# Efficiency Analysis of Roadway Lighting Replacement in a Selected Polish Municipality
## 1 Introduction  
Construction projects to improve the energy efficiency of street lighting systems are now a strategic element of economic, technological and social development. However, the decision-making process for selecting the optimal solutions to apply is very complex. An assessment of the economic efficiency of a building investment is becoming an essential element of all analyses performed prior to making a decision to construct. One reason is that certain investments, apart from economic savings, generate benefits for the environment, mainly ones that involve the modernization of how the demand for heat and electricity supplied to buildings is satisfied [1]. Several critical factors, such as difficulties in gaining access to credit by companies involved in the refurbishment of street lighting systems, budget constraints of municipalities,and unawareness of the actual energy and economic performance after a retrofitting intervention, require a decision-making approach that supports the municipal energy manager in selecting the optimal energy-efficient street lighting retrofit solution while looking not only at the available budget but also at the future savings in energy expenditures [2]. The authors [3] determined the actual energy savings when replacing high-pressure sodium (HPS) luminaires with light-emitting diode (LED) luminaires in street lighting by choosing an approach based on equal photopic or mesopic luminance levels. They considered the energy efficiency indicators of LED luminaires in both standard and reduced lighting regimes for different dimming scenarios. It was found that by using high-quality LED instead of high-quality HPS luminaires, energy savings can range from 31% to 60% when applying multi-stage dimming scenarios [3]. Similarly, another study [4] shows the benefits of LED technology and suggests that replacing traditional HPS luminaires with LED ones operated by a device with an integrated dynamic dimmer can save a significant amount of energy in the street lighting sector. The author demonstrated that the annual consumption of 2349.976 GWh with the use of HPS luminaires could be reduced by 47% to 1257.746 GWh per year. When a scenario with dynamic dimming is adopted, the energy consumed by street lighting can be reduced by up to 58% per year. Light-emitting diode (LED) technology is widely used in street lighting. However, its implementation requires a large investment, making it a costly affair. Thus, replacing sodium lamps with LED technology requires a comprehensive budget analysis [5]. A study conducted by [PERSON] et al. [5] aimed to calculate the probability of cost and energy reduction in the process of street lighting replacement with LED lighting. The authors analysed a 1470-metre-long road section with a total of 54 poles. According to the study, the initial investment is twice as high as traditional lighting, but adopting LED technology is more economical when considered over the long term. The cost of replacing the lamp is reduced by 51% over its lifetime. The use of LED technology in street lighting is, therefore, more efficient and has relatively lower running costs than traditional lighting. According to [6], significant savings can be achieved by not only replacing traditional luminaires with low-power LEDs but also by providing streetlights with smart light controllers and network connectivity, allowing the introduction of sensible light intensity management and reduction in maintenance costs. By replacing traditional street lighting with LED lamps, utilities can reduce energy and operating costs by 46% or more [6]. Significantly greater savings can be achieved by controlling the light intensity and even introducing streetlight networking with a function to detect actual conditions (e.g., human and car traffic, weather) by temporarily dimming the lights, which can lead to overall savings of up to 80% or more.