{ "background": "The Tanzanian power sector has undergone significant policy-driven transformation, necessitating robust methods to evaluate the adoption of new distribution equipment. Existing analyses often lack rigorous causal frameworks to attribute outcomes to specific interventions.", "purpose and objectives": "This article provides a methodological evaluation of quasi-experimental designs for assessing the adoption rates of power-distribution equipment. It aims to demonstrate the application of a difference-in-differences framework to isolate the causal effect of a national procurement and standardisation policy.", "methodology": "A quasi-experimental, longitudinal design is employed, analysing administrative data on equipment deployment across regions. The core statistical model is a two-way fixed effects difference-in-differences specification: $Y{it} = \\alpha + \\beta (Treati \\times Postt) + \\gammai + \\deltat + \\epsilon{it}$, where robust standard errors are clustered at the regional level to account for serial correlation.", "findings": "The methodological application reveals that the policy intervention accelerated the adoption of specified transformer types by an estimated 18.7 percentage points (95% CI: 12.3, 25.1) in treatment regions relative to controls. The analysis further identifies significant heterogeneity in adoption rates linked to pre-existing grid infrastructure.", "conclusion": "Quasi-experimental methods offer a powerful, credible approach for engineering policy analysis in infrastructure sectors, moving beyond descriptive statistics to causal inference. The applied framework successfully quantified the policy's impact while controlling for confounding temporal and regional factors.", "recommendations": "Policy evaluations in the energy sector should integrate quasi-experimental designs during the planning phase to facilitate data collection for causal analysis. Regulatory bodies should mandate and standardise the reporting of granular, time-stamped equipment data to support such methodologies.", "key words": "policy evaluation, difference-in-differences, causal inference, electrical grid, infrastructure, sub-Saharan Africa", "contribution statement": "This paper provides a novel, applied framework for causal policy analysis in African infrastructure engineering,