Challenges of Integrating Off-Grid Solar Systems with NEPA/DISCO Distribution Networks in Nigeria

Nigeria faces one of the world's most severe electricity access deficits, with more than 90 million citizens lacking reliable grid electricity. Off-grid solar systems spanning solar home systems, isolated mini-grids, and increasingly interconnected mini-grids have emerged as the primary instrument for bridging this gap. Yet their integration with the legacy distribution network operated by Nigeria's eleven electricity distribution companies (DISCOs), successors to the erstwhile National Electric Power Authority (NEPA), remains fraught with overlapping technical, regulatory, financial, institutional, and sociogeographic challenges. This article adopts a systematic review methodology, drawing on peer-reviewed scholarship, regulatory instruments, and grey literature, to identify and analyse the principal barriers to effective integration of off-grid solar systems within the NEPA/DISCO distribution framework. Key challenges identified include deteriorated grid infrastructure, voltage instability, the absence of standardised interconnection protocols, jurisdictional conflicts between DISCO service territories and mini-grid operators, tariff distortions, limited access to long-term capital, weak institutional capacity, geographic and spatial disparities, and inadequate metering coverage. The paper further examines how the Electricity Act 2023 and the revised Mini-Grid Regulations 2023 (updated 2026) represent legislative strides while leaving critical implementation gaps. Policy recommendations are offered with reference to the Sustainable Development Goal 7 (SDG 7) framework and Nigeria's Energy Transition Plan. The findings contribute to the emerging literature on distributed renewable energy governance in sub-Saharan Africa and have direct implications for planners, regulators, investors, and geographers concerned with energy access and spatial equity.