Publication Detail

Integrating Plug-in Electric Vehicles (PEVs) into Household Fleets - Factors Influencing Miles Traveled by PEV Owners in California (research report)

UCD-ITS-RR-21-74

Research Report

Electric Vehicle Research Center

Suggested Citation:
Chakraborty, Debapriya, Scott Hardman, Gil Tal (2021) Integrating Plug-in Electric Vehicles (PEVs) into Household Fleets - Factors Influencing Miles Traveled by PEV Owners in California (research report). Institute of Transportation Studies, University of California, Davis, Research Report UCD-ITS-RR-21-74

In this study, we investigate BEVs and PHEVs, collectively referred to as plug-in electric vehicles (PEVs). Using statistical and econometric methods, we analyze the VMT of PEVs as part of household travel demand to understand how much PEVs are being used and the factors that influence their use in a household fleet. We use data from a repeat survey of PEV owners in California. The first survey was conducted in 2015–2018, shortly after the participants purchased their PEVs, and the repeat survey, of 4,925 PEV owners, was conducted in 2019. This approach allowed us to obtain two odometer readings leading to more accurate VMT measures. Exploratory analysis of the VMT estimated from the two odometer readings suggest that BEVs were driven on average 11,250 miles per year. Long-range BEVs (>200-mile electric range) travel around 13,000 miles per year while short-range BEVs (<120 miles of electric range) travel around 10,250 miles. PHEVs in the sample traveled on average approximately 12,000 miles.
These results show that PEVs travel a similar number of miles per year as conventional vehicles. These VMT estimates are compared to measures derived from other surveys of California PEV drivers (the California Vehicle Survey and the National Household Travel survey-California Add-on) and VMT estimates obtained from loggers installed in PEVs. The VMT estimates are similar across samples exceptfor the NHTS data which shows lower PEV VMT, though the data contains a larger fraction of first-generation PEVs than the other surveys. Overall, VMT estimates from multiple surveys indicate that PEVs are driven a similar number of annual miles as gasoline vehicles (~10,800 miles). This finding has implications for emissions impact assessments of the PEV technology and predictive models of vehicular emissions.
Households in the sample used for the econometric analysis have single-vehicle or multiple cars in their fleet (multi-vehicle households) such that a PEV is used in combination with conventional fuel vehicles. The results of the econometric models analyzing the integration of PEVs in household fleets show that, PEV VMT is correlated to factors such as population density, built environment, attitudes towards technology, and lifestyle preferences. These results are similar to factors correlated with VMT with conventional vehicles. Specific to PEVs, electric driving range and access to home charging infrastructure have a major influence on PEV VMT. Electric driving range is positively correlated with VMT. This suggests that longer range BEVs, which are the dominant BEV in the market, will displace more gasoline miles than shorter range BEVs were capable of. Note that from 2018–2020, BEVs with a range of <100 miles were only 2.4% of the PEV market, and these vehicles are being phased out. The correlation of home charging to VMT further highlights the importance of home charging access: home charging is the most influential charging location in the decision to buy a BEV, is the most frequently used (3), correlates with continuing PEV ownership after adoption (4), and enables more electric vehicle miles.
Overall, our results show that PEV VMT is correlated to similar factors as conventional vehicle VMT. EV range, household electricity price, and access to level 2 charging from home are additional variables correlated with PEV VMT. The results also show that BEVs and PHEVs appear to be viable as alternatives to conventional vehicles in terms of meeting the travel needs of households.