This paper presents a series of analyses whose goal is to understand the effectiveness with which time-of-use (TOU) rates can economically incent off-peak charging in plug-in hybrid electric vehicles (PHEV). The total cost of fueling PHEV under modeled and real-world TOU rates is compared to the total cost of fueling PHEV under constant rates. Time-resolved vehicle energy consumption and fueling cost is derived for a variety of PHEV designs from travel survey data and charging behavior models. A decision tree model of PHEV consumer choices is proposed with effectiveness and cost metrics defined at each decision point. Results show that gasoline PHEV that charge off-peak incur higher gasoline costs than PHEV that charge at-will. These additional fueling costs reduce the magnitude of the economic incentives for off-peak charging that TOU rates can provide to PHEV consumers. These results are then used to compare and evaluate the effectiveness of model and real-world TOU rates and to discuss implications for modeling PHEV total fueling cost.