ELEKTROTEHNIŠKI VESTNIK 79(3): 87-92, 2012 
ENGLISH EDITION 
Public lighting energy consumption in Slovenian municipalities 
from 2007 to 2011  
Mitja Prelovšek, Grega Bizjak, Matej Kobav 
Laboratory for Lighting and Photometry,University of Ljubljana, Faculty of Electrical Engineering,  Tržaška 25, 1000 Ljubljana, 
Slovenia   
E-mail: mitja.prelovsek@fe.uni-lj.si 
 
Abstract. The paper presents an overview of public lighting energy consumption of (road and urban lighting) in 
Slovenian municipalities between 2007 and 2011. It discusses significant improvements in the quality of public 
lighting resulting from the increasing awareness of the importance of public lighting and technological 
possibilities available on the lighting market. Three case studies of recent lighting renovations in Slovenian 
municipalities are analysed to enable assessment of energy consumption reduction one can expect from 
increasing efficiency of lighting installations. 
 
Keywords: public lighting, road lighting, municipalities, energy consumption 
 
 
 
1 INTRODUCTION 
Nowadays, public lighting is a commodity without 
which it would be difficult to imagine the contemporary 
world. It includes road lighting, lighting of pedestrian 
zones, façade and cultural heritage lighting as well as 
other public areas such as parking lots, underpasses and 
sports facilities. It doesn’t include lighting of private 
areas such as gardens, parking lots and similar. 
Public lighting can also be defined as lighting paid 
for by public institutions such as municipalities. The 
institutions managing the Slovenian state roads are 
DARS and Slovenian Road Agency, which is part of the 
Ministry for Infrastructure and Spatial Planning. 
However, the share of state-road lighting-energy 
consumption is relatively small compared to the energy 
consumed for lighting municipal roads. It is less than 10 
% [1]. 
Public lighting represents a relatively small 
proportion of the overall energy consumption in the 
country as it amounts to around 0.7 % [1]. The effort in 
reducing it, however, offers significant impact 
especially as public lighting is often the biggest public 
energy consumer in a municipality. Furthermore, 
investment in public lighting tends to have a quick 
payback time especially when the lighting equipment is 
rather obsolete. The payback time of a relatively new 
lighting installation, tends to be longer of course. This 
has made the pace of public lighting renovation to 
quicken markedly in the last couple of years in 
Slovenia. Moreover, the Lighting Pollution Decree 
(Decree of maximum values of light pollution (Uredba o 
mejnih vrednostih svetlobnega onesnaževanja; Official 
Gazette of RS no. 81/2007, modifications 109/2007 in 
62/2010) binds operators of lighting systems in the 
country to comply with various specifications imposed 
on performance characteristics of luminaires, lighting 
pollution, distribution and consumption. For municipal 
lighting the requirements most challenging to comply 
with are regarding lighting energy consumption and 
performance characteristics of the luminaires.  
At the Faculty of Electrical Engineering we have 
been following the development of public lighting for 
several years. In this paper we will present results of 
two studies in public lighting. One was conducted in 
2007 and the other in 2011. They both provide focused 
data on energy consumption. The 2007 study was made 
with the help of municipal financial departments and the 
2011 study was based on Lighting Plans adopted 
according to the Lighting Pollution Decree. As the 
Decree is such an important part of lighting industry in 
Slovenia, we will briefly present it in the following 
chapter. 
 
