Grid · Analysis

Plugging in the ships at San Pedro

The twin ports of Los Angeles and Long Beach run the largest shore power effort on the West Coast. Here is how a ship plugs in at the dock, what it costs, and what the harbor air gets back.

BY THE RENEWABLE ENERGY LA EDITORS · FILED SEPTEMBER 29, 2026 · 6 MIN READ ·

How a ship plugs in at the dock

When a ship arrives at a shore power berth, the crew runs heavy cables from the wharf to the vessel and switches its electrical load off its onboard diesel auxiliary engines and onto power from the grid. On the Los Angeles side, that grid power comes from the Los Angeles Department of Water and Power (LADWP), the city-owned utility; on the Long Beach side it comes through Southern California Edison. The connection points sit in vaults and outlets built into the dock, and each berth has to be wired for the vessel types that call there.

That load is not small. A single large container ship at berth can draw several megawatts just to keep its systems running, and a cruise ship at the World Cruise Center in San Pedro can draw more, roughly what a small neighborhood pulls on a hot afternoon. It is the reader's situation in reverse: the same wires that serve harbor homes now have to serve the ships too, which is one reason the buildout has taken years and leaned on the utilities to add capacity.

What it costs, and who pays

Installing shore power is expensive. Wiring a single berth runs into the millions of dollars, and across both ports the total public investment is on the order of hundreds of millions at last public report, paid through port budgets, state and federal grants, and utility programs. Ships also have to carry the equipment to connect, a cost borne by the shipping lines and, indirectly, by the goods that move through the harbor.

Who ultimately pays is a fair question with an honest answer of 'several parties, in pieces.' The ports are landlords that earn revenue from terminal leases and fees rather than city tax dollars, so much of their share comes from operations. Grants from the California Air Resources Board and from federal clean-ports programs cover parts of it. And because the electricity flows through LADWP and Edison, a sliver eventually touches ratepayers, though the ship load is billed to the terminals, not spread quietly onto your home bill.

The air-quality return

Health is the reason the state pushed this. Diesel exhaust at berth carries fine particulate matter (soot small enough to lodge deep in the lungs), nitrogen oxides that help cook the basin's ozone, and sulfur oxides, and the harbor communities of San Pedro, Wilmington, and West Long Beach have carried more than their share of it for generations. Los Angeles air already fights an inversion layer that traps pollution against the mountains, worst in late summer and early fall when heat and haze settle in, which is right about now.

Shore power removes the great majority of a plugged-in ship's at-berth emissions, for the plain reason that the diesels are simply off. California's At Berth regulation, run by the Air Resources Board, requires most container, refrigerated, and cruise vessels to control their emissions at the dock, either by plugging in or by using an approved capture system, and it has been phasing in tankers and vehicle carriers through the mid-2020s. The catch is honest: the rule covers time at berth, not the approach or the anchorage, and compliance depends on both the berth and the ship being equipped, which is not yet true everywhere.

Worth watching this month

1. Watch the California Air Resources Board's At Berth compliance reporting, where the phase-in for tanker and vehicle-carrier berths continues through the mid-2020s and is the part most likely to slip.

2. Watch LADWP's harbor-area capacity and rate filings, since adding shore power load is a routine but real draw on the local grid.

3. Watch the Port of Los Angeles and Port of Long Beach board agendas for shore power berth contracts and grant awards, most of which are routine but a few of which signal a new terminal coming online.

4. Watch state and federal clean-ports grant windows, which open and close on their own schedules and fund much of the remaining buildout.

5. Watch the late-season heat and inversion forecasts from the National Weather Service, since the worst air days are when the at-berth savings matter most.

Where this dispatch reads

California Air Resources Board, At Berth Regulation, ww2.arb.ca.gov/our-work/programs/ocean-going-vessels-berth-regulation, State government rule requiring container, cruise, and other vessels to control emissions while docked; the source for what is required and when.
U.S. EPA, Ports Initiative, www.epa.gov/ports-initiative, Federal government overview of port emissions and shore power technology, for the health and pollution context.
Port of Los Angeles, Alternative Maritime Power (AMP), www.portoflosangeles.org/environment/air-quality/alternative-maritime-power-(amp), The LA port authority's own page on how its shore power program works and which berths are equipped.
Port of Long Beach, Shore Power, polb.com/environment/shore-power, The Long Beach port authority's page on its shore power buildout and Green Port program.
Los Angeles Department of Water and Power, www.ladwp.com, The city-owned utility that supplies the electricity to the Port of Los Angeles berths.
California ISO (CAISO), www.caiso.com, The grid operator that manages the statewide grid the harbor and its ships draw from.

Questions readers have asked

Is shore power the same as cold ironing?

Yes. Cold ironing is the older sailor's term for a ship shutting down its own engines at the dock and drawing power from land instead. Shore power is the plain modern name for the same thing.

Does plugging in the ships raise my electric bill?

Not directly in any obvious way. The ships' power is billed to the terminals through LADWP or Southern California Edison, not spread onto home accounts. The grid upgrades that support the harbor are part of the utilities' broader costs, which is a slower and more diffuse effect.

Do all ships at the ports plug in?

No, not yet. The At Berth rule covers most container, refrigerated, and cruise ships, with tankers and vehicle carriers phasing in, and it applies only while a ship is tied up at an equipped berth. Vessels waiting offshore or at berths without the gear still run diesels.

Where does the electricity come from?

On the Los Angeles side it comes from LADWP, the city-owned utility; on the Long Beach side it comes through Southern California Edison. Both draw from the wider California grid managed by the state's independent system operator.