Superyacht Galley Electrical Power Planning

Why Galley Power Planning Fails

The most common galley power planning failure is calculating total connected load and presenting it to the electrical engineer without applying a diversity factor. A galley with a 60kW connected load does not draw 60kW in operation — a realistic diversity factor of 0.65–0.75 produces a design demand of 39–45kW. Presenting 60kW as the design demand either requires a larger generator than necessary or causes the electrical engineer to reject the specification.

The reverse failure — applying too high a diversity factor and undersizing the distribution system — causes nuisance tripping during intensive service periods and creates pressure to remove equipment from the specification to reduce load.

Step 1: List All Equipment and Rated Power

Start with a complete equipment schedule. For each item, record: equipment name, rated electrical input (kW), voltage, phase, amperage and whether it has a heating element, motor or both. Obtain this data from the manufacturer's data sheets — do not rely on the nameplate alone.

Step 2: Apply the Diversity Factor

Group equipment by load type:

• Continuous load — refrigeration compressors, ventilation fans, warming drawers. These run continuously at near-rated load. No diversity factor applies.
• Cyclic load — combi ovens, dishwashers, induction hobs. These cycle on and off. A diversity factor of 0.65–0.75 is appropriate.
• Intermittent load — coffee machines, toasters, microwaves, mixers. These operate for short periods. A diversity factor of 0.4–0.5 is appropriate.

Step 3: Single-Phase vs Three-Phase

Most galley equipment for vessels above 30 metres is three-phase. Single-phase equipment on a three-phase system must be balanced across phases — an imbalanced load creates neutral current and increases losses. The galley equipment schedule should note the phase connection for every single-phase item and ensure even distribution.

Step 4: Coordinate with the Electrical Engineer Early

Present your equipment schedule with diversity-adjusted demand load to the vessel's electrical engineer as early as possible — ideally before the generator sizing decision is made. Generators are sized on total vessel demand; if the galley demand is not accurately represented in that calculation, the result is either an oversized generator (unnecessary weight and cost) or an undersized one (operational constraint).