# The Impacts of Open Data and eXplainable AI on Real Estate Price Predictions in Smart Cities
## 4 Discussion
### Energy Performance Certificate  
The energy performance certificate (EPC) emerges as a significant predictor in property valuation, ranking as the third-most influential feature after PGA and Longitude, as evidenced by its substantial mean SHAP value of 15,344.33. This value underscores the significant role that energy efficiency plays in property valuation models. The SHAP beeswarm plot reinforces this, displaying a concentration of high positive SHAP values for properties with superior energy efficiency, which corresponds to lower numerical EPC ratings. This cluster of positive values on the plot illustrates a market trend where higher energy efficiency is often rewarded with higher property valuations.  
However, the plot also exhibits some negative SHAP values for EPC, although these seem to be fewer and less extreme than the positive ones. These negative values represent instances where lower energy efficiency or higher numerical EPC ratings are linked to a reduction in the predicted price. This data pattern portrays a more complex real estate market where energy efficiency is valued but not consistently across all properties. Such inconsistencies may arise from varying buyer awareness or preferences concerning energy-efficient features.  
The distribution and concentration of the SHAP values depicted in the plot capture the EPC's variable influence on property prices. The dense clustering of positive SHAP values suggests a clear correlation recognized by the model--higher energy efficiency commonly leads to higher property prices. In contrast, the scattered and less dense negative SHAP values hint at a less consistent pattern where properties with poorer energy performance are sometimes, but not consistently, associated with lower prices. This variability indicates that while energy efficiency is a crucial factor in property valuation, the extent to which it affects prices can vary, reflecting the dynamic nature of market perceptions and priorities related to energy efficiency in homes.  
Previous studies from [PERSON] et al. (2022) [65], [PERSON] et al. (2023) [44], and [PERSON] et al. (2021) [30] confirm the importance of EPC in the valuation process, and our results are aligned with these work's findings, further demonstrating that properties with higher EPC ratings tend to have a positive effect on predicted prices, reinforcing the value placed on energy efficiency in the housing market.  
The significant SHAP values associated with EPC may also indicate broader trends in the real estate market. They suggest that energy efficiency is valued and could serve as a differentiator in the market, influencing buyer preferences and property values. This finding can have implications for various stakeholders: (a) sellers might be motivated to invest in energy efficiency improvements to enhance property appeal and justify higher prices; (b) buyers may consider the EPC rating a critical factor in their decision making, valuing the long-term cost savings and environmental impact; and (c) policymakers and regulators could use these insights to promote sustainability in housing via incentives or regulations.