Attachment on ZEAT Requirements: Zero-Emission Capable Hybrid Vessels
Click here to access a PDF version of this factsheet.
FAQ on Zero-Emission Capable Hybrid Vessels
1. What is meant by “30 percent vessel power required for main propulsion and auxiliary power operation with zero tailpipe emissions when averaged over a calendar year”?
This means that a minimum of 30 percent of total annual vessel power for both propulsion and auxiliary vessel-systems power must come from a zero-emission tailpipe power source, such as battery-electric propulsion charged by grid-power or hydrogen fuel cells.
2. How do I calculate the 30 percent zero-emission power and provide supporting data to CARB for compliance?
For grid power:
- Use average engine load factors or values provided in Table H-9 of Appendix H of the Initial Statement of Reasons (ISOR)
- Calculate the annual kilowatt hours of diesel-powered propulsion and auxiliary system work.
- Calculate the annual kilowatt hours of electric power used by vessel hybrid system (This may be determined using your hybrid control system data logging or by using a power bill if the power for the vessel hybrid system is separately metered).
- Divide annual kilowatt hours of electric power by the total annual kilowatt hours used (diesel + electric).
A zero-emission capable hybrid excursion vessel has two 400 kW main engines and two 60 kW auxiliary engines. The excursion vessel operator follows steps a.-d. above to check that 30% of power is coming from grid power.
1. The excursion vessel operator uses Appendix H of the ISOR to determine engine load factors for excursion vessels are 0.27 for main engines and 0.40 for auxiliary engines.
2. The operator uses annual operating hours for each engine to determine the total number of kilowatt hours worked by the diesel engines. Multiplying the engine’s power rating, the annual operating hours, and the load factor gives the total energy coming from diesel power.
Rated Engine Power (kWh)
Multiply Engine Power by Operating Hours and Load Factor
Main Engine 1
400 kW ×1500 h ×0.27=
Main Engine 2
400 kW ×1500 h ×0.27=
Auxiliary Engine 1
60 kW ×600 h ×0.40=
Auxiliary Engine 2
60 kW ×100 h ×0.40=
Total Energy from Diesel Power
3. The same excursion vessel operator has collected 12 months of electric utility bills generated by charging the battery on the excursion vessel. The operator gets the total electricity usage for the year by adding up the electric bill from each month.
Electric Utility Bill (kWh)
Total Electricity Usage
4. The excursion vessel operator now knows how much energy is coming from electricity and how much is coming from diesel. Adding those two values together gives the total energy usage for the year.
340,800 kWh from diesel + 150,000 kWh from electric = 490,800 kWh total
To determine the percent of power that was from the electric grid, the excursion vessel operator divides the annual energy from electric by the total energy used.
This comes out to 31%, complying with the 30% zero-emission requirements.
150,000 kWh ÷ 490,800 kWh = 31%
A fillable spreadsheet to assist in these calculations is available on the CARB website.