Poland as the EU Leader in Terms of Photovoltaic Market Growth Dynamics—Behind the Scenes

: The growing climate crisis forces the adoption of radical steps to neutralize our impact on the environment, despite the constantly growing demand for energy. Poland, which according to forecasts will not reach the EU target of 15% share of renewable energy sources by 2030, is nevertheless a leader in the EU in terms of the growth dynamics of the photovoltaic market. The aim of this article is to answer the question as to what caused such a huge interest in solar energy. In this article, the authors focus solely on residential installations. The dataset for the analysis was constructed on readily available national data on photovoltaics showing the key characteristics of the country and prosumers. According to this research, the prosumer’s proﬁle shows that home photovoltaics are most interesting for the poorest households in rural municipalities, in regions with the highest unemployment rate, and among citizens of pre-retirement age. The decision to invest in photovoltaics is also inﬂuenced by the availability of subsidies and the price level of energy bills. On the other hand, no impact was found on insolation and environmental pollution. The results of the study will allow for a more conscious shaping of energy policy at the EU, national and regional levels.


Introduction
Solar energy is widely recognized in the EU as crucial for creating a safe and sustainable energy system in the future. All future energy scenarios developed in the EU to meet the 2050 climate goals provide for a key role for solar energy. Over 90 companies and research institutions from 15 EU countries have initiated the Solar Europe Now campaign and signed its declaration. According to the signatories, solar energy is the key to achieving the climate neutrality goal by 2050. The initiative came from research centers, but with strong industry support it seeks to use the European Green Deal to reindustrialise and confirm the economic viability of large-scale PV production in the EU [1]. Solar PV currently covers 3% of total EU electricity demand, trending up to 15% in 2030. In several European countries, photovoltaics already cover more than 5% of annual electricity demand, and this target was initially only envisaged after 2020. It is worth noting that photovoltaic energy in the European Union showed strong growth in 2020, even though the COVID-19 pandemic has negatively affected the development of social and economic life in many aspects [2].
In Poland, almost 70% of electricity is generated from coal, which results in high greenhouse gas emissions. A side effect of such a structure of energy sources is the price of electricity in Poland-the highest in the European Union [3]. The current objectives of the EU regarding the level of RES in the energy mix are already a huge challenge for Poland. At the same time, the EU's ambitions in this area are growing: the ministers of energy and environment from six EU countries called for a 100% renewable energy scenario to be included in long-term forecasts for 2050, especially 100% in the electricity sector [4].
On the other hand, in recent years Poland has become the European leader in terms of the dynamics of the photovoltaic market growth. 2020 was the best year in the history of photovoltaics in Poland, and the current data for 2021 confirm that this trend is gaining momentum. However, photovoltaic technology has been present on the Polish market for years [5]. In that case, what caused such a dynamic increase in investments in the field of photovoltaics? In particular, what prompted individual buyers to invest in solar energy? The aim of this study is to define the drivers of investment in renewable energy sources by individual consumers (prosumers), thus answering the following questions: (1) What is the impetus for such a sudden shift towards solar energy? (2) Which regions/voivodeships in Poland have the greatest potential and do they use it? (3) What is going on behind the scenes when individual buyers decide to buy solar PV installations?
The answer to these questions is crucial for the further development of renewable energy sources, in particular solar energy, and can serve as a basis for a more conscious shaping of energy policy at the EU, national and regional levels. Of course, we can draw on solutions used in Germany, Spain, or the UK-both in terms of policies and specific tools, but as the examples of these countries show, success is always the result of both the solutions used and the specificity of the country (including political, legal, economic, socio-cultural, and technological factors) [6]. Failure to adapt legal and financial solutions may weaken or inhibit the development of investments in RES and, consequently, failure to achieve the objectives in this area, both at the level of individual countries, including Poland, and the entire EU.
In this article, the authors focus solely on residential installations (interchangeably described as prosumer, consumer, end-user, home, domestic sector, residential sector, and the household). It does not take into account voltaic farms and industrial installations. The dataset for the analysis was constructed on readily available national data on photovoltaics showing the key characteristics (such as infrastructure, localization, and individual investors).
