (polyurethane) outer jacket to protect the internal 3x1.5 mm² or 3x2.5 mm² wires. 

On board, a compact, waterproof CEE plug with cylindrical contacts or a Marinco plug is usually installed, often at the transom or in the cockpit. hese plugs include a cover and threaded ring to secure the connection to the boat socket. You can also connect an extension cable or cable reel directly to shore power —for example, to run tools or a heater without routing through the boat’s onboard network. Ensure any extension includes a built-in circuit breaker. 

For using 230 V shore power via the boat’s network, currents over 16 A require an AC distribution panel with a residual-current (RCD) and circuit breakers for short-circuit and overload protection. Some models also provide reverse-polarity protection and integrated fire protection switches, which can quickly disconnect both poles in case of dangerous faults (loose connections, screws, etc.) that a standard RCD might not detect.

Safety First: 230 V shore power can be dangerous. All distribution components—metal housings of chargers, inverters, heaters, and onboard sockets—can pose risks of leakage, short-circuits, corrosion, or electric shock. Always check that all components are certified, rated for marine use, and resistant to oil, grease, fuel, water, UV, abrasion, and cracking.

Plugs, cables, and sockets can be purchased separately and installed yourself. But remember, if you are unsure, always consult a professional. SVB also offers pre-assembled cables that save time and effort. Before installation, carefully check what type of connections are present both in the harbor and on your boat.

How Is Shore Power Grounded on a Boat?

Grounding: A Critical Safety Measure

Proper grounding is crucial when connecting shore power. Note that “ground” and “chassis/neutral” are not the same and should not be connected directly. Electricity is invisible, and contact is already dangerous. Ensure all metallic masses are safely grounded to minimise the risk of electric shock.

Should You Ground the 12 V Onboard Network?

Impact on Galvanic Isolators and Transformers

Low-voltage systems on board (12 V or 24 V) are generally safe and not lethal. The negative battery pole is already grounded through the inverter, propeller shaft, and hull to the sea. Additional grounding is usually unnecessary.

However, low-voltage systems carry a fire risk because higher currents are involved. Onboard 230 V systems run AC and DC networks simultaneously, both grounded via the yellow-green shore power cable. European standards require the grounding of both systems to be connected— unless a main breaker, residual-current device, or isolation transformer is installed at the AC input.

Connecting both ground systems introduces the risk of galvanic corrosion between metals above and below the waterline. The simplest and most cost-effective solution is installing a galvanic isolator immediately behind the shore power socket.

Using separate ground connections can eliminate galvanic corrosion, but high-quality protective devices must be installed to ensure human safety.

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