Calculate Your Yacht’s Total Electrical Load
How to Properly Size Your Shore Power Converter
Before selecting a shore power converter, the first and most important step is calculating your yacht’s total electrical load.
Understanding how much power your yacht actually consumes ensures you install a converter that is reliable, efficient, and properly sized for your vessel.
A converter that is too small may overload, while an oversized system can increase cost, weight, and installation complexity unnecessarily.
Why Electrical Load Calculation Matters
Your yacht’s shore power converter must be able to handle peak electrical demand, not just average consumption.
Electrical load varies depending on:
- Climate (air conditioning demand)
- Number of guests onboard
- Galley equipment usage
- Battery charging requirements
- Hotel load during dockside operation
For example, air conditioning alone can represent 50–70% of total load in warm climates such as Florida, the Caribbean, or the Mediterranean.
Step 1: Identify All Major Electrical Loads
Start by listing the main onboard systems that consume power while connected to shore power.
Typical yacht electrical loads include:
HVAC / Air Conditioning
Usually the largest power consumer onboard.
- Chillers
- Air handlers
- Ventilation systems
- Cooling pumps
Typical load:
- 50 ft yacht: 6–12 kW
- 80 ft yacht: 12–25 kW
- Superyachts: 30–100+ kW
Galley Equipment
Modern yachts often include high-power galley appliances:
- Electric cooktops
- Ovens
- Microwaves
- Dishwashers
- Coffee machines
Typical load:
- 3–10 kW depending on usage
Battery Chargers & Inverters
Battery charging systems may draw significant power:
- House batteries
- Engine start batteries
- Stabilizer systems
- Hybrid propulsion batteries
Typical load:
- 2–8 kW
Water Heaters & Pumps
These loads are often overlooked:
- Water heaters
- Freshwater pumps
- Watermakers
- Circulation pumps
Typical load:
- 2–5 kW
Refrigeration Systems
Continuous loads include:
- Refrigerators
- Freezers
- Wine coolers
- Ice makers
Typical load:
- 1–4 kW
Lighting & Electronics
While individually small, these loads add up:
- Interior lighting
- Navigation systems
- AV systems
- Wi-Fi and communication systems
Typical load:
- 1–3 kW
Step 2: Example Electrical Load Calculation
Here is a typical example for an 80 ft yacht:
| Equipment | Estimated Load |
|---|---|
| Air conditioning | 18 kW |
| Galley equipment | 6 kW |
| Battery chargers | 4 kW |
| Refrigeration | 2 kW |
| Water heater & pumps | 3 kW |
| Lighting & electronics | 2 kW |
| Total | 35 kW |
This represents the maximum expected operating load.
Step 3: Add a Safety Margin
Electrical engineers typically recommend adding 20–30% safety margin to account for:
- startup surges
- additional equipment
- future upgrades
- inefficient marina power
Example:
35 kW total load
- 25% safety margin= 44 kW recommended converter size
This ensures reliable operation under all conditions.
Step 4: Consider Peak vs Continuous Load
Some equipment only runs intermittently:
- water heaters
- galley equipment
- battery chargers
However, for safety, converters are typically sized based on maximum possible simultaneous load.
This prevents unexpected overload situations when multiple systems run at once.
Step 5: Check Shore Power Connection Rating
Common shore power connections include:
- 50A single phase
- 100A single phase
- 100A three phase
- 400A three phase (superyachts)
Your converter must be compatible with:
- incoming shore power
- yacht electrical distribution
- onboard voltage requirements
Typical Converter Sizes by Yacht Length
| Yacht Size | Typical Converter |
|---|---|
| 30–50 ft | 12–20 kVA |
| 50–80 ft | 20–40 kVA |
| 80–120 ft | 40–75 kVA |
| 120+ ft | 75–300+ kVA |
These values vary depending on equipment and usage.
Professional Load Analysis
For the most accurate results, review:
- yacht electrical drawings
- load analysis documents
- shore power input ratings
- generator sizing
ANG Marine electricians typically perform this analysis during refits or upgrades.
Final Thoughts
Calculating your yacht’s electrical load is the foundation for selecting the correct shore power converter. A properly sized converter ensures safe operation, reliable shore power connection, and flexibility when traveling between marinas worldwide.
Understanding your vessel’s electrical demand helps prevent overloads, reduce downtime, and protect sensitive onboard equipment.
When in doubt, consult an ANG Converters‘s marine electrical specialist to evaluate your yacht’s power profile and recommend the ideal converter size.