2 LIGHTING POLLUTION DECREE 
The Lighting Pollution Decree has enforced several 
changes in the field of lighting design, installation and 
maintenance. As to municipal lighting, the most far-
reaching requirement is the maximum allowed annual 
lighting-energy consumption. It is set at 44.5 kWh per 
inhabitant per year. The other and perhaps even more 
radical one, is the requirement of zero upward-light 
output ratio (ULOR). To comply with it, a large portion 
 
Received June 31, 2012 
Accepted October 4, 2012 

88     PRELOVŠEK, BIZJAK, KOBAV 
of road luminaires have to be removed from use and 
banned from the market. The exceptions concerning 
public lighting are: 
 When lighting the pedestrian zones in the 
vicinity of a cultural heritage object or 
building, luminaires that have ULOR of up to 
10 % may be used, provided that the power of 
the luminaire is less than 20W and that the 
illumination of the surface lit by the luminaire 
is less than 2 lux; 
 When the luminaire is part of a cultural 
heritage object itself, there is no ULOR 
limitation; 
 When lighting outdoor sport facilities (for 
example outdoor basketball court or soccer 
field) ULOR of up to 5% is allowed, but only 
until 10pm or 1 hour after the end of the event. 
 
The Decree of course includes several other 
requirements, the extent of which is, however, much too 
large for this article. 
   
3 PUBLIC-LIGHTING ENERGY CONSUMPTION 
IN SLOVENIAN MUNICIPALITIES 
In 2011 we started gathering the Lighting Plans of 
individual municipalities. Operators of lighting systems 
consuming more than 10 kW have to produce a Lighting 
Plan containing the following information:  
 Location of the lighting installation and 
detailed location of the light source; 
 Annual energy consumption, combined 
electrical power, number of installed 
luminaires and their ULOR; 
 The overall length and surface of lit roads and 
other public areas when the lighting installation 
is intended for road or public area lighting; 
 Surface area of the façade or cultural heritage 
building or object to be lit; 
 Advertising surface area and electrical power 
of all the light sources or luminaires used for 
advertising purposes.  
In our study we used Lighting Plans of municipalities 
who have already adopted them. There are some who 
still haven’t managed to draw them and while some do 
have similar documents, most of which don’t provide all 
the data required by the Decree. The most commonly 
missing data are those about the length of the lit roads, 
surface areas of lit cultural heritage buildings and 
surface areas of lit public areas. We gathered data about 
the number of installed luminaires, their combined 
electrical power and annual energy consumption from 
other documents as well in case the municipality didn’t 
produce the Lighting Plan yet. 
Data for 83 municipalities (40% of all the 
municipalities) were collected. In the 83 municipalities 
live 52% of all inhabitants of the country, while the 
surface area they cover is 42% of the overall country 
surface area. Only 50 had data about the length of their 
lit roads and knew the number of installed luminaires, 
total electric power consumed by their luminaires and 
annual energy consumption for public lighting. These 
data are represented in Table 3.1. 
Most of the municipalities produced their Lighting 
Plan in 2009 and 2011 as shown in Figure 3.1. 
 
 
Figure 3.1: Year of Lighting Plan procurement year. 
Based on the above data we calculated the average 
energy consumption per inhabitant (63.57 
kWh/inhabitant), average electric energy of the 
luminaire (153.86 W) and average energy consumption 
per lit kilometre of the road (27.834,9 kWh/km). 
Before obtaining the data, we assumed that public 
lighting of most of the municipalities that had adopted 
the Lighting Plan had been recently renovated, which 
could have, to a certain extent, distorted the data. 
However, it turned out that there is no significant 
correlation between the time the lighting was renovated 
and the existence of the Lighting Plan. Therefore we 
think the data obtained in this way can be applied to and 
averaged to the whole country. 
Table 3.1: Energy consumption for public lighting in 
Slovenian municipalities. 
 Average 
luminaire 
power  
[W] 
Consumption 
per inhabitant 
[kWh/inh] 
Consumption 
per lit km of 
the road 
[kWh/km] 
Cities  129.49 63.13 20,812.4 
Other 155.81 63.90 37,086.4 
Sum 153.86 63.57 27,834.9 
 
4 COMPARISON WITH THE 2007 DATA 
In 2007, we conducted a study similar to the one 
described above. The data provided by financial 
departments of the municipalities from paid electricity 
bills and power consumption. The data were consumed 
energy for public lighting and the number of 
inhabitants. After calculating the annual consumption 
per inhabitant [kWh/inh], the average annual consumed 
0
5
10
15
20
25
30
35
year 2008 or
earlier
year 2009 year 2010 year 2011