In the remainder of the work, we will present the background to the development of photovoltaics as a green energy source in the world, in the EU, and in Poland. In the Methods section, we will present the methodological assumptions of the research, and then in the Results section, we will discuss the most important findings of the research. The paper will end with conclusions and an indication of limitations and further research directions.

Climate Crisis and Solar Energy
The fast-paced global economy continues to experience increased energy demandrecent forecasts show that this trend will continue with an average increase of 1.2% until 2040 [7]. This increase is also associated with an increase in the population and the desire to continuously improve the standard of living [8]. This model of economic growth, used for many years, has resulted and continues to result in overexploitation of natural resources and environmental degradation, as energy has so far been obtained mainly from conventional sources such as coal, gas, and oil. This forward-looking trend is leading to a number of environmental problems, the most prominent of which are greenhouse gas (GHG) emissions and climate change.
The awareness that the world's traditional energy resources are limited [9][10][11], and that the use of fossil fuels in energy production has a negative impact not only on the environment but also on human life and health has made it necessary to search for new ecological energy sources and has increased interest in renewable energy sources (RESs). Both social pressure and international action are forcing changes in the structure of energy sources. Currently, many countries, especially in the EU, are taking measures to ensure environmental protection and more sustainable development, with reference to the environmental Kuznets curve [12].
The economic development of the world depends on access to cheap energy sources, and renewable energy sources can provide this access. In 2019, renewable energy sources already accounted for as much as 34% of gross electricity consumption in the EU-27, and the target for 2030 is 40%. Although two-thirds of the total electricity produced from renewable sources is accounted for by wind and hydropower (35% each), solar energy is the fastest growing RES: in 2008 it was only 1% and in 2019 it had already reached 13% [13]. From the point of view of technology and finance, solar energy is also considered a promising renewable energy source for the housing sector, which, according to the World Resources Institute, is the second main source of energy-related emissions (11.4% of total emissions), just after road transport (12.5% of total emissions) [14].
In an effort to counteract the negative effects of globalization, and at the same time to ensure the conditions for further sustainable development, countries around the world are taking various actions to reduce greenhouse gas emissions while ensuring the conditions for the competitiveness and innovation of economies in the global market. The United Nations (UN) has been the initiator of such activities for many years. At the annual climate summits, it always calls for faster and more decisive action to protect the environment. The Intergovernmental Panel on Climate Change (IPCC) in its latest report, "Climate Change 2021: the Physical Science Basis" [15], emphasizes that the remedy for climate change is determined and ambitious action to reduce emissions of carbon dioxide and other greenhouse gases is needed. The European Union (EU) is not deaf to these calls and is an increasingly active and ambitious participant in this process. At the last UN climate summit (COP25) in December 2019 in Madrid, Spain, the European Commission presented a new European climate strategy called the European Green Deal [16]. The strategy assumes that by 2050 the EU economy should become a zero-emission, climateneutral economy [17,18]. This is related to, inter alia, a significant increase in the share of RESs in the energy mix of EU countries. In terms of climate protection, this strategy is the farthest from the commitments made under the Kyoto Protocol [19], which should be considered the most important factor stimulating the development of renewable energy both in the world and in the EU.
The policy of the European Union in the field of renewable energy is unambiguousthe European economy is to strive to reduce carbon dioxide emissions, which is evidently related to the development of renewable energy sources [20,21]. Efficient use of energy, as well as human, economic and natural resources, is a basic principle of sustainable energy development (SED) [22]. The Climate and Energy Policy contains common EU assumptions and goals for the years 2021-2030. From the perspective of 2030, the most important of them include [23,24]: • Reduction of at least 40% of greenhouse gas emissions (compared to 1990 levels) • Increase in the share of energy from renewable sources in total energy consumption to a minimum of 32% • Increase in energy efficiency by at least 32.5%.
