Urban Housing Density, Solar Photovoltaics, & the Case for Grid-Tied Energy Augmentation in Nigeria: An Analysis of Residential Energy Demand and Solar Feasibility

Nigeria confronts a deepening energy and housing crisis: a documented housing deficit exceeding 28 million units coincides with severely constrained electricity access—only ~13% of Nigerians report a reliable national-grid supply and ~86.6 million people remain without electricity. Concurrently, utility-scale solar PV costs have fallen sharply (levelized cost down ≈ 90% between 2010-2023), prompting interest in rooftop PV as a leapfrog solution. This paper assesses the technical and spatial feasibility of independent rooftop PV systems as a primary supply strategy for middle-income, multi-family urban housing in Lagos, Abuja and Port Harcourt. Using two years of field-validated consumption monitoring across representative flats, appliance inventories, seasonal disaggregation and solar insolation data, we find typical 2 - 3 bedroom urban flats consume 30 - 50 kWh/day, with roughly 50% of demand attributable to space cooling. Translating demand into generation and storage requirements yields a per-unit rooftop sizing need of ~18 kWp (≈100 m² roof area). Sensitivity analysis across three demand scenarios (30/40/50 kWh/day) and city-specific sun-hours shows the spatial infeasibility conclusion is robust: for a standard six-unit apartment block the aggregate PV requirement exceeds available roof area by a factor of ~2.0 at the mid scenario and ~2.75 at the upper bound. Structural assessment indicates a full six-unit rooftop PV array imposes an additional dead load of ~0.20 kN/m², a ~26% increase over the minimum imposed roof load allowance of 0.75 kN/m² when applied as a permanent load. Comparative analysis of alternatives shows mini-grids require large land footprints (illustrative mini-grid: ~1250 m² per dwelling for a 2 MWp system serving ~240 units on 5.5 ha). We define grid-tied augmentation as building-level PV sized to meet ~50% of daily demand with remainder from the public network, and distinguish it from net-metering/net-billing (billing mechanisms) and community hybrid mini-grids (shared assets). Policy implications are threefold: 1) rooftop PV as a primary supply for multi-family urban housing is generally spatially and structurally infeasible at current demand levels without major building redesign or demand reduction; 2) pragmatic near-term strategies include grid-tied