48 V vs 96 V Bus Voltage: Which Is Right for Your Electric Boat Repower?
Higher bus voltage cuts cable weight and heat by roughly half for the same power — but 96 V systems carry stricter safety requirements. Here is a practical breakdown for repower decisions.
The bus voltage decision is the most consequential early choice in an electric boat repower because it determines motor options, cable sizing, fusing, and the skill level required for safe maintenance. Getting it wrong is expensive to undo.
At 48 V, a 10 kW continuous installation draws approximately 208 A. That requires 95 mm² main cables to limit voltage drop to under 3% on a 6 m run, and a 250 A fuse at the battery. The cables are heavy, the connections bulky, and the fuse protection expensive. At 96 V, the same 10 kW installation draws 104 A — half the current — allowing 50 mm² cable and a 125 A fuse. The cable weight saving on a 12 m run (there and back) is approximately 18 kg, and the installed cost of smaller-gauge cable and protection is meaningfully lower.
The practical barrier to 96 V is safety classification. IEC 60364 and most national marine standards treat systems above 75 V DC as 'high voltage', requiring insulated-tool work, arc-flash labelling, and — on commercially classified vessels — a formal inspection by a classification society surveyor. For private recreational vessels this is rarely enforced, but it is a real consideration for boatyards offering maintenance and for insurance claims assessors.
The sensible rule of thumb: use 48 V for systems up to 15 kW continuous, especially if the owner intends to do their own maintenance. Consider 96 V (or 80 V, which several manufacturers now offer as a high-voltage-boundary-safe option) for systems above 15 kW where cable weight and heat are material engineering constraints. Above 20 kW continuous, 96 V is almost always the better long-term engineering choice.