PUBLIC LIGHTING ENERGY CONSUMPTION IN SLOVENIAN MUNICIPALITIES FROM 2007 TO 2011 89  
energy per inhabitant for the whole country was 
calculated. This turned out to be 75,75 kWh per 
inhabitant. The average of the 11 urban municipalities, 
was a bit higher; 78.2 kWh per inhabitant. The average 
of the rest of municipalities was 73.8 kWh per 
inhabitant. 
It was seen that the energy consumption for public 
lighting had decreased from 75.75 kWh/inhabitant in 
2007 to 63.6 kWh/inhabitant in 2011, which is some 
16% reduction. 
 
 
Figure 4.1: Differences in energy consumption from 2007 
to 2011. 
Figure 4.1 shows the amount of saving that can be 
expected from the public-lighting renovations. Of 
course, the saving depends on the state of lighting 
installations before renovation. If the lighting 
technology used before renovation is relatively old 
(obsolete reflectors, inefficient light sources and 
degraded diffusers) saving will be bigger. 
In 2007 study we also analysed the power 
consumption for lighting the state-managed roads; it 
was 6.88 kWh/inhabitant. To sum up, the overall energy 
consumption in 2007 was 82.59 kWh/inhabitant. 
 
5 ENERGY CONSUMPTION REDUCTION 
POSSIBILITIES 
In the following chapter we will present three cases 
of public lighting renovations which will explain the 
extent of reductions in energy consumption that can be 
expected. 
5.1 Renovation in Celje municipality 
The Celje municipality with its 48.000 inhabitants is 
one of the biggest municipalities in Slovenia. Until 2008 
they renovated most of their public lighting 
infrastructure. According to the data by Elektrosignal, 
which manages most of the public lighting in the 
municipality, there were 4080 luminaires installed, 
which means one luminaire per every 12 inhabitants. 
Before the renovation the luminaires had mostly 400 W, 
250 W and 125 W light sources as shown on the Table 
5.1, where HPM denotes for metal-halide lamp and HPS 
denotes high pressure sodium lamp. 
Table 5.1: Light sources in Celje prior to renovation 
Light source 
  
Power [W] Number of 
light sources 
HPS or HPM 400 850 
HPS or HPM 250 620 
HPM 125 2610 
SUM  4080 
The overall electric power of all the light sources is 
821.25 kW. Combined with the losses in the ballasts, 
the electric power is some 862 kW. Based on the 
average of 4300 working hours per year of public 
lighting, the overall energy consumptions is 3.706.660 
kWh, which is 77 kWh/inhabitant. 
The renovation included all the luminaires, for 
which all the lamps were replaced by the more efficient 
high pressure sodium (HPS) lamps. The 400W HPM 
lamps were replaced by the 250W HPS lamps, 250W 
HPM lamps by 150W HPS lamps and 125W HPM 
lamps by the 36W fluorescent lamps. The number of 
light sources after the renovation is shown in Table 
3.1Tables 3.1 and 5.2. 
Table 5.2: Number of light sources after renovation (MH 
stands for Metal Halide) 
Light source 
  
Power [W] Number of 
light sources 
HPS 250 850 
HPS 150 620 
Fluorescent 36 1840 
MH 32 770 
SUM  4080 
As seen from the above data, the electric power of the 
light sources is 389.45 kW or 419 kW after adding the 
losses in the ballasts. At 4300 average working hours 
per year, the annual energy consumption is estimated at 
1.801.700 kWh or 37 kWh per inhabitant, which means 
the energy consumption dropped to 48% after the 
renovation. 
75,75 
 63,57  
78,20 
 63,13  
73,77 
 63,90  
0,00
10,00
20,00
30,00
40,00
50,00
60,00
70,00
80,00
90,00
2007 2011
All municipalities Urban municipalities Other municipalities