The Green Deal initiative also includes measures to ensure better resource efficiency through the transition to a clean circular economy and the reduction of pollution levels. These goals are to be achieved through actions that include investments in the latest environmentally friendly technologies. As an EU member state, Poland is also obliged to implement a number of regulations regarding actions undertaken within the framework of the European common energy policy, contained mainly in the document "Poland's energy policy until 2030" [25].
Among the various renewable energy sources available, the most attention is paid to solar energy as it is considered carbon neutral and can be used to cover both electricity and heating and cooling needs [26,27]. The amount of solar energy reaching the Earth annually exceeds global demand many times over [28,29], but due to the fact that it is distributed energy, it is difficult in practice to exploit it well.
According to the definition provided by International Renewable Energy Agency (IRENA): "Photovoltaics (PV), also called solar cells, are electronic devices that convert sunlight directly into electricity" [30]. The modern solar cell is likely an image most people would recognize-they are in the panels installed on houses and in calculators. They were invented in 1954 at Bell Telephone Laboratories in the United States. Today, PV is one of the fastest-growing renewable energy technologies, and is ready to play a major role in the future global electricity generation mix [30].
The main barriers to the use of photovoltaics as an energy source are economic factors (the high price of photovoltaic installations and the cost of energy accumulation when not directly used), high dependence on location (seasonal and daily differences in the amount of energy produced, dependence on the amount of light and the occurrence of shading), technical aspects (such as decrease in panel performance due to life cycle), as well as safety and legal aspects [31,32]. Despite the difficulties observed, the global production of photovoltaic energy in recent years has dynamically increased from 32 TWh in 2010 to 544 TWh in 2018, with the largest producers being China (31.9% of the global total), the USA (14.7%), Japan (11.3%) and Germany (8.3%) [33].
This has encouraged researchers to explore the characteristics of consumers choosing photovoltaic installations from the perspective of, for example, the type, size, and location of their property, or their income, education, and family size [34][35][36]. Numerous studies have also been devoted to factors influencing consumer decision-making regarding solar panels [37][38][39]. However, these decisions are largely dependent on the regional energy infrastructure and location (in terms of insolation), as well as the existence and nature of PV support investment support programs. As the results of the above-mentioned studies show, the decision to invest in individual photovoltaic installations is highly related to geography and economy. Therefore, research results are difficult to compare internationally, and research is mainly focused on specific countries and regions [26,29,31].
As already mentioned, the EU assumes that the share of renewable energy in 2030 will reach a level of 32%. To achieve this goal, it is necessary to increase the use of renewable energy in the energy sector to at least 65%, with a solar energy share of 440 TWh/year [40]. Part of this goal may be realized by the roof installations of energy consumers. It is estimated that almost 25% of the EU's current electricity consumption can be produced by rooftop systems. However, this requires systemic support at the national and EU level, aimed at stimulating greater involvement of citizens in achieving the EU transition to a low-carbon energy system [41]. Depending on the cost of living in each country, the initial cost can be difficult to pay without a financing system, especially in Eastern European countries. Overall, the simple payback period of the scheme is less than 11 years, in most cases subsidy-free [27,42].

Photovoltaics in Poland
In Poland, 67.9% of the generated electric energy is produced from coal (Figure 1), which results in high emissions of greenhouse gases [43].As a result of such a production structure, the price of electric energy in Poland is the highest in the European Union [44]. The energy policy of Poland to date has not fit in with the global trends favoring the transition to energy systems based on RESs [45]. After several years of dynamic development of wind energy, the increase in the capacity of installed wind turbines has been abruptly hampered by unfavorable energy policy regulations [46] and a significant drop in the prices of green certificates [47]. Hydropower is also experiencing hard times: in 1935 there were 8000 water installations, while now this number has dropped to 761 units (with a total capacity of 994 MW) [48]. Until 2019, the solar energy market in Poland (especially photovoltaics) was developing at a relatively slow pace, and at the end of May 2019, installed capacity did not exceed 300 MWp [49]. In 2020, the total installed electric capacity of all RES installations in Poland exceeded 9500 MW. However, the distribution of these installations is not very differentiated regionally. The highest capacity is produced by the Zachodniopomorskie voivodeship (1800 MW), and the smallest by the Małopolskie voivodeship (150 MW) [50].
