Influence of public street lighting on NTL-based impact measurement of rural mini-grids: analytical background and case study in Madagascar

Mini-grids are key for improving electricity access in poor rural areas, but the high collection cost of field data is an obstacle to their developmental impact evaluation. This paper discusses the use of night-time light (NTL) to assess and monitor impacts of rural mini-grids. A positive impact on NTL reveals improvement in electricity access, but it does not necessarily reveal an impact on electric power consumption (EPC), which is key in any theory of change associated with impact assessment of electrification projects. Many NTL-EPC descriptive regressions have been estimated, leading the way to possibly mistaken interpretation of impacts on NTL as impacts on EPC. These equations are often heterogeneous at fine granularity levels. A major source of heterogeneity is related to the role of public streetlamps, which emit vastly more radiance at night per electricity consumption than any other appliance. We propose a framework to disentangle this issue and we apply it to data on a mini-grid project in Madagascar. We show in this case study that overlooking street lighting may bias, by up to a factor 2, the impact of this project on EPC.