What Is Shore Power? A Plain Guide for Boaters and Marinas

Shore power is electricity supplied to a boat from a fixed source on land, usually through a pedestal on the dock, so the vessel can run its systems without burning fuel in an onboard generator. The boat plugs a heavy cable into the pedestal, and that connection feeds the air conditioning, refrigeration, battery chargers, water heater, and outlets while the boat sits at the slip. In short, shore power is the marina equivalent of plugging an appliance into a wall socket, scaled up for a vessel and built for a wet, outdoor, and electrically demanding setting.

#How shore power works at a marina

Walk down almost any dock and you will see short posts spaced along the finger piers. These are pedestals, and each one is a small distribution point wired back to the marina's electrical service. A pedestal typically carries one or more power outlets, a water spigot, sometimes a lighting fixture, and increasingly a meter. When a boat ties up, the crew runs a shore power cordset from the boat's inlet to the matching receptacle on the pedestal, then switches the circuit on.

Behind that simple act sits a chain of components. Power comes from the utility into the marina's main panel, gets divided across feeder circuits, and lands at the pedestals through breakers sized for each outlet. The cordset is not an ordinary extension lead. It uses a locking, weather rated connector so the plug cannot vibrate loose as the boat moves on the water. For marina operators thinking about the wider picture, our marina software overview shows where electrical metering fits alongside slip and billing workflows.

#30 amp vs 50 amp shore power

The two most common recreational connections are 30 amp and 50 amp, and the difference is more than a number. A 30 amp service in North America is a single 120 volt circuit, which works out to roughly 3,600 watts of capacity. That is plenty for a small to mid size boat running a charger, some lights, and one air conditioning unit. A 50 amp service is usually 120/240 volt with two hot legs, delivering up to about 12,000 watts. Larger boats with multiple air conditioners, electric galleys, and bigger battery banks need that headroom.

• 30 amp: one 120V circuit, around 3,600W, a three pin twist lock connector (often called TT-30 style or the L5-30 locking type).
• 50 amp: two hot legs at 120/240V, up to around 12,000W, a four pin connector rated for the higher load.
• Pushing a 50 amp boat onto a 30 amp pedestal through an adapter limits available power and can trip breakers when big loads start.
• Voltage and frequency differ by region, so a boat wired for 120V/60Hz behaves differently on a 230V/50Hz European pedestal.

Adapters, sometimes called pigtails or splitters, let a boat connect to a receptacle that does not exactly match its cordset. They are useful and common, but they do not create power that the circuit cannot supply. A 50 amp boat plugged into 30 amp service still only has access to 30 amps. Cheap or worn adapters also add resistance and heat at the connection, which is a quiet contributor to dock fires.

#Plugs, cords, and inlets

A boat shore power system has three physical parts that matter at the dock: the inlet mounted on the hull, the cordset that bridges boat and pedestal, and the receptacle on the pedestal itself. The inlet is a sealed fitting that feeds the boat's onboard panel. The cordset carries the load and is the part most exposed to weather, foot traffic, and the constant small movements of a floating dock. Receptacles on the pedestal are weather rated and often spring loaded so the cover closes when nothing is plugged in.

Because these connectors live outdoors in salt air, corrosion is a steady enemy. A green crust on the pins, a connector that feels loose, or a cord jacket that has gone stiff and cracked all signal that the part is due for service. Heat is the warning sign that ties the electrical and safety stories together: a hot plug almost always means a poor connection drawing more current through more resistance than it should.

#The safety story: ESD and GFCI

Shore power deserves respect because the failure modes near water are severe. The most serious is Electric Shock Drowning, usually shortened to ESD. It happens when stray AC current leaks into the water around a dock, often from faulty boat wiring, a damaged shore cord, or a grounding problem. A swimmer in that energized water can be paralyzed by the current and drown without any visible burn or spark. ESD is a leading cause of in water electrocution at marinas and is almost entirely preventable with the right protection and habits.

The technical defense against ESD is leakage detection. A Ground Fault Circuit Interrupter (GFCI) monitors the current going out against the current coming back. If even a small amount goes missing, meaning it is leaking to ground or into the water, the device cuts power fast. On boats, the equivalent device is an Equipment Leakage Circuit Interrupter (ELCI), which watches the whole vessel's AC system. Modern marina pedestals increasingly include ground fault protection at the pedestal level too, so a fault on one boat does not endanger the whole basin.

1. 1Keep shore cords, plugs, and inlets in good condition and replace anything cracked, corroded, or warm to the touch.
2. 2Use GFCI protection on the dock and ELCI protection on the boat, and test these devices on the schedule the manufacturer specifies.
3. 3Never swim near docks that have shore power connected, and post clear signage so guests know the rule.
4. 4Have an annual electrical check that includes a leakage test, since faults develop slowly and silently.

Electrical safety also overlaps with day to day operations: knowing which boats are connected, which pedestals have been serviced, and where faults keep recurring. Our marina safety guide covers the broader picture, and connected IoT sensors can flag unusual current draw before it becomes a hazard. None of this replaces a licensed marine electrician or the relevant electrical code; treat the guidance here as a starting point, not a substitute for professional work.

#How marinas meter and bill shore power

Electricity is one of the larger variable costs a marina carries, and how it gets recovered shapes both fairness and margin. Some marinas fold a power allowance into the slip rate, which is simple but blunt: the boater running three air conditioners all summer pays the same as the one who barely plugs in. Metered billing fixes that mismatch by charging each boat for what it actually uses.

A metered pedestal records the kilowatt hours each slip consumes. The marina then reads those meters, applies a rate, and adds the charge to the boater's invoice. Some operators read meters manually each month and enter the figures by hand; others use connected pedestals that report usage automatically. Either way the principle is the same: metered power billing recovers the actual cost of electricity from the boats that draw it, rather than spreading a guess across everyone. We go deep on the mechanics in our guide to marina metered electricity billing.

In Marine OS, which is in early access with marina operators, metered billing runs through IoT meter readings or custom fields recorded against each slip, so the consumption flows into the same invoice as moorage and other services. That keeps the boater's statement on one page and gives the marina clean usage data to plan against. Operators looking to bring power costs down can pair metering with the ideas in how to reduce marina energy costs, and the slip management tools tie usage back to the right account.

#Frequently asked questions