The system's overall energy efficiency is defined and is broken into its constituent parts. After a detailed evaluation of the possible energy losses, a three-term formula is proposed in which the most important term is the lifting efficiency that describes the downhole energy losses in the rod-pumped well. When evaluating the energy efficiency of sucker-rod pumped installations, the calculation of the rod pump's useful power plays a decisive role.
The paper shows that the formula most often used in the industry may give inconsistent results under the same conditions. This is why a new formula is proposed that properly describes the useful power exercised by the downhole pump and represents the minimum power requirement for lifting the given amount of liquid to the surface. Through worked examples, the paper shows the advantages of using the proposed formula and recommends its future use for the calculation of the rod pumping system's power efficiency.