Despite the fact that there have been a large number of biogas plants built in Ethiopia, to what extent the installed plants have contributed to reducing energy expenditure and increasing income has not been empirically examined. Therefore, this study studied factors that influence adoption of biogas technology and effects on rural household energy expenditure in south Ethiopia. Data were collected from 246 sample households, 123 biogas adopters and 123 non-adopters. Simple random and purposive sampling techniques were used to select sample households. For data analysis, propensity Score Matching and Binary logistic regression models were used. The logistic regression results showed that access to credit (p < 0.01), access to electronic media (p < 0.05), and farm size influenced the adoption of biogas technology positively and significantly (p < 0.05), whereas distance to water sources influenced negatively and significantly (p < 0.05). The average treatment of the treated unveiled that biogas technology adoption reduces household annual energy expenditure on average by about 461 Ethiopian currency per year compared to the counterpart. Reduced energy expenditure enhanced household annual income by reducing money spent on fuel purchases. This demonstrates that the deployment of biogas technology improves rural households' energy supply and increases their annual income. To promote and raise knowledge of biogas technology and increase rural energy security and income, government energy offices, policymakers, and development partners should capitalize on variables influencing biogas technology uptake.