<p>Manufacturing SMEs play an important role in addressing the EU’s energy and climate challenges, as significant contributors both to economic output and greenhouse gas emissions. In Finland, these enterprises are vital for the national economy and sustainability goals but face significant barriers to energy optimization and Industry 4.0 adoption. Existing research often treats manufacturing SMEs as a homogeneous group, not addressing the diversity of barriers and drivers across micro, small, and medium-sized organizations across this sector. This paper, based on the <i>Enertelligence</i> -project conducted in Finland’s Ostrobothnia region—one of the country’s most industrialized areas—studies these differences through interviews with manufacturing SME managers, utilizing a maturity table to reveal variations in readiness and maturity across company sizes. The findings show that SMEs’ size significantly influences energy transition readiness, influenced by available resources, technological capabilities, and willingness to act. Additionally, external factors such as regulatory complexity and limited market incentives further hinder progress. The research introduces the innovation ecosystem approach as a regionally grounded theoretical framework to support manufacturing SMEs in overcoming these challenges. The insights have wider relevance for Finnish industrial policy and provide practical guidance for policymakers, stakeholders, and researchers seeking to accelerate sustainable modernization within the manufacturing SME sector.</p>