Shore Power

What is shore power?

Shore power is the electricity supplied to a yacht from a marina, harbour or quay outlet, typically a pedestal beside the berth, through a heavy cable plugged into a dedicated inlet on the hull. Once connected, the yacht's electrical systems run on dockside mains rather than its own diesel generators, which can be shut down for the duration of the stay. The supply covers everything from air conditioning, galley equipment, lighting and entertainment systems to battery charging.

Marina supply standards vary by region. Europe and most of the Mediterranean run on 230V single-phase or 400V three-phase at 50Hz; the United States, the Caribbean and parts of Asia run on 120V/208V at 60Hz. Pedestal sockets are rated by current, stepping from 16A and 32A for smaller craft, through 63A and 125A for mid-size yachts, to 200A or higher three-phase connections for superyachts. As a rough guide, a 32A single-phase 230V connection delivers around 7kW; a 125A three-phase 400V connection delivers roughly 85kW.

Because a yacht built for one regional standard may cruise into another, larger vessels typically carry an onboard frequency converter (manufacturers such as Atlas Marine Systems, ASEA Power Systems and Mastervolt are the common references) that takes whatever the marina supplies and outputs the yacht's onboard standard cleanly and at the correct frequency.

Why it matters for yacht owners

Shore power is the quiet line on the operating ledger. With the yacht plugged in, the generators are off, fuel burn falls to zero on the hotel side, engine-room maintenance hours accumulate more slowly, and the soundscape on board and at the neighbouring berths is transformed.

The environmental and regulatory direction is one-way. Several leading Mediterranean marinas, including Monaco, Porto Cervo, Porto Montenegro and others, already restrict or prohibit running onboard generators alongside, requiring shore-power connection instead. The same "cold-ironing" principle is being rolled out across commercial cruise and cargo ports to cut SOx, NOx and particulate emissions at the quay.

Key facts

• Shore power replaces generator output while alongside, running hotel loads and charging the battery bank from the marina supply.
• European and Mediterranean marinas supply 230V single-phase or 400V three-phase at 50Hz; the US and Caribbean supply 120V/208V at 60Hz.
• Common pedestal ratings step from 16A and 32A for smaller craft, through 63A and 125A, to 200A+ three-phase for superyachts.
• A 32A single-phase 230V supply delivers roughly 7kW; a 125A three-phase 400V supply delivers roughly 85kW.
• Onboard frequency converters from Atlas Marine Systems, ASEA Power Systems and Mastervolt output the yacht's onboard standard cleanly.
• Running on shore power instead of a genset eliminates exhaust emissions and engine noise at the berth.
• Several leading Mediterranean marinas restrict or prohibit running generators alongside, requiring shore-power connection.
• The same principle in commercial shipping is known as cold ironing or alternative marine power (AMP).