## 2 Review of the Literature
Studies conducted in Krakow show how managing the operating time of heat pumps can significantly increase the energy self-sufficiency of homes, achieving up to 18% in monthly savings [14; 25]. This analysis proves that intelligent energy-management systems can effectively adjust the operation of devices to the current needs of users and weather conditions, resulting in reduced demand for energy from external sources. Across the European Union, with political support and subsidies, PV installations and heat pump systems are increasingly used in new construction projects, supporting the achievement of ambitious goals to reduce greenhouse gas emissions by 55% by 2030, compared to 1990 levels [26; 27]. This reflects a broader trend towards increasing energy efficiency and sustainable development. The dynamic development of PV technology in Europe, supported by favorable regulatory and financial frameworks, favors the faster adaptation of these technologies in residential and commercial projects [26]. Additionally, the increased availability and economic attractiveness of heat pumps, as well as advancements in photovoltaic technologies, open new possibilities for designers and engineers who are looking for effective ways to integrate these systems to maximize energy self-sufficiency while minimizing the negative impact on the environment. Simultaneously, the engagement of European institutions in promoting and supporting energy-sustainable solutions indicates a growing awareness of the importance of green energy in achieving not only climate goals but also in improving the quality of life of residents. Through appropriate policies and investments, it becomes possible to shape a future where sustainable construction and energy management become the standard, not the exception. According to 2023 data [28], 2.64 million heat pumps were sold in Europe. This increase in sales indicates a growing market interest in solutions that enhance the energy efficiency of buildings. Additionally, there is a steady decrease in the prices of photovoltaic panels, which results from both technological progress and increased production scale. These changes are supported by the development of new technologies that allow for the production of higher efficiency panels at lower material costs [29]. This trend is crucial because lower investment costs can contribute to faster development and broader implementation of these technologies in residential homes. This paradigm shift aims not only to increase energy efficiency but also to improve the energy self-sufficiency of residential buildings, which is significant in the context of increasing energy price volatility. The reduction in initial costs allows for faster investment payback, making such installations more accessible to a wider range of consumers. Moreover, the increased efficiency of these systems contributes to lower energy bills for end-users, which further motivates their adoption. In response to these trends, the energy policies of many European countries are increasingly focusing on supporting renewable energy initiatives, which include not only subsidies and tax incentives but also educational programs aimed at raising awareness about the benefits of using modern heating and energy production systems [29]. These market and regulatory changes demonstrate how dynamically the renewable energy sector is developing, adapting to new economic and environmental challenges. This represents an important step towards building a sustainable energy future on the European continent. These initiatives, by increasing the accessibility of eco-friendly technologies, have the potential to significantly contribute to achieving global climate goals, reducing dependency on fossil fuels, and minimizing the adverse effects of climate change. The aim of this paper is to examine the energy efficiency of combining heat pumps and photovoltaic panels in environmentally friendly buildings.