# Making Optimal Location-Sizing Decisions for Deploying Hybrid Renewable Energy at B&Bs
## 1 Introduction  
Climate change has brought various threats to humanity. Among them, global warming is arguably the most serious. According to the World Meteorological Organization, 2011-2020 was the warmest decade since the 1800s [1]. Global warming comes from human-induced emissions, mainly from burning fossil fuels [2]. As a significant contributor to the world economy, international tourism's revenue was USD 1481 billion in 2019, a 4.8% year-on-year increase [3]. However, tourism emissions increased from 3.9 to 4.5 GtCO\({}_{2}\)e between 2009 and 2013, representing 8% of global emissions [4]. Tourism can only be sustainable in the long term if it transforms into a climate-resilient industry [5]. Therefore, there is an urgent need for the tourism industry to embrace a low-carbon pathway to mitigate global warming and ultimately achieve sustainable tourism. However, sustainable tourism is a continuous process that requires seamless collaboration among tourism stakeholders, including the business, local community, government, tourists, and international community [6]. Instead of focusing on only one aspect (economic growth), sustainable tourism considers a balance between economic, environmental, and social-cultural aspects to ensure the long-term sustainability of tourism development [7]. These considerations lead the tourism industry to achieve productivity while preserving the natural environment and maintaining the quality of life. However, under a business-as-usual scenario,tourism emissions are projected to increase by 169% between 2010 and 2050 [8]. Since reducing emissions is a challenge for sustainable development, this finding recognizes that sustainability practices in the tourism industry are still insufficient [5]. Sustainable tourism should optimize environmental resources, a vital element of tourism development [9]. However, accommodation is a resource-intensive tourism subsector [10; 11]. As more than 70% of energy demand is consumed for electricity [10], accommodation is the second-highest emitter after transportation, accounting for 21% of tourism emissions [12]. This study focuses on a particular type of accommodation, bed and breakfast (B&B), which has experienced rapid growth through sharing-economy platforms [13]. As a small tourism business owned and operated by a family, a B&B is an innovative sideline business built and developed from a family's underutilized assets [14]. Unfortunately, many B&Bs have recently experienced a significant decline in guest numbers. For example, in Taiwan [15] and Northern Ireland [16], the occupancy rate was below 25% from 2013 to 2018. Oversupply and homogeneity are the reasons for this severe challenge [17; 18]. Therefore, B&Bs need to build a competitive advantage in a saturated market by differentiating themselves from the competition with novel features. Recent literature has investigated whether environmentally friendly practices in hotels (e.g., waste management, energy efficiency) can increase customer satisfaction, a critical factor in hotel selection [19]. In fact, the adoption of renewable energy (RE) as a primary energy source is the least adopted by accommodations [20]. However, B&Bs can improve energy security by changing their energy sources while reducing energy costs with a short payback period, which has been implemented in real-world applications [21]. Using low-carbon energy in tourism destinations also contributes to community economies by generating revenue, creating jobs, and diversifying income [22]. Therefore, energy transition would not only reshape a B&B's image as an eco-friendly accommodation business [23] but also facilitate the sustainable development of local communities. In addition, the shift to RE has the potential to maintain the B&B's competitive advantage by offering new service innovations continuously.