90     PRELOVŠEK, BIZJAK, KOBAV 
5.2 Estimation of energy-consumption saving in 
the Duplek municipality 
 The Duplek municipality lies in the eastern part of 
Slovenia and it has 6580 inhabitants, which means it is 
one of the minor Slovenian municipalities. In 2009, the 
municipality ordered a study of the development of 
public lighting [3]. The study analysed the available 
technology and estimated the potential savings gained 
by applying them.. Most of the light sources in the 
municipality at the time were 125W HPM.   
Table 5.3: Light sources in the Duplek municipality 
Light source Power 
[W] 
Number of 
sources 
Compact fluo 20 29 
MH 25 16 
Fluorescent 36 23 
MH 70 237 
HPM 125 547 
HPS 150 120 
HPS or HPM 250 31 
Based on the above data, the total power of all the light 
sources is estimated at 112.523 kW or, after calculating 
the power losses the ballasts at 121.534 kW. At 4300 
working hours, the annual energy consumption for 
public lighting is 522.594 kWh, which means 79.42 
kWh/inhabitant. 
The municipality estimated how much energy would 
be saved if all the mercury lamps were replaced by HPS 
ones. 
Table 5.4: Light sources after renovation 
Light 
source 
Power 
[W] 
Number of 
sources 
Fluorescent 18 23 
HPS 50 1 
HPS 70 828 
HPS 150 145 
HPS 250 6 
The total power of light sources after renovation would 
be 81.67 kW or 88.21 kW with the ballast losses 
accounted for. Annual energy consumption would be 
379.294 kWh, which means 57.64 kWh/inhabitant. The 
saving would be some 28% per year. 
Compared with the Celje municipality the relatively 
smaller savings are due to a larger proportion of HPS in 
the currently used light sources unlike is the case in 
Celje municipality. 
  
5.3 Estimation of energy consumption savings in 
the Mozirje municipality 
Having only some 4000 inhabitants, Mozirje is an 
example of a minor municipality. Until 2007 they had 
renovated most of their public lighting and in 2007 they 
analysed energy consumption to estimate the 
possibilities of further energy savings. At the time of 
our analysis there were 208 luminaires installed in the 
municipality. This is almost half of the national average, 
which is one luminaire per 10 inhabitants. Most of the 
luminaires in the municipality are fluorescent lamps. 
The number of HPS is small. This is due to the traffic 
traffic on most of the municipal roads, which is not very 
heavy. An overview of the types of the used lamps in 
Mozirje is presented inTable 5.5 
Table 5.5: Types of the used lamps in Mozirje municipality 
in 2007. 
Light source Power [W] Number of 
sources 
Compact fluo 23 88 
Compact fluo 36 80 
HPS 250 25 
HPS 400 10 
HPM 250 2 
HPM 400 3 
SUM                     208 
The total electric power of all the installed lamps is 16.8 
kW, which means 18.2 kW afteradding the ballast 
losses. At the 4300 average working hours this is 78.260 
kWh, or 19.74 kWh/inhabitant. The average energy 
consumption per inhabitant is here much less than the 
national average, because of the low number of installed 
luminaires in the municipality. 
To further decrease the energy consumption, the rest 
of the HPM lamps (5 luminaires) should be replaced 
with the HPS lamps. For example: 250 W HPM lamps 
should be replaced by 150 W HPS lamps and 400 W 
HPM lamps should be replaced by 250 W HPS lamps. 
Besides using more efficient lamps, a lighting control 
system, should be installed to further lower the light 
output and energy consumption during the time of less 
traffic. By doing so, the energy consumption would be 
decreased by some 10%, meaning the electric power 
would decrease from 18.2 kW to 17.6 kW. 
 
