"Smart Sub-Metering for Fair Division of Shared Electricity Bills in Multi-Tenant Compound Houses: Serial Cost Sharing on Ghana\u2019s"

"In shared living environments such as compound houses in Ghana, where multiple tenants share a single postpaid meter of the Electricity Company of Ghana (ECG), equitable cost allocation remains a significant challenge. Traditional methods such as the point-based system, equal sharing, and landlord-managed approaches are prone to disputes due to their inability to reflect actual energy consumption patterns. This paper presents a per-room billing system in which a current transformer sensor on each room\u2019s feeder measures per-tenant consumption without requiring load disaggregation, while a low-cost gateway allocates the actual utility bill. The system rests on an empirically exact tariff engine: by reverse-engineering six real ECG bills to the pesewa and reproducing eleven further out-of-sample bills exactly, across a quarterly tariff revision and on nine independent households we establish billing rules absent from the published schedule, including a day-prorated first threshold that varies from 276 to 306 kWh according to billing-month length. Because the inclining-block tariff is convex, sharing a meter creates an aggregation penalty that no budget balanced allocation can spare every tenant; we derive closed-form allocations for proportional, Shapley, and serial cost-sharing rules for any number of tenants and show that a scenario scheme developed from practice is exactly the Moulin\u2013Shenker serial mechanism. On real households and 2,000 simulated compounds, serial allocation keeps the lightest tenant within Gh\u00a2 9\u201312 of their own-meter bill about one-third of the burden under proportional or Shapley allocation, an advantage that persists even as serial\u2019s formal protected zone erodes in larger compounds. A per-tenant day-of-week forecaster halves the error of ECG\u2019s own mid-month estimation convention, so tenants track projected shares before the bill arrives. The results quantify the cost of shared metering up to roughly Gh\u00a2 90 per tenant per month and its structural exclusion of light users from the lifeline subsidy, and position per-room measurement as a low-cost interim remedy."