According to current predictions, Poland will not manage to meet the European Union requirement [51] concerning share of RES in gross final energy consumption. However, nowadays dynamic growth in the photovoltaic market can be observed. In 2019, a substantial increment of new PV installations took place. 2020 was a record year in the history of photovoltaics in Poland. Preliminary data for the year 2021 also prove that this trend has become very much stronger [42], as shown in Figure 2. Until 2019, the solar energy market in Poland (especially photovoltaics) was developing at a relatively slow pace, and at the end of May 2019, installed capacity did not exceed 300 MWp [49]. In 2020, the total installed electric capacity of all RES installations in Poland exceeded 9500 MW. However, the distribution of these installations is not very differentiated regionally. The highest capacity is produced by the Zachodniopomorskie voivodeship (1800 MW), and the smallest by the Małopolskie voivodeship (150 MW) [50].
According to current predictions, Poland will not manage to meet the European Union requirement [51] concerning share of RES in gross final energy consumption. However, nowadays dynamic growth in the photovoltaic market can be observed. In 2019, a substantial increment of new PV installations took place. 2020 was a record year in the history of photovoltaics in Poland. Preliminary data for the year 2021 also prove that this trend has become very much stronger [42], as shown in Figure 2. Until 2019, the solar energy market in Poland (especially photovoltaics) was developing at a relatively slow pace, and at the end of May 2019, installed capacity did not exceed 300 MWp [49]. In 2020, the total installed electric capacity of all RES installations in Poland exceeded 9500 MW. However, the distribution of these installations is not very differentiated regionally. The highest capacity is produced by the Zachodniopomorskie voivodeship (1800 MW), and the smallest by the Małopolskie voivodeship (150 MW) [50].
According to current predictions, Poland will not manage to meet the European Union requirement [51] concerning share of RES in gross final energy consumption. However, nowadays dynamic growth in the photovoltaic market can be observed. In 2019, a substantial increment of new PV installations took place. 2020 was a record year in the history of photovoltaics in Poland. Preliminary data for the year 2021 also prove that this trend has become very much stronger [42], as shown in Figure 2. In 2020 alone, 2635 megawatts (MW) of solar energy were installed in Poland-three times more than in 2019 (823 MW). According to the European association of the photovoltaic industry Solar Power Europe, the Polish photovoltaic market is expected to grow by 35% annually, and in 2024 the total photovoltaic capacity is to reach 8.3 GW. According to the Polish Photovoltaic Society (PV Polska), the number of registered smallscale systems (less than 50 kW) with an average power of 6.5 kilowatts increased from 155,000 (992 MW) at the end of 2019 to 457,400 (3 GW) at the end 2020. These small-scale prosumer micro-installations systems are responsible for over 75% of the total installed PV capacity in Poland. Already over half a million users of micro-installations are behind such an impressive increase in installed capacity [52].
This phenomenon is confirmed by other studies as well. At the end of 2020, Poland was in the first place in the European Union in terms of the growth rate of photovoltaic power calculated on the basis of the cumulative compound annual growth rate (CARG) [53]. According to the Report of the Institute of Renewable Energy for Poland, the cumulative (combined) growth rate in 2016-2020 amounted to 114%, compared with the EU average of 10.3%. Therefore, Poland is the European leader in terms of the growth dynamics of the photovoltaics (PV) market and in 2020 Poland approached the world's top 10 countries in terms of power growth (13th place) [54]. According to Solar Power Europe, in 2020, Poland (2463 MW) was in 4th place in terms of increasing the installed PV capacity in the European Union. Only Germany (4736 MW), the Netherlands (3036 MW) and Spain (2812 MW) were ahead of Poland [55]. As reported by Polskie Sieci Elektroenergetyczne (Polish Power Grid), on 1 December 2020, the installed capacity in photovoltaics was 3.7 GW. Compared to 1 December 2019, this means an increase of 182% [56].