6 COMPARISON WITH THE STATE IN OTHER 
EUROPEAN COUNTRIES 
As part of our study, energy consumed by public 
lighting in Slovenia was compared with that consumed 
in some other European countries. The data for these 
countries were collected in 2007 [2] by Vito, Belgium, 

PUBLIC LIGHTING ENERGY CONSUMPTION IN SLOVENIAN MUNICIPALITIES FROM 2007 TO 2011 91  
for the European Commission. The reliability of the 
method used by Vito, which also analysed the Slovenian 
data, was lower than the one of the method we used 
both in 2007 and in 2011. It is for this reason that in our 
comparison we used the data we collected in 2007. 
We calculated two additional indicators of public 
lighting sustainability which are consumption per square 
kilometre of surface area and consumption per 
kilometre of the road. For the latter it must be stressed 
that the kilometre of the road means the whole length of 
the road and not just the lit part, which is the case at the 
lighting plans as specified by the light pollution Decree 
in Slovenia. 
 
Table 6.1: Indicators of public lighting sustainability for 
the compared European countries. 
Country 
  
Consumption 
per inhabitant 
[kWh/inh] 
Consumption 
per surface 
area 
[kWh/km
2
] 
Consumption 
per kilometre 
of road 
[kWh/km] 
Sweden 106,38 2.222,40 7.094 
Ireland 27,74 2.037,41 448 
Slovenia 82,59 8.147,42 4.229 
France 79,24 9.062,98 4.831 
Poland 62,83 7.675,46 6.246 
Germany 42,00 9.681,78 1.509 
The United 
Kingdom 39,81 10.163,79 5.926 
Belgium 90,55 32.625,79 6.584 
The 
Netherlands 46,00 18.166,93 5.947 
EU 25 51 5.987,30 3.565 
 
The most commonly used indicator in assessing about 
light pollution is the power consumption per inhabitant. 
However, this indicator has an inherent flaw, for not 
considering population density. Public lighting is 
designed based on the surface area and traffic 
parameters of the roads and other public surfaces. This 
means the cities and countries with a higher population 
density, for example Germany, the United Kingdom and 
the Netherlands, will tend to have lower consumption 
per inhabitant than sparsely populated ones [4]. 
This trend can be easily seen in Figure 6.1, where the 
only exceptions are Ireland and Belgium. The relatively 
higher power consumption rate per inhabitant in 
Belgium can be explained by the fact that they light a 
much higher proportion of their roads than other 
countries.  
 
 
Figure 6.1: Energy consumption per inhabitant for public 
lighting. Countries are ordered according to their population 
density. The trend of falling consumption per inhabitant with 
the increasing population is clearly visible. 
Consumption per surface area has a different kind of 
flaw; it prefers countries with large areas mostly devoid 
of people. Countries with a relatively even distribution 
of population density, such as France, Poland and the 
Netherlands, tend to perform worse than countries with 
large empty areas, such as Sweden and Finland. 
 
 
 
Figure 6.2: Annual energy consumption for public lighting 
per square km of surface area. Countries are ordered according 
to their surface area. 
Following the above, we are convinced that the best 
indicator of sustainability and efficiency of public 
 148,15  
 106,38  
 27,74  
 82,59  
 79,24  
 62,83  
 42,00  
 39,81  
 90,55  
 46,00  
Consumption per inhabitant 
[kWh/inh] 
Countries ordered by population density 
 8.147    
 32.626    
 18.167    
 2.037    
 10.164    
 7.675    
 2.364    
 9.682    
 2.222    
 9.063    
Consumption per sqm of surface area 
[kWh/km2] 
Countries ordered by surface area 

92     PRELOVŠEK, BIZJAK, KOBAV 
lighting is energy consumption per kilometre of roads. 
This indicator concerns road lighting, on which  
planning and designing of public lighting is based . It 
doesn't include lighting of squares, parks and other 
public surfaces, as their share in public lighting is 
relatively small. It should be noted that energy 
consumption per lit kilometre of roads is just 
informativeas it is almost impossible to obtain the data 
about the lengths of the roads that are lit. 
 
