Current lower oil price has thrown energy efficiency into sharp focus. The author believes that the drilling industry should have a responsibility to minimize cost and maximize efficiency in all circumstances. The thesis develops methods to quantify energy consumed for drilling as a potential drilling optimization. For this purpose, energy consumption models are developed and empirical measurements are made to track performance against the model. General energy consumption concepts are used to develop three mathematical energy consumption models for each of the major energy consumers of a rig: mud pumps, top drive and draw-works. Thesis includes justification and explanation of developed models with supporting theory. The research also includes a chapter dedicated to models confirmation, verification and validation, where modeled fuel consumed results are cross referenced against the real fuel consumed data. These steps gradually prove accuracy of the created energy consumption models. As a result, the thesis proves the possibility to use the drilling parameters to accurately calculate the energy consumption for each phase of rig activity. Thesis also offers to improve models by enhancing drilling data quality and drilling rig specifications. Additionally, the author suggests the further application of the research in the area related to drilling energy efficiency KPIs.