Energy efficiency programmes in South Africa's industrial parks aim to reduce energy consumption and associated costs for small businesses. A combination of quantitative surveys and qualitative interviews was employed to assess programme effectiveness. Small businesses in industrial parks saw an average annual cost reduction of £50,000 (95% CI: £42,000 - £58,000) after participating in the energy efficiency programmes. The mixed methods study confirmed that energy efficiency programmes led to significant cost reductions for small businesses in industrial parks over two years. Further research should explore scalability and long-term sustainability of these programmes within different sectors and regions. energy efficiency, cost reduction, revenue growth, industrial parks, South Africa The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.