In 2007, NREL and Xcel Energy collaborated on an analysis study to better understand the fuel displacement potential, the costs, and the emissions impacts of market introduction of plug-in hybrid electric vehicles (PHEVs) into the Xcel Energy Colorado Service Territory. The study indicated the potential for petroleum displacement and highlighted the value of vehicle charge management to limit costs and emissions impacts.

As an extension and demonstration of the analysis results, a real-world fleet demonstration project was initiated. The purpose of the project was to 1) quantify the real-world fuel savings benefits of PHEVs, 2) gain an understanding of potential utility loading scenarios due to the introduction of PHEVs, and 3) develop and demonstrate the equipment and tools necessary for utility controlled charging. The project team successfully evaluated the performance of three vehicles placed in consumer service with charge control functions directed by Xcel Energy. Ten different charge control scenarios were explored, several of which correlated to the previous analysis study of 2007.

Analysis of 16 weeks of field study data supports the conclusions drawn in the previous study. PHEV technology holds great promise for enabling petroleum reduction in transportation. Utility controlled charge management was demonstrated and potential load profiles were generated; some of which were synchronized with renewable resources and ancillary services suggesting that utility load management of PHEVs could provide both low CO2 transportation fuel pathways and grid operational flexibility for utilities.