The goal of this research project is to determine if it is possible to pre-heat water for swimming pools to save energy. The study is designed to show the efficacy of this application as well as the associated energy savings. In 2016, BPA engineering collected baseline operation data on the existing electric resistance water heater for a residential swimming pool. Early in 2017, the CO2HPWH was installed and monitored. The initial results showed that the system was under performing and a number of modifications are being considered. The current plan is to implement the modifications and monitor the new design through December 2017 to allow for warm and cold weather operation. A final paper will be prepared by February 2018. While this study is focused on the residential sector, the nature and results of this study are also applicable to water heating EE projects in the commercial sector. BPA will generate a summary brief which will inform the region of the results. Its important to build the body of knowledge for CO2 heat pumps and demonstrate the efficacy of a new use case.