Groundwater irrigation is critical for supporting food security, rural livelihoods, and economic development in the Eastern Indo-Gangetic Plains (EIGP) of South Asia. However, groundwater resources in the EIGP remain underutilized due to farmers’ reliance on expensive diesel pumps for accessing water. This study uses primary household survey data from the Terai region of Nepal to analyse the drivers of variability in irrigation access costs across farms, and how these cost variabilities influence agricultural outcomes. We employ an endogenous switching regression model to assess the impacts of pump ownership on farm productivity and profitability. Our findings show that pump ownership reduces irrigation costs rice and wheat cultivation, the region’s two major crops, by 72 % and 76 %, respectively, and increases rice and wheat productivity by 37 % and 20 %, respectively. Our findings provide empirical evidence of the positive impact of technology ownership on agricultural productivity and highlight the opportunities for policy interventions focused on improving performance of existing technologies for enabling long-term sustainable intensification of irrigated agriculture in the EIGP.