{ "background": "Power distribution losses in developing economies are a critical engineering challenge, with technical and non-technical inefficiencies causing substantial economic and operational strain. Existing evaluation methods for network interventions often lack rigorous field-based causal evidence, particularly in sub-Saharan African contexts.", "purpose and objectives": "This article presents a novel methodological framework for conducting a randomised field trial (RFT) to causally evaluate the efficiency gains from deploying advanced distribution equipment, specifically composite conductor technology and smart meters, within a national utility.", "methodology": "The proposed RFT design clusters medium-voltage feeders into matched pairs based on pre-trial load and loss profiles, followed by random assignment within pairs to treatment or control. The core statistical model for estimating the Average Treatment Effect (ATE) is a differences-in-differences specification: $\\Delta L{it} = \\beta0 + \\beta1 (\\text{Treatment}i \\times \\text{Post}t) + \\gamma X{it} + \\epsilon_{it}$, where $\\Delta L$ is the change in technical loss percentage. Inference will utilise cluster-robust standard errors at the feeder level.", "findings": "As a methodology article, this paper presents no empirical results from the trial's application. However, the detailed design anticipates a minimum detectable effect of a 1.5-percentage-point reduction in technical losses with 80% power. The framework explicitly addresses implementation challenges such as geographic stratification and blinding of field crews.", "conclusion": "The outlined RFT methodology provides a robust, replicable blueprint for generating high-quality causal evidence on grid efficiency interventions, moving beyond observational studies.", "recommendations": "Utilities and researchers should adopt this RFT design for evaluating capital-intensive network upgrades. Key implementation steps include securing utility operational buy-in, establishing a pre-trial baseline period of at least 12 months, and integrating meter data management systems for automated data collection.", "key words": "randomised controlled trial, power distribution losses, causal inference