Smart metering as a driver for increasing energy efficiency in street lighting


By Maja Matejic and Bojan Lazarevic

The business case presented in this article represents a new approach in using smart metering to increase energy efficiency in the street lighting sector, and is the first of its kind and very unique in Serbia.

In 2007, a small Serbian municipality, Varvarin, was granted a local subsidy from the funds of the Deutsche Gesellschaft für Technische Zusammenarbeit GmbH (GTZ), as part of the contribution of the Federal Republic of Germany to the modernisation of the street lighting system. The municipality is located in Central Serbia with 20,000 inhabitants.

About the project
The project objectives are to decrease energy consumption in the street lighting sector by 10% over the next two years, provide electricity consumption monitoring in the sector in the local municipality, a public presentation of energy saving, greenhouse gas emission reductions, and other related aspects achieved through the implementation of energy efficiency measures in the street lighting sector and promotion of the importance of energy efficiency.

The project was conducted in association with four parties: GTZ, the company Minel Schreder, Varvarin municipality and the electricity distribution company Elektrosrbija.

Street lighting sector in Serbia
Modernisation of street lighting is a relatively simple energy efficiency measure with high energy saving potential and major improvement of quality of the municipal service. Street lighting electricity consumption represents 1.5% of the overall electricity consumption in Serbia. The electricity price for street lighting in Serbia is about 5 Euro cents/kWh. Even though the electricity price has increased by 22% in real terms since 2005, it is still much lower than in neighbouring countries.

Some facts and figures concerning municipal street lighting in Serbia are:

  • Poor management, obsolete equipment, lack of appropriate maintenance, subsidised electricity price, lack of metering
  • A high percentage of the installed lamps are often out of operation due to lack of maintenance
  • Electricity consumption is higher than necessary, as approximately 85% of light sources are mercury bulbs
  • Maintenance costs are higher than necessary and a burden for the municipal budget
  • Illegal connections to the street lighting system in some municipalities additionally reduce the revenues for municipal services.

Project implementation
Implementation of the project included the following activities:

  • Installation of new electricity meters in 17 substations
  • Establishment of a municipal monitoring unit for on-line tabular and graphical display of measured values and installation of user templates for data analysis. The central communication unit is equipping with the necessary hardware and software for data management covering measured and calculated data, such as: current electricity consumption, energy savings and budget savings, as well as reduced GHG emissions in the appropriate format
  • Installation and setting up of the software and user data acquisition interface
  • Installation of LED display, 2×1 m in size, located at a public place close to city hall for the public presentation of measured and calculated data related to the project (current electricity consumption, total electricity and GHG savings achieved from the moment of system installation and other benefits of the project)
  • Provision of a wireless GPRS-based communication between the meters, AMR control centre and municipal monitoring unit and between the municipal monitoring unit and LED display
  • Creation and organisation of the database on measured values and other relevant calculated values in the appropriate format
  • Installation of the software for communication between the municipal monitoring unit and LED display.

The system, with all its parts, is shown in Figure 1.

A Street lighting project system

Figure 1 – Street lighting project system

Meter requirements
The meters are the most important part of this project, which enables electricity consumption measurement and permanent collection for all relevant data which are necessary for system monitoring, various analyses and calculation of benefits.

Two types of meters are in use: Meters for active energy 3×230/400 V, 60 A, and accuracy class 2; and meters with accuracy class for active energy 1, reactive energy 3 and maximum demand 1, 3×230/400 V, 5 A connected over CT.

The meters are multifunctional, equipped with the appropriate number of tariff registers, with the possibility to keep all billing elements to a minimum 12 months.

The communication protocol for both local and external communication is IEC 62056-21 mod C.

Data monitoring
The system should be able to measure and to monitor following parameters:

  • Current line voltage (V) per line and per transformer unit
  • Current (A) per line and per transformer unit
  • Current active power (kW) per line and in total per transformer unit
  • Current reactive power (kVAr) per line and per transformer unit
  • Increment of electricity consumption (kWh) per line and in total per transformer unit
  • Frequency in the system (Hz) per transformer unit
  • Number, time and duration of power interruptions, if occurred.

Data reading and processing is managed by the municipal staff, every 12 hours.

Project visibility and data transparency
In order to enable visibility of the system operation, an on-line street lighting monitoring system was installed, including public presentation of the economic and environmental benefits achieved after modernisation of the street lighting system. The installation of this monitoring system with a public display makes this project unique (Figure 2).

A street light monitoring system

Figure 2 – Public display of street
light monitoring system

The monitoring system helps to improve system operation and allows prompt reaction on any disturbance or interruption in the system. Maintenance needs as well as illegal connections to the street lighting system can be identified immediately. The system can be further optimised by adjusting the light intensity through dimming or by reducing the number of lamps operating during the night hours. Permanent recording of the measured and calculated values enables municipal staff to perform all kinds of technical and financial analyses. Thus, indirectly, the monitoring system contributes both to energy savings and to improved quality of the municipal service. The results of such monitoring will be presented in public and on the internet through the web pages of the GTZ project and the Standing Conference of Towns and Municipalities (

Project benefits
Since Serbia has recently ratified the Kyoto protocol, greenhouse gas emissions have come into the focus of public interest, and a public display of emission reductions due to the implementation of particular energy efficiency measures effectively draws public attention to energy efficiency issues.

The estimated recovery time of the overall investment, through savings of about 35% in energy consumption and 30% in reduced maintenance costs, is between 7 and 8 years, based on the electricity price in 2007.

Benefits for the local municipality will be a decrease of energy consumption and electricity cost for street lighting.

The project also has enabled Elektrosrbija to gain new experience and knowledge in the use of smart metering, to understand the impact of smart metering on energy efficiency, and to change ways of conducting its business.

Families and private companies are continuously reminded, that energy and budget savings are possible, often more easily than has been assumed.

The interest of neighbouring municipalities shows that the project may have good potential for replication

Altogether through improved services in line with publicly visible energy savings and greenhouse gas emission reductions, local leaders and municipal energy managers may be able to campaign more successfully for a broader and more systematic approach towards municipal energy efficiency.