Running Marine Air Conditioning from Lithium Batteries
Calculate kWh, inverter, battery and solar requirements for running boat air conditioning from a lithium battery bank.
Air conditioning can dominate a liveaboard energy budget.
A small efficient unit drawing 700W for three hours uses:
700 x 3 = 2.1kWh
If the same unit runs eight hours:
5.6kWh
Design around startup surge, inverter size, DC current, BMS current, cabin insulation, target temperature, ambient temperature, compressor modulation, number of cabins, shore power, generator use and solar availability.
Lithium makes battery-powered air conditioning possible, but it does not make the energy free.
Turn the appliance into a daily energy figure
The peak wattage tells you whether the inverter and BMS can start the load. Runtime tells you what it does to the battery bank. Treat those as separate checks, then include conversion losses and the loads already running aboard.
- Measure typical watts and realistic hours per day, including standby use and cycling loads.
- Check startup surge and maximum simultaneous current against the inverter, BMS and cabling.
- Test the result against a poor-solar day and preserve a reserve for essential navigation and safety loads.