Before you start
Gather the appropriate supplies and review the specific equipment manual.
- Appliance labels
- Notebook or spreadsheet
- Battery specifications
Step-by-step instructions
Write down each load
Include fridge, navigation electronics, lights, pumps, laptops and any inverter appliances.
Convert usage to watt-hours
Multiply each appliance wattage by the hours used per day; estimate duty cycles for cycling loads.
Add system losses
Allow for inverter and charging inefficiency instead of assuming all energy drawn reaches the appliance.
Compare with usable storage
Convert watt-hours to amp-hours at your actual bank voltage, then apply the battery maker safe usable-depth limits.
Plan for poor conditions
Recalculate for cloudy days and reduced engine or generator charging so the boat has a realistic reserve.
Safety note
Do not size cables, fuses or circuit breakers from a simplified energy budget. Have protection and wiring designed to marine standards.
Key takeaway
Build around daily watt-hours first; then choose storage and charging equipment.
Keep this job on your maintenance schedule
Save the topic as a maintenance task, choose a due date or engine-hour target, and record future service. Free and stored on your device.
Add to my maintenance plannerThis guide is for general education. Follow your equipment manufacturer’s instructions, current navigation guidance and applicable marine safety standards. When uncertain, use a qualified marine professional.