Despite its policy relevance, there is still a lack of empirical studies in the literature that analyze the charging behavior and driving for large samples of PHEV users. The goal of this paper is to quantify charging behavior through frequencies of overnight charging and additional charging and analyze this behavior with respect to different user groups and charging days. Moreover, this paper works to develop a method to identify charging frequencies based on daily driving distances on gasoline and electricity, which are easier to collect, compared to specific charging events. The paper also differs from previous research by using data containing a large number of users (10,488 users) with a long observation period, up to 8 years for some users, therefore providing a higher confidence level for our results. 

More specifically this paper aims to answer the following research question: What are typical frequencies for additional charging and no-overnight charging with respect to different user groups and charging days? To answer this question, the authors use an online database ( that collects real-world fuel economy data of Chevrolet Volt, a popular North American PHEV.