Energy usage and its intensity are crucial factors to consider in the path towards decarbonization because they directly impact the amount of greenhouse gas emissions that are released into the atmosphere [1]. As we continue to rely on fossil fuels for energy, we emit carbon dioxide and other pollutants into the air, contributing to global warming and climate change [2]. In order to address this problem, it is necessary to reduce our energy consumption and transition to cleaner and more sustainable sources of energy [3]. This involves both increasing the efficiency of our energy usage and adopting renewable energy technologies ^[4][5][4,5].

Efficiency improvements can be achieved through a variety of measures, such as upgrading insulation in buildings [6], using energy-efficient appliances, and reducing waste in industrial processes [7]. By using energy more efficiently, we can reduce the amount of energy required to meet our needs, which in turn reduces the amount of greenhouse gas emissions generated [8]. In addition to efficiency improvements, we need to transition to cleaner sources of energy, such as wind, solar, and hydroelectric power [9]. These renewable sources of energy generate electricity without emitting greenhouse gases or other pollutants, and they have the potential to meet a significant portion of our energy needs [10]. However, the transition to renewable energy will require significant investment and infrastructure changes [11]. We need to develop new technologies, build new transmission lines, and invest in storage technologies that can help us to balance the intermittent nature of renewable energy sources [12].

Heat and fuel intensity usage in households is an important aspect of energy consumption to consider in the path towards decarbonization [13]. In most households, the primary source of heat and fuel is natural gas, which emits carbon dioxide and other greenhouse gases when burned. Reducing the intensity of heat and fuel usage in households can be achieved through a variety of measures, such as improving insulation, upgrading heating systems, and adopting more efficient appliances [14]. Improving insulation can help to reduce the amount of heat that is lost through walls, windows, and roofs, which can in turn reduce the amount of fuel needed to maintain a comfortable indoor temperature [15].

Upgrading heating systems is another important step towards reducing heat and fuel intensity usage. Older heating systems may be less efficient and may emit more greenhouse gases than newer, more efficient systems [16]. Switching to a more efficient heating system, such as a heat pump, can significantly reduce the amount of energy required to heat a home. In addition to improving insulation and upgrading heating systems, adopting more efficient appliances can also help to reduce the intensity of heat and fuel usage in households [17].

By studying the energy and heat usage patterns the household sector, it becomes possible to assess the impact of renewable resources on reducing carbon emissions and achieving decarbonization goals [18]. Renewable resources, such as solar, wind, and geothermal energy, offer cleaner alternatives to traditional fossil fuel-based energy sources. The examination of energy and heat utilization intensity provides insights into how effectively renewable resources are being incorporated and utilized in the small consumer sector [19]. It helps identify opportunities for further integration of renewable energy solutions [20], ultimately contributing to the decarbonization efforts in the Poland’s households and supporting the transition to a more sustainable energy future [21].

2. The Strategic Direction to Reduce Emissions in European Policies

Energy and fuels are vital for social and household activities, fulfilling the needs of economies in production, communication, transport, and other areas. The current trend focuses on green energy production from renewable sources, crucial for reducing greenhouse gas emissions. The European Commission has outlined this direction in the European Green Deal [1], aiming for net-zero greenhouse gas emissions by 2050 and decoupling economic growth from natural resource use. New, stricter goals for 2030 include at least a 55% reduction in greenhouse gas emissions compared to 1990. The European Union consistently implements the “Clean Energy for All Europeans” package ^[2][3][2,3], with nearly all EU leaders committing to net-zero strategies by 2050 in December 2019 [4]. The Paris Agreements initiated a new phase in climate policy, emphasizing limiting the planet’s average temperature increase. The strategic direction in the European Union countries is the development of renewable energy and heat sources, with investments in renewables and energy efficiency as a priority in the European policy.

3. Households as Energy Consumers in the European Policies

EU climate and energy policy is increasingly integrating consumers into the energy market. The current framework allows consumers to easily switch and compare energy suppliers, monitor consumption through remote reading meters, enjoy stable prices, and have access to an energy ombudsman. Households are central in the EU energy landscape, with increasing energy demands driven by higher incomes, more electrical appliances, and thermal comfort awareness. Even with efficiency improvements, such as insulated homes and low-energy appliances, total energy consumption rises [5]. In the European Union, the amount of energy consumption increased from 10,388,387.81 TJ in 2020 to 10,959,828.58 TJ in 2021 [11]. The shift to clean fuels aims to involve households as energy is a fundamental living standard. Consumers have rights, including grid access, information accessibility, and quality standards [6]. Initiatives like home renovations, photovoltaic installations, and heat pump use can reduce energy bills and environmental impacts. Residential electricity consumption in Europe accounts for 27% of total energy consumption [7]. The European climate policy package assumes consumer participation in renewable energy sources, increasing the share of renewables in the energy mix and broader electrification [8]. The EU has several programs that promote energy awareness, offer subsidies for efficient appliances [9], and promote household renewables ^[10][11][10,11]. With various regulations, EU countries aim to decrease coal energy consumption in households and boost renewable energy use ^[12][13][12,13]. These efforts enhance EU energy security and drive towards climate goals [14]. Embracing innovative solutions and promoting household energy efficiency are vital for sustainable energy progress ^[15][16][15,16]. As markets evolve, consumers have diverse energy choices and can become prosumers, benefiting from real-time energy information in smart cities and achieving independence from fluctuating market prices [17]. The push for increased energy efficiency is a strategic climate policy goal [18], encouraging consumers to participate in energy markets directly. This activation fosters the transition from consumer to prosumer, influenced by varying economic developments [19].

