AccScience Publishing / AJWEP / Online First / DOI: 10.36922/AJWEP025310242
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ORIGINAL RESEARCH ARTICLE

Energy-efficient light-emitting diode retrofit and advanced control in municipal street lighting: A case study from Bulgaria

Plamen Tsankov1,2* ,  Milko Yovchev1,2 ,  Hristo Ibrishimov1,2
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1 Department of Electric Power Distribution and Equipment, Faculty of Electrical Engineering and Electronics, Technical University of Gabrovo, Gabrovo, Bulgaria
2 Laboratory Eco-friendly, Energy-saving, and Electromagnetically Compatible LED and Renewable Energy Components and Technologies, Center of Competence “Intelligent Mechatronics, Eco- and Energy-Saving Systems and Technologies,” Gabrovo, Bulgaria
AJWEP, 025310242 https://doi.org/10.36922/AJWEP025310242
Received: 1 August 2025 | Revised: 18 August 2025 | Accepted: 19 August 2025 | Published online: 11 September 2025
© 2025 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

Modernizing street lighting through light-emitting diode (LED) retrofits and advanced controls is recognized as an effective strategy for reducing energy use and costs. While numerous studies confirm these benefits in Western Europe, little is known about their performance in Eastern European municipalities. This study addresses this knowledge gap by presenting a case study of municipal street lighting in Bulgaria. It presents the methodology, implementation, and evaluation of an energy-efficient modernization project for municipal street lighting systems in the Bulgarian cities of Pavlikeni and Byala Cherkva. He project involved a complete transition from outdated lighting technologies (e.g., high-pressure sodium, compact fluorescent, and mercury vapor lamps) to high-efficiency LED luminaires, integrated with an intelligent control and monitoring system. An energy audit, conducted in accordance with national regulations and European standards (EN 13201), revealed that over 90% of luminaires had exceeded their operational lifespan and no longer complied with photometric and technical requirements. Lighting design classifications were applied in accordance with EN 13201:2016 to ensure compliance with the standard’s requirements for luminance, uniformity, and glare control. An optimization problem was defined and solved using specialized software to determine the lowest luminaire power, minimum pole height, and smallest bracket tilt angle, with fixed pole spacing, while maintaining regulatory compliance. Using DIALux evo, multi-scenario photometric simulations and optimizations were performed, resulting in 47 optimized lighting models tailored to specific street segments. The upgraded system incorporates adaptive dimming features, enabling nighttime power reduction through pre-programmed driver settings. A centralized cloud-based management system was implemented for remote monitoring and control, enhancing reliability and reducing maintenance. Post-implementation analysis demonstrated 79.5% energy savings (549,082 kWh/year), along with carbon dioxide emission reductions of 1,349 t/year and a financial payback period of 6.2 years. This case study highlights the technical, economic, and ecological viability of large-scale LED retrofit projects with smart controls, offering a replicable model for municipalities across Central and Eastern Europe seeking improved energy efficiency and reduced environmental impact.

Keywords
Light-emitting diode street lighting
Street lighting audit
Street lighting modeling and optimization
Energy efficiency
Smart lighting control
Carbon dioxide emission reduction
Public lighting retrofit
Funding
The design and implementation of the energy-efficient LED retrofit and advanced control project in the towns of Pavlikeni and Byala Cherkva are funded by the Municipality of Pavlikeni through the European Union’s National Recovery and Sustainability Plan for the Republic of Bulgaria.
Conflict of interest
The authors declare they have no competing interests.
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