Understanding water-energy nexus in the provision of drinking water services is a challenge which has outstanding relevance in the current climatic emergency. Environmental efficiency and eco-efficiency assessment of water companies are two useful tools to address this challenge. In this study, we estimated hyperbolic and enhanced hyperbolic distance functions to compute the potential reduction in greenhouse gas (GHG) emissions and energy costs in the provision of drinking water. The empirical application focused on the English and Welsh water companies over 2011-2019. Average environmental efficiency and eco-efficiency scores were 0.920 and 0.962, respectively which indicates that water companies performed well but there is room for improvement. Moreover, due to the economies of scale, the cost of reducing GHG emissions was higher for water and sewerage companies than for water only companies. The results and conclusions of this study allow better understanding of the relationship between the provision of drinking water, energy costs and GHG emissions.

了解提供饮用水服务中的水能关系是一项挑战，在当前的气候紧急情况下具有突出的相关性。水公司的环境效率和生态效率评估是应对这一挑战的两个有用工具。在这项研究中，我们估计了双曲线和增强的双曲线距离函数，以计算在提供饮用水时可能减少的温室气体 (GHG) 排放和能源成本。实证应用侧重于 2011-2019 年的英国和威尔士水务公司。平均环境效率和生态效率得分分别为 0.920 和 0.962，表明水务公司表现良好，但仍有提升空间。此外，由于规模经济，供水和污水处理公司减少温室气体排放的成本高于纯供水公司。本研究的结果和结论有助于更好地理解饮用水供应、能源成本和温室气体排放之间的关系。