Although Poland has become the European leader in terms of the dynamics of the photovoltaic market growth only in recent years, photovoltaic technology has been present on the Polish market for years. The data in Figure 3 reflects the solar photovoltaic capacity installed and connected in Poland in the last century [57]. photovoltaic industry Solar Power Europe, the Polish photovoltaic market is expected to grow by 35% annually, and in 2024 the total photovoltaic capacity is to reach 8.3 GW. According to the Polish Photovoltaic Society (PV Polska), the number of registered smallscale systems (less than 50 kW) with an average power of 6.5 kilowatts increased from 155,000 (992 MW) at the end of 2019 to 457,400 (3 GW) at the end 2020. These small-scale prosumer micro-installations systems are responsible for over 75% of the total installed PV capacity in Poland. Already over half a million users of micro-installations are behind such an impressive increase in installed capacity [52]. This phenomenon is confirmed by other studies as well. At the end of 2020, Poland was in the first place in the European Union in terms of the growth rate of photovoltaic power calculated on the basis of the cumulative compound annual growth rate (CARG) [53]. According to the Report of the Institute of Renewable Energy for Poland, the cumulative (combined) growth rate in 2016-2020 amounted to 114%, compared with the EU average of 10.3%. Therefore, Poland is the European leader in terms of the growth dynamics of the photovoltaics (PV) market and in 2020 Poland approached the world's top 10 countries in terms of power growth (13th place) [54]. According to Solar Power Europe, in 2020, Poland (2463 MW) was in 4th place in terms of increasing the installed PV capacity in the European Union. Only Germany (4736 MW), the Netherlands (3036 MW) and Spain (2812 MW) were ahead of Poland [55]. As reported by Polskie Sieci Elektroenergetyczne (Polish Power Grid), on 1 December 2020, the installed capacity in photovoltaics was 3.7 GW. Compared to 1 December 2019, this means an increase of 182% [56].
Although Poland has become the European leader in terms of the dynamics of the photovoltaic market growth only in recent years, photovoltaic technology has been present on the Polish market for years. The data in Figure 3 reflects the solar photovoltaic capacity installed and connected in Poland in the last century [57]. So where is the current boom in the photovoltaic market in Poland coming from? From reports prepared by governmental and non-governmental institutions, we learn that the reasons for this state of affairs comprise the following 4 factors.
(1) The members of the European Union are obliged to ensure a specific share of energy from renewable sources in the final gross energy consumption. The legal basis for Poland's obligations regarding the share of energy from renewable energy sources is Renewable Energy Directive II of 2018 [58] on the promotion of the use of energy from renewable sources. As a result of the European climate policy, the draft of the Polish Energy Policy to 2040 had to be focused on renewable sources. According to So where is the current boom in the photovoltaic market in Poland coming from? From reports prepared by governmental and non-governmental institutions, we learn that the reasons for this state of affairs comprise the following 4 factors.
(1) The members of the European Union are obliged to ensure a specific share of energy from renewable sources in the final gross energy consumption. The legal basis for Poland's obligations regarding the share of energy from renewable energy sources  [62]. Considering the high prices of electricity and the forecast continuous increase in energy prices, in particular for the consumer sector on the most expensive C tariff, this is a very attractive investment market. According to the Central Statistical Office, in 2020 the electricity bills of households increased by 11.7% year to year [63].
Numerous studies of this phenomenon also show that climatic conditions [64,65] and growing environmental awareness [66,67], as well as innovative and increasingly effective technologies, are also important [50,68,69].

Materials and Methods
The research was conducted in Poland, at the voivodeship level. The data was obtained from a variety of publicly available sources, including international organizations such as the International Renewable Energy Agency (IRENA), an intergovernmental organization that supports countries in the transition to sustainable energy, official sources of European (Eurostat) and national statistical data (Polish Statistics, Energy Market Agency), as well as reports from industry associations (including the Institute for Renewable Energy).
