<p>The solar air heater is widely used for low to medium-level heating by effectively harnessing solar energy. Its low thermal performance has always been a subject of study for researchers. Employing different geometrical disturbances to alter the flow regime for performance improvement is a common practice in this field. In the present study, spiral-shaped baffles with rotation have been investigated using the optimal geometrical roughness parameters (relative roughness height (e/H) = 0.8 and relative roughness pitch (P/e) = 8) for seasonal assessment. A comprehensive 4E analysis of the seasonal dynamics of a modified solar air heater highlights the enhanced thermal performance and seasonal adaptability of the system. Seasonal assessments reveal that summer irradiance is ~ 12% higher than in winter, improving operational efficiency. The modified system showed a 35.04% reduction in plate temperature during winter, while the reduction was ~ 21.1% in summer, emphasizing the impact of seasonal variations on thermal performance. Notably, useful heat gain increased by 21.15% in summer compared to 12.23% in winter, resulting in peak thermal efficiencies of 67.27% and ~ 56.1%, respectively. The summer season achieved a 32.5% higher thermohydraulic performance than winter. Exergy efficiency peaked at ~ 28.1% in summer and 24.72% in winter, indicating substantial gains over the conventional design. Sustainability Index values of 1.39 in summer and 1.33 in winter, along with reduced Improvement Potential values, reflect optimized performance. The exergoeconomic analysis showed superior exergoeconomic parameter values for the modified system over 10, 20, and 30&#xa0;years, underscoring its cost-effectiveness and long-term viability. Furthermore, the modified system achieved a 100% reduction in environmental impact after 20&#xa0;years and a 35% increase in CO₂ mitigation over 30&#xa0;years, earning carbon credits of $417.43 in summer and $308.57 in winter.</p>