The physics
Two high-voltage cables (typically 6.6 kV or 11 kV three-phase) from a shoreside substation to a plug on the ship’s deck or hull. A frequency converter matches the grid’s 50 Hz to the ship’s 60 Hz if needed; most modern installations handle either. The ship’s switchboard takes the feed in parallel with its auxiliary generators, transfers load, then shuts down the generators.
From shore-side voltage to running load, the transfer typically takes 30–60 minutes. Faster changeovers are possible with make-before-break schemes but aren’t standard.
The dominant standard: IEC/IEEE 80005
- 80005-1 - HV shore connection, > 1 kV. Used for container, cruise, ro-ro, tanker, LNG carrier.
- 80005-2 - low-voltage shore connection, < 1 kV. Used for smaller vessels, offshore-support, and fishing.
- 80005-3 - the data interface for safe power management between ship and shore.
Class societies issue a notation (DNV’s “Shore Power”, ABS’s “OPS/AMP”, LR’s “SMPT”) for a vessel that complies with the technical requirements.
The three mandates
1. California: CARB At-Berth
Originally a 2007 rule for container, reefer, cruise, ro-ro. Revised in 2020 to include auto carriers and tankers (phased in 2025 and 2027). The mechanic:
- Once berthed, the ship has a first-connection grace window (up to 3 hours) during which aux generators can run.
- After that, 100 % of power must come from shore or from an approved CAECS (barge-based scrubber / fuel cell etc.).
- Non-compliant hours cost a penalty into the Remediation Fund.
Fleet averaging applies: a carrier that plugs in on 88 % of port calls meets the 80 % fleet-average target even if specific calls fall short.
2. EU: AFIR
Regulation (EU) 2023/1804 mandates shore-power provision at all TEN-T core maritime ports by 31 December 2029 for container, passenger, ro-ro passenger, and cruise ships above 5,000 GT. Annual installed capacity ≥ 90 % of typical demand during the busiest periods.
AFIR is about shore-side infrastructure, not a direct ship-side mandate. It pairs with FuelEU.
3. FuelEU Maritime
Article 6 of Regulation (EU) 2023/1805 requires ships ≥ 5,000 GT in scope to use shore power (or zero-emission technology) for stays of ≥ 2 hours in EU/EEA ports from:
- 1 January 2030 - container and passenger ships at TEN-T core ports
- 1 January 2035 - fleet-wide EU/EEA
Non-compliance penalty: EUR 1.5 per kWh of aux-engine energy delivered during the non-compliant stay (see our FuelEU penalties guide for the broader context).
The savings arithmetic
Fuel avoided during the connected hours:
F_avoided (t) = P_load (kW) × h × SFOC (g/kWh) / 10^6
CO₂ saved on the ship side:
ΔCO2_ship = F_avoided × Cf
CO₂ added on the grid side:
ΔCO2_grid = P_load × h × EF_grid (gCO₂/kWh) / 10^6
Net saving:
Net ΔCO2 = ΔCO2_ship − ΔCO2_grid
A worked example
Container ship, 36 hours alongside, 3,500 kW average hotel+reefer load, aux SFOC 220 g/kWh, MGO (Cf 3.206). EU grid EF 2025 ≈ 230 gCO₂/kWh.
F_avoided = 3500 × 36 × 220 / 10^6 = 27.7 t MGO
ΔCO2_ship = 27.7 × 3.206 = 88.8 t CO2
ΔCO2_grid = 3500 × 36 × 230 / 10^6 = 29.0 t CO2
Net ΔCO2 = 59.8 t per call
Annual: 80 calls × 60 t = 4,800 t CO₂ avoided from one container ship on shore power in the EU. Local pollutants (SOx, NOx, PM) drop to zero during the connection - usually the regulatory driver in urban ports.
In a coal-heavy grid (EF_grid > 700 gCO₂/kWh), the net CO₂ saving shrinks or flips negative, but local pollutants still benefit fully.
The friction
Shore power isn’t frictionless:
- Voltage/frequency mismatch. 60 Hz ships at 50 Hz ports need shore- or ship-side converters; expensive and lossy.
- Cable handling. HV cables weigh 5–10 kg/m; at 60 m a single cable is ~500 kg. Most installations use a cable-management system on deck or on the pier.
- Connection time cost. 30 min of setup per call × 80 calls = 40 h/year - small but real.
- Capacity constraints. A cruise ship can pull 16 MW. The pier substation must deliver that plus ~20 % headroom. In older ports, grid upgrades take years.
- Cost recovery. Shore-power kWh is usually 2–3× commercial grid rates (operator markup, capex recovery). Fuel parity only arrives when bunker prices are high, so the regulatory stick is what drives uptake.
Interactions
- CARB + FuelEU - A CARB-compliant installation (IEC 80005 HV) usually satisfies FuelEU’s technical spec automatically. The obligations are in different regimes but the plug is the same.
- CII - Shore power at berth removes ship fuel from the CII fuel numerator. A 5 % cut in annual fuel translates to a 5 % CII improvement, often the difference between two rating bands for cruise / ro-pax.
- EU ETS - Shore-power hours don’t generate TtW CO₂ on the ship, so they’re out of the ETS scope entirely. Shore-grid emissions sit inside the electricity sector’s own ETS cap.
How to size the trade-off
Try our Cold Ironing calculator - enter load, hours, SFOC, fuel type and grid emission factor; it returns fuel avoided, ship-side CO₂ saved, grid-side CO₂ added, and the net. The CARB At-Berth calculator computes the compliance fraction for a specific port call. The FuelEU OPS calculator handles the EUR 1.5/kWh non-compliance exposure for missed EU berth stays.