 
Figure 6.3: Energy consumption per kilometre of roads. 
 
7 CONCLUSION 
Public lighting in Slovenia has experienced extensive 
renovations which can be, to no small extent, attributed 
to the implementation of Lighting Pollution Decree, 
giving rise to a significant number of renovations in 
several Slovenian municipalities.  
As shown in the Chapter 5, the energy saving ranges 
from some 10% when renovating relatively modern 
lighting installations to some 50%, when renovating 
very obsolete and deteriorated lighting installations. 
Similarly, the investment payoff time is from 3 years to 
15 years respectively 
On the basis of these data a conclusion ca be drawn, 
that efficiency and sustainability of public lighting has 
been significantly improved. 
 
REFERENCES 
[1] G. Bizjak, M. B. Kobav, “Ocena možnosti za zmanjšanje porabe 
električne energije pri notranji in zunanji razsvetljavi”, 
Ljubljana, 2008. 
[2] P. Van Tichelen, T. Geerken, B. Jansen , M. Vanden Bosch 
(Laborelec),V. Van Hoof, L. Vanhooydonck (Kreios), A. 
Vercalsteren, “Final Report Lot 9: Public Street Lighting”, Study 
for the European Commission DGTREN unit D3, 2007. 
(EV_Ref) 
[3] J. Boček, D. Ferlin, P. Grobelnik, G. Ahtik, A. Borovnik, 
“Strategija razvoja javne razsvetljave v občini Duplek”, Velenje, 
2009. 
[4] Website: http://www.bestcountryreports.com/, June 2012. 
[5] Uredba o mejnih vrednostih svetlobnega onesnaženja okolja, 
Official Gazette of Slovenia, year 2007, edition: 81 
[6] Seminar: Lighting Technology, Grega Bizjak, Faculty of 
electrical engineering 
[7] Osram, Catalogue, Indoor and Outdoor Lighting, 2009/2010 
[8] Philips Luminaires Catalogue Europe, 2010 
[9] Study on possible savings of electrical energy for public lighting 
in Hrastnik Municipality, Faculty of electrical engineering, 2004 
[10] Website: http://www.celma.org, May 2012 
[11] Website: http://www.wikipedia.org, June 2012 
 
Mitja Prelovšek graduated in 2006 from the Faculty of 
Electrical Engineering, University of Ljubljana. He then 
enrolled to Royal Institute of Technology in Stockholm 
(Kungliga Tekniska Högskolan) on the Master's programme 
Architectural Lighting Design, which he completed with 
honors in 2008. Thereafter he worked as a lighting designer in 
Slovenia and Australia while continuning his research work 
for which he obtained the 2010 international award Young 
Lighter of the Year. Since 2011 he has been working as a 
researcher at the Faculty of Electrical Engineering ofLjubljana 
where his work areas include lighting pollution and road 
lighting. 
 
Grega Bizjak, is an Associated Professor and Head of the 
Laboratory of Lighting and Photometry at the Faculty of 
Electrical Engineering, University of Ljubljana. He is active in 
the field of lighting,photometry and electric power 
engineering. His main research interests are energy efficient 
indoor and outdoor lighting, use of daylight, LEDs in lighting 
applications and photometry. Prof. Bizjak is the president of 
the Slovenian National Committee of CIE and representative 
of Slovenia in the CIE Division 2. 
 
Matej B. Kobavis a teaching assistant at the Laboratory of 
Lighting and Photometry at the Faculty of Electrical 
Engineering, University of Ljubljana. He is active in the field 
of lighting and photometry and electric power engineering. 
His main research interests are lighting is use of daylight and 
energy efficient indoor and outdoor lighting and photometry. 
Herepresentative of Slovenia in the CIE Division 3. 
 4.229    
 7.692    
 5.947    
 7.094    
 6.584    
 448    
 6.246    
 5.926    
 4.831    
 1.509    
Energy consumption per length of roads 
[kWh/km] 
Countries ordered by length of roads