The possibility of energy regeneration, which would be realized with battery systems, was analyzed from the navigation data of the engine ship, and the expected regenerative energy was estimated. The experimental ship is the ocean research vessel Bosei-maru owned by Tokai University, and 6.6 km of navigation data from Suruga Bay to Orito Bay, where the home port is located, was used for the analysis. Since the experimental ship has a variable pitch propeller, the ship speed according to the pitch angle was determined, and the slip with the actual ship speed was obtained, and the regenerable area was specified. From the ratio of the actual ship speed and the ship speed according to the pitch angle of the variable pitch propeller, the regenerative energy amount was obtained assuming the regenerative efficiency in the regeneration. A point where large energy regeneration can be expected during deceleration before stopping was identified, but energy recovery was performed by effortless regeneration according to the deceleration curve without rapid energy regeneration. Thus, it was quantitatively determined that the regenerative energy function can be expected to reduce the energy taken out by 12%. The energy reduction effect obtained by the calculation is a result worthy of sufficient examination.