Energy and non-energy cost-benefit assessment of motor system optimization: A review and case study–based framework

Industrial and commercial motor-driven systems account for a large share of electricity consumption and represent a major opportunity for energy savings, cost reduction, and decarbonization. However, investment decisions for motor system optimization are often based mainly on direct electricity savings, while non-energy benefits such as reduced downtime, lower maintenance costs, improved reliability, higher productivity, enhanced safety, and reduced noise are frequently omitted or treated qualitatively. This study aims to develop a structured cost–benefit evaluation framework that integrates energy benefits and non-energy benefits to support motor system optimization and investment decisions. The methodology combines a literature review, case-study synthesis, classification of motor-system optimization technologies, development of a non-energy benefit monetization index, subsector–technology weighting factors, conservative scaling factors, and sensitivity analysis. The proposed framework is applied across industrial and commercial subsectors and technologies, including premium-efficiency motors, variable speed drives, synchronous reluctance motors, and permanent-magnet motor systems. The results show that motor system optimization can deliver electricity savings, commonly exceeding 30% in applications, particularly when system-level measures such as variable speed drives and improved controls are implemented. When non-energy benefits are included under conservative assumptions, total project benefits increase substantially and estimated payback periods be reduced on average by approximately 50%, considering a large variety of case-studies. The findings demonstrate that excluding non-energy benefits can significantly underestimate the economic attractiveness of motor system optimization. The proposed framework provides decision-makers with an approach for comparing technology options, adapting benefit weights to site-specific conditions, and prioritizing investments based on combined energy, operational, financial, and environmental benefits.