System-Level Analysis of LED Retrofit Solutions for T8 Fluorescent Tubes: Harmonic Emissions, Photometric Impacts, and Compliance Considerations

This study investigates the harmonic emissions, photometric performance, and techno-economic implications of retrofitting T8 fluorescent tubes with LED alternatives under various ballast configurations. Experimental results reveal that while legacy fluorescent installations—whether magnetic or electronic—generally comply with EN IEC 61000-3-2 harmonic limits, most retrofit LED tube scenarios do not. The lack or ineffectiveness of power factor correction circuits in low-power LED tubes is identified as a key contributor to non-compliance. Moreover, the presence of magnetic ballasts introduces unpredictable effects: in some cases acting as harmonic filters, but in others exacerbating distortion, particularly when interacting with internal LED drivers. Photometric assessments further highlight inconsistent luminous output and flicker performance, especially when magnetic ballasts remain in place. Lighting simulations demonstrate that although ballast-based retrofits may yield tolerable illuminance levels, they consistently exceed ASHRAE 90.1 power density limits and may lead to overillumination when luminaires are retrofitted one by one without considering the photometric quantities, which are unknown when LED tubes are placed in an existing luminaire. Techno-economic analysis confirms that full luminaire replacement with appropriately selected LED systems—combined with design optimization—achieves higher energy efficiency, shorter return on investment, and reliable compliance. Furthermore, the study includes an assessment of colorimetric characteristics and metrics relevant to human-centric lighting, such as the melanopic daylight efficacy ratio (MDER) and equivalent melanopic daylight illuminance, revealing significant variations between fluorescent and LED retrofit solutions. These findings emphasize the importance of evaluating not only energy and photometric performance but also biological lighting impacts when considering retrofit strategies. The findings emphasize that lighting retrofitting should not be treated as a simple lamp replacement but as a system-level intervention. Properly engineered LED replacements provide a more consistent, efficient, and sustainable solution, supporting the objectives of long-term reliability, regulatory alignment, and Sustainable Development Goals 3, 7, 9, 11, and 12.