In the first step, the authors checked what percentage of households received subsidies for solar installations in individual provinces (Figure 4). In the next step, a model was created that would allow a check of what influenced the fact that home photovoltaics were so eagerly installed in the Podkarpackie, Małopolskie,Świętokrzyskie, Opolskie, and Wielkopolskie provinces. The authors created a database consisting of 35 variables. Because they were ch terized by various measures, including PM10 concentration, connected load, km 2 , P zloty and other measures, all data in the database were normalized to create a correla matrix.
To make the test results easier to visualize and interpret, not one correlation m was created, but three-according to the modules described above. Annexes A, B an contain successively the variables characterizing the technological infrastructure, the climatic and environmental conditions and the consumer profile-in all cases, br down by voivodeships. The input data (Appendixes A-C) for all calculations were pared using a Microsoft Excel spreadsheet. Correlation matrices with correlation co cients were generated using the additional Excel Analysis ToolPak program. Correla coefficient is standardized measure, which ranges from −1 to 1, where "0" means com The model is composed of three modules representing consumer profile, location, and infrastructure. In the construction of the model at the voivodeship level, the following variables were considered: (1) Infrastructure: The authors created a database consisting of 35 variables. Because they were characterized by various measures, including PM 10 concentration, connected load, km 2 , Polish zloty and other measures, all data in the database were normalized to create a correlation matrix.
To make the test results easier to visualize and interpret, not one correlation matrix was created, but three-according to the modules described above. Annexes A, B and C contain successively the variables characterizing the technological infrastructure, then the climatic and environmental conditions and the consumer profile-in all cases, broken down by voivodeships. The input data (Appendices A-C) for all calculations were prepared using a Microsoft Excel spreadsheet. Correlation matrices with correlation coefficients were generated using the additional Excel Analysis ToolPak program. Correlation coefficient is standardized measure, which ranges from −1 to 1, where "0" means complete independence of data. In order not to duplicate data we removed half of the table, and then we have a triangular matrix (see Tables 1-3). The matrix allows us to quickly see the relationships that exist between the phenomena studied. Interpretation of the results can be found in the Results section.

Results
(1) Are they people with higher education?
(3) Are they the inhabitants of the most polluted regions in Poland? (4) Are they low-income citizens from areas with high unemployment rates or lowincome retirees and pensioners who are terrified by rising electricity prices? (5) Are they owners of the farms that consume the most electricity? (6) Are they inhabitants of areas with the highest number of sunny hours a year use this potential?

Infrastructure
As presented in Appendix A, the largest number of subsidies was granted in southern Poland (Podkarpackie, Małopolskie,Świętokrzyskie, Opolskie voivodeships) and western Poland (Wielkopolskie voivodeship). These voivodeships are agricultural and forested areas. 50% to 68% of these areas are rural municipalities. Additionally, between 26% and 38% of the area of these voivodeships is covered by forests. According to the data of the Central Statistical Office, these are low-income voivodeships.
The Podkarpackie voivodeship had the largest allocation for the photovoltaic cofinancing programs. The greatest connection potential is in the Wielkopolskie voivodeshipthis voivodeship stands out significantly from the others in this respect. The smallest opportunities are offered by the Podkarpackie,Świętokrzyskie and Opolskie voivodeships.
The range of the level of dependence of variables for data from the Infrastructure correlation matrix (Table 1) shows that there is a strong relationship (correlation coefficient = 0.79) between the percentage of households that received subsidies and the amount of allocation for programs in individual provinces. In other words, the more voivodeships allocated to subsidies for photovoltaics, the more households benefited from it. Moreover, the more households spent on electricity, the more willingly they applied for a subsidy (correlation coefficient = 0.68).

Location
As presented in Appendix B covering the location data, the best values of solar radiation intensity are in the Opolskie voivodeships. The greatest environmental pollution is in the Małopolskie voivodeships. Surprisingly, the range of the level of dependence of variables for data from the location correlation matrix (Table 2) shows that the polluted environment (average annual concentration of PM 10 ) is not a motive at all to invest in renewable energy sources (correlation coefficient = −0.06). Interestingly, voivodeships in Poland that have the sunniest hours per year do not use this potential and are the least interested in solar energy (correlation coefficient = −0.84).