4. Active Small Consumers in the Energy Market

In recent years, the European Commission has been promoting transparency in the carbon footprint of products for consumer awareness [20]. Technological advancements have allowed consumers to diversify their energy sources. A consumer-centered market model was proposed in 2015, aiming to connect consumers closely with wholesale and retail markets [20]. This model supports consumers in managing their energy consumption, leading to savings and contributing to climate transformation [21]. Enabling flexible consumption involves access to price signals and incentives such as lower tariffs for reduced consumption during network congestion ^{[20][21][22][23]}[20,21,22,23]. Decentralization of the energy market leads to reduced generation-consumption distance, and the microgrid sector is witnessing strong growth worldwide [24]. The decentralized model employs a ‘peer-to-peer’ principle [25]. Prosumers, as producers and consumers of energy, play a crucial role in reducing energy usage and promoting sustainability [26]. They generate energy through renewable sources, implement energy-saving measures, and can participate in demand response programs and community energy sharing initiatives [27], thus contributing to a reduced reliance on fossil fuels and increased sustainability [28].

5. Small Consumer in the Industry 4.0 and Smart Cities

Growing environmental awareness in electricity and heat consumers influences proper (sustainable) choices [29]. Climate consciousness is a key part of this awareness, allowing for purposeful activity and anticipation of environmental results [29]. The growing awareness in society leads to self-sufficiency from renewable sources, contributes to increased fuel efficiency at the household level, and fosters attitudes toward high-tech energy solutions [30]. Prosumers, who are the green group of the Polish households, show consistency in ecological behavior, such as turning off lights, buying energy-efficient appliances, and using them in ways that limit consumption [30]. This characterizes a high awareness of reducing heat and electricity consumption [30]. New technologies of the Fourth Industrial Revolution, such as the development of ICT and smart energy supply networks, ease consumer control over energy and heat consumption ^[31][32][31,32]. This is further supported by home digitization (e.g., smart homes) and the necessity to protect privacy through data standards and safety mitigation systems ^[33][34][33,34]. Industry 4.0 technologies can significantly decrease energy usage among prosumers [35]. They enable smart energy management that monitors real-time consumption [36] and adjusts energy usage based on demand [37]. Predictive maintenance [38], utilizing artificial intelligence (AI) [39] and machine learning, helps in scheduling maintenance before breakdowns [40]. Optimization in supply chain management [41], development of smart buildings [42], and manufacturing energy-efficient products [42] contribute to reducing energy waste [43]. The development of smart buildings is another key aspect of sustainability and innovation [44]. Smart buildings are designed to intelligently manage energy consumption by utilizing sensors and automation systems [45]. These technologies ensure that lighting [46], heating [47], and cooling systems [48] are only active when necessary, leading to reduced energy waste [48]. Moreover, smart buildings often incorporate renewable energy sources such as solar panels [49] and efficient insulation materials, further contributing to a sustainable future [50]. Sustainability has become deeply intertwined with the concepts of Industry 4.0 and the emerging Industry 5.0 [51]. These industrial revolutions prioritize the integration of advanced technologies, such as the IoT [52], AI [53], and automation [54]. In doing so, they aim to create smarter, more efficient, and environmentally conscious production processes [55]. By harnessing the power of digitalization [56] and real-time data analysis [57], industries are better equipped to optimize their operations, minimize waste, and make sustainable choices throughout their value chains [58]. This alignment of technology and sustainability is essential in shaping a more eco-friendly and responsible future for industrial sectors worldwide [59]. Smart cities serve as instrumental hubs for prosumers, a term used to describe individuals and businesses that actively participate in both energy production and consumption, facilitating their journey towards achieving decarbonization goals [60]. This emerging paradigm shift in energy management is critical in the broader context of sustainable urban development [61]. Prosumers contribute to the energy landscape by producing renewable energy through technologies like solar panels and wind turbines while simultaneously consuming energy for various purposes ^[62][63][62,63]. Smart cities empower these prosumers with a suite of tools and services designed to enhance their energy efficiency and reduce their carbon footprint [64]. Smart grids are a fundamental component of the prosumer-driven energy ecosystem within smart cities [65]. These grids are designed to be flexible and responsive [66], allowing prosumers to not only draw electricity from the grid but also sell excess energy they generate back to it [67]. This dynamic interaction encourages the use of renewable energy sources, as prosumers are incentivized to generate surplus green energy [68]. Additionally, smart grids offer energy storage solutions, such as batteries [69], which prosumers can use to store excess energy for later use or to sell it during peak demand periods. They can also implement demand response programs [69], provide real-time data on energy usage [70], and offer mobility solutions like electric bike-sharing to reduce emissions [71]. By facilitating renewable energy integration, optimizing energy use, and promoting sustainable mobility [72], smart cities help prosumers become more energy-efficient, reduce their carbon footprint, and contribute to a more sustainable future [73].

