Energy Densities of Petrol and Batteries
All modern batteries have significantly lower energy densities than petrol or diesel.
However, a considerable proportion of the energy stored in petrol is lost during the combustion process. Electric drive systems can also use propellers more efficiently owing to their more suitable torque characteristics. Overall, electric drive systems can use the power made available to them up to 10 times more efficiently on water.
Gravimetric energy density of various energy sources in comparison [Wh per kg]
And yet the preconception remains that an electric drive provides significantly less propulsive power than a combustion engine. For this reason handling available energy with great care takes on particular significance in the case of electric drives. That's why overall efficiency that takes account of all losses including propeller loss is the most important indicator of performance for an electric boat motor.
The Torqeedo Ultralight travels up to 40 km – while the power supplied by its batteries corresponds to the energy content of only 26 grammes of petrol. That is efficiency and the careful use of resources.