Sub-Saharan Africa hosts 84% of the world’s non-electrified population. For those who are connected, service quality and frequent outages are often named as chief development barriers. Infrastructure improvements and energy access are therefore high on the agenda of African governments and attract large amounts of donor inflows. This paper evaluates a 20-million-dollar investment into the repowering of generation capacities in three decentralized urban grids in Tanzania and the expansion of these grids to surrounding villages. Drawing on two rounds of primary data from 2014 and 2018, we assess outcomes for nearly 500 urban enterprises, 300 urban households, and 1,000 rural households across three district towns. In urban areas, the intervention reduced blackout duration and frequency, leading firms to reduce reliance on backup generators. However, firms' stated willingness to pay for improved reliability remained modest. In the rural part of our sample we find that connection rates in newly connected areas remain low, while access to home-scale solar panels in control villages has increased considerably between the wave. Furthermore, connected households and enterprises consume very little electricity, and we do not observe much productive take up. These findings confirm recent studies on impacts of rural electrification. We conclude by a discussion of whether expanding the grid to rural areas is indeed a worthwhile investment, given that decent decentralized solutions are increasingly available.