Plastic recycling plays a vital role in mitigating the environmental impact of plastic waste. Life cycle assessment (LCA) is a powerful tool for evaluating the environmental performance of recycling processes, relying on accurate and transparent life cycle inventory (LCI) data. However, LCI data collection in plastic recycling poses challenges, particularly in regions with limited data availability and diverse co-products. This paper addresses the need for improved LCI data collection by proposing a thermal-based allocation method for electricity consumption in plastic recycling processes. The method considers resin-specific thermal properties during the pelletizing process and offers a more realistic estimation of resource consumption. A case study conducted in Malaysia focused on four resin types—PP, HDPE, LDPE, and LLDPE—demonstrated the effectiveness of the allocation method. The findings revealed that the conventional assumption of equal electricity consumption for all resins resulted in significant overestimation for some resins, leading to inaccurate assessments of environmental impacts. In contrast, the proposed thermal allocation method provided resin-specific estimates, improving the accuracy of electricity consumption estimation and subsequent impact assessments. The results of this study contribute to enhancing the accuracy and transparency of LCI data collection in plastic recycling processes. By considering resin-specific thermal properties, LCA practitioners can obtain more reliable estimates of electricity consumption, leading to improved assessments of environmental impacts. The study highlights the importance of standardized guidelines and approaches in LCA reference documents to ensure efficient and consistent LCI data collection.