Available Energy as a Metric for Sustained Off-Grid Electricity Access

Off-grid electrification is central to achieving universal energy access in sub-Saharan Africa, yet prevailing measurement approaches often rely on static indicators that inadequately reflect the temporal and operational dynamics of electricity service delivery. Built on the foundation of the Multi-Tier Framework (MTF) of energy access, this paper introduces the available energy metric as a time-sensitive measure of electricity service that reflects how reliability conditions and ageing influence realised energy availability over the system’s service life. Using simulated electricity service tiers, the analysis shows that realised energy declines with increased disruptions and continues to decline as supply systems age; for example, a Tier 3 system’s supply could drop from 177.5 Watt-hours per day (Wh/day) at installation to 5.6 Wh/day after five years under the high-degradation scenario. Although higher tiers retain greater absolute energy, proportional reductions remain substantial across all tiers, with Tier 5 declining from 1918.2 Wh/day to 59.9 Wh/day over the same period. Increases in disruption probability reduce available energy consistently across tiers, indicating that reliability conditions influence sustained service independently of installed capacity. The analysis also shows that the gap between nominal and weighted energy is much larger in lower tiers, reaching approximately 28 per cent in Tier 1 compared with about 1 per cent in Tier 5, indicating greater sensitivity to supply timing in lower-capacity systems. These findings show that realised service can diverge substantially from initial tier classification, supporting the use of available energy as a more consistent metric for planning, policy, regulation, and financing of sustained electricity access.