This power prediction assumes 100% propulsive efficiency, and will need to be reduced to get an accurate engine power estimate. The efficiency may be changed by selecting Efficiency from the Data menu. The efficiency is entered as a percentage.

The power, P, is calculated as follows:

, where

V is the ship velocity;

, the efficiency

R, the resistance.

Hence if the delivered power is required, the efficiency used should be the QPC (Quasi-Propulsive Coefficient).