Beyond Net Metering: Design and Performance of a Hybrid Solar Strategy for Cost Efficiency and Security of Supply in Intermittent Urban Grids

Abstract

Distributed generation offers a critical pathway to sustainable urban energy; however, incomplete regulatory frameworks in emerging economies frequently force residential photovoltaic (PV) systems into export-restricted operation. This study quantifies the empirical performance and opportunity costs of a demand-matched, zero-export PV system paired with an Internet of Things (IoT)-managed backup tier. A 54-month longitudinal single-case evaluation was conducted in Arequipa, Peru, utilizing a 1.36 kWp grid-tied array and a 0.6 kWh/day decoupled backup subsystem. Performance was benchmarked against a fully metered pre-PV counterfactual. The zero-export constraint mandated a 96.3% self-consumption index (SCI), capping the self-sufficiency index (SSI) at 37.9% and yielding a utilization ratio (U) of only 24.1% against the site’s technical potential. Economically, a full lifecycle appraisal of the status quo produced a negative net present value (NPV) of −USD 1738. Scenario modeling reversed that outcome under net metering (+USD 862). Net billing at the generation price currently contemplated left the investment short of break-even (−USD 202): the break-even price is PEN 0.317/kWh, some 13% above that reference. The decisive variable is therefore not the remuneration mechanism alone but the price set within it. Furthermore, the decoupled backup architecture mitigated 97.7% of 43 recorded grid outages at a resilience cost of USD 3.2 per protected hour. The headline findings are therefore institutional, not technological: identical hardware shifts from value-destroying to value-creating through the regulatory treatment of surplus energy alone, provided that surplus is priced above the break-even threshold quantified here. We present two replicable sizing rules and propose the U metric to translate regulatory impasse into an internationally standardized reporting parameter, providing an evidence-based roadmap for accelerating decentralized renewable energy in resource-constrained grids (SDG 7, SDG 11).