"background": "Distribution transformer losses constitute a significant portion of technical losses in power networks, yet robust field-based methodologies for evaluating efficiency improvements in real-world settings are lacking, particularly in sub-Saharan Africa. ", "purpose and objectives": "This article presents a novel randomised field trial (RFT) methodology designed to empirically quantify the efficiency gains and loss reduction achieved by deploying high-efficiency distribution transformers within an operational network. ", "methodology": "The RFT clusters substation feeders into matched pairs based on load profile and technical characteristics, then randomly assigns a high-efficiency transformer to one feeder within each pair. Core efficiency is measured using a precision three-wattmeter method under actual load conditions. The treatment effect on aggregate technical and commercial losses is estimated using a difference-in-differences model: \ Loss{it = \0 + \1 Treatmenti + \2 Postt + \3 (Treatmenti \ Postt) +, with inference based on cluster-robust standard errors. ", "findings": "As this is a methodology article, no empirical results from the trial are presented. The developed protocol successfully enrolled and randomised over 150 distribution transformers across multiple network regions. The primary anticipated outcome is a quantifiable reduction in median load losses, with the analysis powered to detect a relative reduction of 15% or greater at 80% power. ", "conclusion": "The proposed RFT framework provides a rigorous, evidence-based approach for evaluating grid efficiency interventions, moving beyond laboratory estimates to deliver actionable, field-verified performance data. ", "recommendations": "Utilities and regulators should adopt randomised field trial designs for capital-intensive grid equipment deployments to validate efficiency claims, inform procurement standards, and accurately forecast return on investment. ", "key words": "randomised field trial, distribution transformer, technical losses, difference-in-differences, energy efficiency, sub-Saharan Africa", "contribution statement": "This paper provides the first formalised RFT methodology for evaluating
Okello et al. (Mon,) studied this question.