The energy consumption of a backhoe during digging operation is the sum of the energy due to earth pressure and backhoe motion. The authors' previous studies have revealed the earth pressure model on the arc trajectory, but not on the horizontal trajectory, which is often used in normal digging operation. Moreover, in order to optimize energy efficiency, a comparative experiment of energy consumption was carried out for the multiple excavation trajectories involving horizontal direction. However, since the theoretical model of earth pressure has not been completed, the experimental data obtained from the testbed is used as a reaction force. If it can be confirmed that the reaction force of the horizontal trajectory can be calculated with a theoretical value, the energy efficiency can be calculated from the excavation trajectory without experiment. In this study, the earth pressure model for the horizontal trajectory was confirmed, and the method for the evaluation of energy efficiency was verified using the theoretical values.