The introduction of plug-in electric vehicles (PEVs) represents an unprecedented interaction between the road network and electricity grid. In this new integrated system, travel demand, behavior, and traffic congestion will influence the temporal and spatial characteristics of electricity usage and environmental impacts. Furthermore, uncertainty in the transport characteristics will manifest as a new uncertainty placed on electrical infrastructure. Overall, the realized system-level impacts depend on the eventual penetration of PEV ownership. However the true market share of PEVs in the future is highly unclear and radically different scenarios are possible. This added forecasting volatility makes long-term transport models that explicitly consider travel demand uncertainty even more critical. This work utilizes transport modeling tools in order to quantify the relationship between the travel patterns of PEV drivers and PEV energy consumption rates. Furthermore, this research explicitly addresses the relationship between long term travel demand uncertainty and system level energy consumption variability, an essential issue for regional energy providers and planners. Implications are demonstrated on the Sioux Falls network.