Consumer Profile
As presented in Appendix C with the consumer profile per voivodeships data, the highest percentage of households that received subsidies for photovoltaic installations are the Podkarpackie, Małopolskie,Świętokrzyskie, Opolskie, and Wielkopolskie voivodeships. At the same time, Podkarpackie,Świętokrzyskie, Opolskie, and Wielkopolskie voivodeships comprise one of the poorest regions, with an average monthly salary of over PLN 330 less than in other regions of the country. Additionally, Podkarpacie and Swiętokrzyskie have one of the largest numbers of unemployed.
The range of the variable dependency level for the data from the consumer profile correlation matrix (Table 3) shows that home photovoltaics are of most interest in the poorest households, where the unemployment rate is the highest (correlation coefficient = 0.47), among inhabitants of rural municipalities (correlation coefficient = 0.31), and in those of pre-retirement age (correlation coefficient = 0.89).

Discussion and Conclusions
The growing climate crisis, confirmed by numerous studies, forces us to take radical steps to neutralize the impact of the economy on the natural environment. On the other hand, in the coming decades in the European Union and globally, we will see a continuous increase in energy consumption. Consequently, all future energy scenarios developed in the EU to meet the 2050 climate goals highlight the crucial role of solar energy, widely recognized as key to creating a secure and sustainable energy system of the future. Unfortunately, according to current forecasts, Poland will not be able to meet the European Union requirement regarding the share of renewable energy sources in gross final energy consumption. With almost 70% share of electricity generated from coal, the price of electricity in Poland is also the highest in the European Union.
At the same time, at the end of 2020, Poland was in the first place in the European Union in terms of the growth of photovoltaic power calculated on the basis of the cumulative annual growth rate CAGR. The aim of this study was therefore to answer the following questions.
(1) What is the impetus for such a sudden shift towards solar energy? (2) Which regions/voivodeships in Poland have the greatest potential and do they use it? (3) What is going on behind the scenes when individual buyers decide to buy solar PV installations?
The study was limited to Poland for two reasons. First of all, only in Poland was there such a dynamic growth of individual investments in photovoltaic installations with very weak investments in other renewable energy sources. Secondly, as shown by previous studies, the phenomenon of individual investments in renewable energy sources is usually concentrated in individual countries or regions due to the multi-factor decision-making process.
Despite the difficulties in researching this phenomenon, this problem is very important, because the housing sector accounted for over 10% of total greenhouse gas emissions in EU [14]. At the same time, almost 25% of the EU's current electricity consumption can be produced by rooftop systems [27] and only in Poland have individual PV investments reached the level of over 75% of the total installed capacity. Thus, this study was limited to individual investors-prosumers. The dataset for the analysis was constructed on readily available national data on photovoltaics showing the key characteristics (such as infrastructure, localization, and individual investors).
Summarizing the research results, it was noticed that, surprisingly, as presented in the Photovoltaics in Poland section, the sudden and rapid increase in interest in individual investments in photovoltaics was not caused by climatic conditions [64,65] and the growing concern for the natural environment [66,67], but by numerous and very beneficial programs for individual recipients of co-financing investments in photovoltaic installations and favorable settlements regarding the surplus of solar energy produced [60]. An additional stimulus on the part of consumers concerned increasing energy prices-in Poland in 2020 alone electricity prices for individual consumers increased by over 10% [63]-as well as innovative and more and more effective technologies [50,[68][69][70].
Based on the analysis of the data presented in the Results-Location subsection, the regions with the best solar radiation intensity values, and thus with the potential for investments in solar energy, are the Opolskie, Lubuskie orŚląskie voivodships. The greatest environmental pollution (and thus demand for green energy) occurs in the Małopolskie, Sląskie or Dolnośląskie voivodships.
