# Evolution of China's Building Energy Service Industry Based on Synergetic Theory
## 1 Introduction  
With the rapid economic growth and industrialization in the last decades, China has become the engine of the world's economic growth, leading to a dramatic increase in energy consumption and carbon emissions [1; 2; 3; 4]. The building sector is a critical contributor to China's energy consumption, whose energy consumption in a given life-cycle accounts for over 40% of China's total energy use and carbon emissions. Currently, more than 90% of the existing buildings in China are highly energy consumptive. Thus, China's existing building energy consumption per unit area is about two times that of developed countries under the same environmental conditions [5]. In this circumstance, there is great potential for additional energy conservation in the building sector. Since the 1980s, energy conservation has been a key point of China's development strategy due to the influence of persistent energy shortages [6; 7]. More recently, it became the main plank of China's government in terms of dealing with climate change [8; 9; 10]. The Chinese government has invested a large amount of its budget into work on energy efficiency and consumption reduction and has introduced a series of energy conservation policies, which are especially prevalent in the 13 th FYP [11; 12; 13]. However, although a series of building energy conservation policies has been published, the achievements are far from satisfactory. The government, especially the local governments, still rely on finances to promote energy-saving work because of funding shortages [14]. The Chinese government has been promoting theconcept of EPC (Energy Performance Contracting), which provides a market mechanism to deliver energy-efficient projects, including energy savings guarantees and associated design and installation services [15]. After decades of development, the ESCO industry still heavily concentrates on the industrial sector, with only 20% of the total investment in the building sector, which is far away from its potential [16]. This situation is precipitated by massive barriers that hamper the development of the building energy service industry (BESI), including a lack of scientific and rational planning, low public awareness, limited project scales, and insufficient financing channels [17; 18; 19]. BESI is composed of energy service companies, building owners, governments, building occupants, energy audit agencies, and others; thus, it is a very complex system. The operation mechanism of the BESI is a \"black box\" that involves the abovementioned stakeholders. Most previous research focused on the assessment and evaluation of the BESI, or explored the application of emerging technologies in the BESI, which neglected the BESI itself, neglecting to address aspects such as the system structure, operation mechanism, and other fundamental elements [20]. Such a lack of clarity on the theoretical issues of the BESI has led to a hindrance in the advancement of its practice. It is essential to understand the evolutionary mechanism and promote the development of the BESI to reach climate goals and energy conservation targets. Several researchers proposed the synergetic theory to explore the development of industries and apply the \"order parameter\" to determine the driving force that guides the development of the industry [21; 22; 23]. Synergetic theory proposes that all open systems can be viewed as forms of self-organization, wherein the driving force is formed through interconnection and interaction among several and even all driving force factors [22]. These driving factors are called order parameters in synergetic theory [24]. Once the order parameters are formed, they play a dominant or utilization system-related role, dominating the overall system evolution process. As a typical open system, the BESI system can be explored by synergetic theory, which is driven by the interconnection and interaction between order parameters.