6. Trends and Developments in the Small Consumer Market

For consumers to benefit financially from new opportunities, they need to have access to smart systems and to electricity and heat supply contracts based on dynamic prices linked to the market [74]. In addition to consumers adapting their consumption to price signals [75], new offtake response services are now emerging [76], where market players offer an aggregation and management service for fuel consumption, paying them compensation for flexibility ^[77][78][77,78]. Recently, the following trends can be observed in markets where consumers (households/small consumer market) are actively involved:

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saving energy and heat by investing in technologies that provide energy from renewable sources (own renewable energy and heat sources),

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the need to purchase boilers that reduce CO₂ emissions (certified boilers),

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thanks to the internet and new “smart” technologies, citizens’ access to information and services in a diversified energy and heat market is increasing,

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solutions offered by energy technology and transmission network service providers are increasingly personalized, and

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legal protection of consumer rights.

These directions are included in the package of documents entitled “Clean Energy for All Europeans”. In the small consumer sector, the key trends, driving regulations seeking to change consumer perceptions of electricity and heat, are as follows:

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market liberalization and high prices for energy and fuels produced from coal [79],

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increased demand for renewable energy (transitioning towards clean energy and a low-carbon/zero-carbon economy by 2050) [80],

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increasing climate awareness of consumers,

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increased share of distributed energy sources in the total market,

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consumers’ access to various forms of energy and heat savings,

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increased proportion of network usage charges and taxes, and in particular additional charges in the final household electricity and heat bills [81], and

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houses and network modernization and infrastructure investments using smart technologies [82].

The small consumer sector, such as households and small businesses, can achieve a better level of decarbonization by taking several actions [83]. Small consumers can reduce their carbon footprint by decreasing their energy consumption [84]. This can be achieved by using energy-efficient appliances and light bulbs, turning off electronics when not in use, and improving insulation and weatherization of their homes. They can switch to renewable energy sources such as solar, wind [85], or geothermal power or purchasing green energy from a provider [86]. Small consumers can reduce their carbon footprint by using sustainable modes of transportation such as walking, cycling, or using public transport instead of driving a car. They can also switch to electric or hybrid vehicles [87]. This group of consumers can reduce their carbon footprint by reducing waste and recycling as much as possible. They can also compost organic waste and avoid single-use products [88]. Small consumers can advocate for policies that promote sustainable practices and educate their communities on the importance of decarbonization [89]. They can join local environmental organizations [90], attend community events [91], and engage in conversations with their peers and policymakers ^[92][93][92,93]. Poland’s inclusion in these trends is necessary and inevitable, both because of the Paris Agreement, to which Poland is a signatory, and because of its membership of the European Union and the need to become involved in the implementation of European energy policy. It is also necessary due to the increasing level of awareness among the public to reduce emissions from coal combustion. For years, the Polish energy sector has been based on indigenous energy resources, namely hard coal and lignite. Electricity generation in Poland takes place primarily in thermal power plants fired by hard coal and lignite (over 70% of energy in Poland is generated from coal) [94]. The size of resources varies from year to year not only as a result of exploitation and changes in the recognition and documentation of resources, but also as a consequence of changes in the assessment of the resources of developed mineral deposits resulting from the principles of market economy and restructuring activities (out of 160 hard coal resources in Poland, 64 were undeveloped in 2018) [95]. A significant part of thermal coal mines is unprofitable due to difficult mining and geological conditions and irrational organization of work. The closure of mines in Poland has been going on for three decades. Compared to the 1990s, the number of mines has decreased from 70 to 21 and coal production has fallen from almost 180 million tons to less than 62 million tons (2019) [96]. In 2021, Poland also decided that the last thermal coal mine will close in 2049 [97]. By reducing coal mining, the Polish government plans to build a nuclear power plant (the first in Poland). In addition, the Polish energy plan (until 2030) assumes a strong diversification of energy sources and investment in renewable energy technologies [98]. The Polish Energy Policy is subordinated to the policies of the EU, of which Poland is a member. The Polish Energy Policy until 2030 is a priority in the area of energy and heat management [99].