As emphasized in the section Results-Infrastructure, the highest connection potential is in the Wielkopolskie voivodship. This voivodship stands out significantly from other voivodships in this respect. The lowest available connection capacity [MW] is offered by the Podkarpackie,Świętokrzyskie and Opolskie voivodships. And it is in the Podkarpackie voivodship that we have the highest percentage of households that received subsidies for photovoltaic installations [2.42%].
On the basis of the results presented in the subsection Results-Consumer profile, it can be concluded that the highest percentage of households that received subsidies for photovoltaic installations are found in the Podkarpackie, Małopolskie,Świętokrzyskie, Opolskie and Wielkopolskie voivodships. At the same time, the Podkarpackie,Świętokrzyskie, Opolskie and Wielkopolskie provinces are among the poorest, with an average monthly salary of over PLN 330 lower than in other regions of the country. Additionally, Podkarpacie andŚwiętokrzyskie have one of the highest levels of unemployed. In other words, investment is dominant in poor regions for which rising energy prices (the highest in the EU) are a significant expenditure due to low wages or pensions. Numerous and favorable programs for co-financing photovoltaics in Poland also played a huge role. The standard period of return on investment is 11 years, but with an additional payment of up to 50%, this period can be significantly shortened.
To sum up, the driving forces behind investments in renewable energy sources by individual consumers (prosumers) are subsidies (correlation coefficient = 0.79), the cost of household energy (correlation coefficient = 0.68) as well as location-investments in photovoltaics are more popular in rural households (correlation coefficient = 0.31), age, and more precisely, pre-retirement age (correlation coefficient = 0.89) and economic situationhousehold solar farms are the most interesting in the poorest households, in the regions where the unemployment rate is the highest (correlation coefficient = 0.47). On the other hand, factors such as pollution and solar radiation intensity are not drivers of solar energy production. For the annual mean concentration of PM 10 , the correlation coefficient is = −0.06, and for the total number of sunny hours per year, the correlation coefficient is = −0.84.
The above research results can be used in the process of shaping EU, national and regional RES policies. First, the research results once again confirm that financial support for photovoltaic micro-installations can be considered a very effective policy. As mentioned in the article, this stimulates greater citizen involvement in the EU's transition to a low carbon energy system [41], although upfront costs represent major barriers, especially in Eastern European countries [27].
However, the bad design of the program may lead to paradoxes such as in Poland, where the regions with the highest photovoltaic profitability in terms of the level of insolation are not investment leaders in this area. Most of the investments are located in regions where the number of sunny days/hours is much smaller. A similar situation occurs in places with polluted air. It is not the people of the most polluted regions that invest in solar energy, but those with relatively good air quality. Moreover, in a situation where the poorest inhabitants of a region or country will invest in photovoltaic programs as a result of support programs, the price factor will be decisive, and thus the cheapest and the least technologically advanced installations will be selected, and consequently the potential of this energy source will not be fully used.
However, this study has some limitations. Firstly, the data are analyzed at the voivodeship level and may give significantly different results if analyzed at the level of smaller administrative units, such as municipalities. Second, the analysis is for one selected year and will not show changes over several years, which could reveal different consumer behavior depending on the changing context-air quality, amount of financing, electricity price, and other factors.
Further research by the authors will concern the behavior of prosumers in the face of further increases in energy prices and changes in government support programs, with the simultaneous intensification of educational programs increasing public awareness of the benefits and sources of green energy. The research will cover prosumers with a different demographic profile, because, as some studies in this field show [34,39,66], prosumers living in cities for whom energy bills are not a significant burden and who at the same time have a higher environmental awareness would have a completely different motivation than prosumers from rural areas for whom energy payments are a significant expense and the level of ecological awareness is significantly lower. This problem requires additional research, but the results would be an important element in the process of shaping the policy of supporting investments in green energy in Poland and the EU. In addition, the authors plan in-depth research on the design of programs supporting the financing of investments in green energy, the results of which will not only be good practice, but also specific objective measures for the evaluation of such programs on the EU scale.

Conflicts of Interest:
The authors declare no conflict of interest.