IEEEContribution: This article analyzes the correlation between users' digital competencies and their tendencies to successfully complete energy sustainability massive online open courses (MOOCs). In addition to reviewing whether digital competencies are a predictor of the effective completion of the course, this article analyzes whether participants acquire higher levels of digital competence through interaction in the course. Background: Completion rates of MOOCs typically range between 5% and 8%, with respect to registered participants. According to the literature, low rates may be due to factors such as students' lack of motivation or digital competence limitations. Research Questions: RQ1: Is there a correlation between the level of digital competence declared by the participants and their tendency to successfully complete the MOOC? RQ2: Does participation in a MOOC improve participants' digital competencies? Methodology: Two surveys, one pretest and one post-test (before and after the MOOCs), were applied to assess the digital competence levels of the participants. The total population of participants in the 12 MOOCs was 123,124 unique users, from which 9075 participants (pretest)--7.37% of the universe--and 6029 participants (post-test)--35.70% of the universe--were extracted as a sample. To determine its internal consistency, an exploratory factorial analysis was performed on both instruments and a Cronbach's alpha greater than 0.8 was obtained in all of its dimensions. Findings: A significant level of moderate to high correlation between the declared levels of digital competence and the trend toward successful completion of the MOOCs under study was observed. However, a significant increase was not demonstrated in the levels of digital competence acquired in the interaction with MOOCs. Conclusions: The level of digital competence of a participant in a MOOC was a valid predictor of their tendency to finish it. Although no increase in the levels of digital competence acquired through MOOCs was demonstrated, this may be because the subject matter of the MOOCs was alien to the indicators and dimensions of the digital competence. Further research could analyze the effectiveness of MOOCs in terms of digital competition at the acquired levels of competition.